Ported micro feature generation for speech to micro framework

PiperOrigin-RevId: 234230415

tensorflow/lite/experimental/micro/examples/micro_speech/BUILD

@@ -11,34 +11,34 @@ load(
 )
 
 cc_library(
-    name = "model_settings",
+    name = "simple_model_settings",
     srcs = [
-        "model_settings.cc",
+        "simple_features/simple_model_settings.cc",
     ],
     hdrs = [
-        "model_settings.h",
+        "simple_features/simple_model_settings.h",
     ],
 )
 
 cc_library(
-    name = "tiny_conv_model_data",
+    name = "tiny_conv_simple_features_model_data",
     srcs = [
-        "tiny_conv_model_data.cc",
+        "simple_features/tiny_conv_simple_features_model_data.cc",
     ],
     hdrs = [
-        "tiny_conv_model_data.h",
+        "simple_features/tiny_conv_simple_features_model_data.h",
     ],
 )
 
 cc_library(
-    name = "features_test_data",
+    name = "simple_features_test_data",
     srcs = [
-        "no_features_data.cc",
+        "simple_features/no_simple_features_data.cc",
-        "yes_features_data.cc",
+        "simple_features/yes_simple_features_data.cc",
     ],
     hdrs = [
-        "no_features_data.h",
+        "simple_features/no_simple_features_data.h",
-        "yes_features_data.h",
+        "simple_features/yes_simple_features_data.h",
     ],
 )
 
@@ -48,10 +48,10 @@ tflite_micro_cc_test(
         "micro_speech_test.cc",
     ],
     deps = [
-        ":features_test_data",
-        ":tiny_conv_model_data",
         "//tensorflow/lite:schema_fbs_version",
         "//tensorflow/lite/experimental/micro:micro_framework",
+        "//tensorflow/lite/experimental/micro/examples/micro_speech/micro_features:micro_features_test_data",
+        "//tensorflow/lite/experimental/micro/examples/micro_speech/micro_features:tiny_conv_micro_features_model_data",
         "//tensorflow/lite/experimental/micro/kernels:all_ops_resolver",
         "//tensorflow/lite/experimental/micro/kernels:micro_ops",
         "//tensorflow/lite/experimental/micro/testing:micro_test",
@@ -60,45 +60,66 @@ tflite_micro_cc_test(
 )
 
 cc_library(
-    name = "preprocessor_test_data",
+    name = "audio_sample_test_data",
     srcs = [
         "no_30ms_sample_data.cc",
-        "no_power_spectrum_data.cc",
         "yes_30ms_sample_data.cc",
-        "yes_power_spectrum_data.cc",
     ],
     hdrs = [
         "no_30ms_sample_data.h",
-        "no_power_spectrum_data.h",
         "yes_30ms_sample_data.h",
-        "yes_power_spectrum_data.h",
     ],
 )
 
 cc_library(
-    name = "preprocessor_reference",
+    name = "audio_large_sample_test_data",
     srcs = [
-        "preprocessor.cc",
+        "no_1000ms_sample_data.cc",
+        "yes_1000ms_sample_data.cc",
     ],
     hdrs = [
-        "preprocessor.h",
+        "no_1000ms_sample_data.h",
+        "yes_1000ms_sample_data.h",
+    ],
+)
+
+cc_library(
+    name = "simple_features_generator_test_data",
+    srcs = [
+        "simple_features/no_power_spectrum_data.cc",
+        "simple_features/yes_power_spectrum_data.cc",
+    ],
+    hdrs = [
+        "simple_features/no_power_spectrum_data.h",
+        "simple_features/yes_power_spectrum_data.h",
+    ],
+)
+
+cc_library(
+    name = "simple_features_generator_reference",
+    srcs = [
+        "simple_features/simple_features_generator.cc",
+    ],
+    hdrs = [
+        "simple_features/simple_features_generator.h",
     ],
     deps = [
-        ":model_settings",
+        ":simple_model_settings",
         "//tensorflow/lite/c:c_api_internal",
         "//tensorflow/lite/experimental/micro:micro_framework",
     ],
 )
 
 tflite_micro_cc_test(
-    name = "preprocessor_reference_test",
+    name = "simple_features_generator_reference_test",
     srcs = [
-        "preprocessor_test.cc",
+        "simple_features/simple_features_generator_test.cc",
     ],
     deps = [
-        ":model_settings",
+        ":audio_sample_test_data",
-        ":preprocessor_reference",
+        ":simple_features_generator_reference",
-        ":preprocessor_test_data",
+        ":simple_features_generator_test_data",
+        ":simple_model_settings",
         "//tensorflow/lite/c:c_api_internal",
         "//tensorflow/lite/experimental/micro:micro_framework",
         "//tensorflow/lite/experimental/micro/testing:micro_test",
@@ -106,29 +127,30 @@ tflite_micro_cc_test(
 )
 
 cc_library(
-    name = "preprocessor_fixed",
+    name = "simple_features_generator_fixed",
     srcs = [
-        "fixed_point/preprocessor.cc",
+        "simple_features/fixed_point/simple_features_generator.cc",
     ],
     hdrs = [
-        "preprocessor.h",
+        "simple_features/simple_features_generator.h",
     ],
     deps = [
-        ":model_settings",
+        ":simple_model_settings",
         "//tensorflow/lite/c:c_api_internal",
         "//tensorflow/lite/experimental/micro:micro_framework",
     ],
 )
 
 tflite_micro_cc_test(
-    name = "preprocessor_fixed_test",
+    name = "simple_features_generator_fixed_test",
     srcs = [
-        "preprocessor_test.cc",
+        "simple_features/simple_features_generator_test.cc",
     ],
     deps = [
-        ":model_settings",
+        ":audio_sample_test_data",
-        ":preprocessor_fixed",
+        ":simple_features_generator_fixed",
-        ":preprocessor_test_data",
+        ":simple_features_generator_test_data",
+        ":simple_model_settings",
         "//tensorflow/lite/c:c_api_internal",
         "//tensorflow/lite/experimental/micro:micro_framework",
         "//tensorflow/lite/experimental/micro/testing:micro_test",
@@ -144,9 +166,25 @@ cc_library(
         "audio_provider.h",
     ],
     deps = [
-        ":model_settings",
         "//tensorflow/lite/c:c_api_internal",
         "//tensorflow/lite/experimental/micro:micro_framework",
+        "//tensorflow/lite/experimental/micro/examples/micro_speech/micro_features:micro_model_settings",
+    ],
+)
+
+cc_library(
+    name = "audio_provider_mock",
+    srcs = [
+        "audio_provider_mock.cc",
+    ],
+    hdrs = [
+        "audio_provider.h",
+    ],
+    deps = [
+        ":audio_large_sample_test_data",
+        "//tensorflow/lite/c:c_api_internal",
+        "//tensorflow/lite/experimental/micro:micro_framework",
+        "//tensorflow/lite/experimental/micro/examples/micro_speech/micro_features:micro_model_settings",
     ],
 )
 
@@ -157,9 +195,24 @@ tflite_micro_cc_test(
     ],
     deps = [
         ":audio_provider",
-        ":model_settings",
         "//tensorflow/lite/c:c_api_internal",
         "//tensorflow/lite/experimental/micro:micro_framework",
+        "//tensorflow/lite/experimental/micro/examples/micro_speech/micro_features:micro_model_settings",
+        "//tensorflow/lite/experimental/micro/testing:micro_test",
+    ],
+)
+
+tflite_micro_cc_test(
+    name = "audio_provider_mock_test",
+    srcs = [
+        "audio_provider_mock_test.cc",
+    ],
+    deps = [
+        ":audio_large_sample_test_data",
+        ":audio_provider_mock",
+        "//tensorflow/lite/c:c_api_internal",
+        "//tensorflow/lite/experimental/micro:micro_framework",
+        "//tensorflow/lite/experimental/micro/examples/micro_speech/micro_features:micro_model_settings",
         "//tensorflow/lite/experimental/micro/testing:micro_test",
     ],
 )
@@ -174,10 +227,10 @@ cc_library(
     ],
     deps = [
         ":audio_provider",
-        ":model_settings",
-        ":preprocessor_reference",
         "//tensorflow/lite/c:c_api_internal",
         "//tensorflow/lite/experimental/micro:micro_framework",
+        "//tensorflow/lite/experimental/micro/examples/micro_speech/micro_features:micro_features_generator",
+        "//tensorflow/lite/experimental/micro/examples/micro_speech/micro_features:micro_model_settings",
     ],
 )
 
@@ -189,9 +242,41 @@ tflite_micro_cc_test(
     deps = [
         ":audio_provider",
         ":feature_provider",
-        ":model_settings",
         "//tensorflow/lite/c:c_api_internal",
         "//tensorflow/lite/experimental/micro:micro_framework",
+        "//tensorflow/lite/experimental/micro/examples/micro_speech/micro_features:micro_model_settings",
+        "//tensorflow/lite/experimental/micro/testing:micro_test",
+    ],
+)
+
+cc_library(
+    name = "feature_provider_mock",
+    srcs = [
+        "feature_provider.cc",
+    ],
+    hdrs = [
+        "feature_provider.h",
+    ],
+    deps = [
+        ":audio_provider_mock",
+        "//tensorflow/lite/c:c_api_internal",
+        "//tensorflow/lite/experimental/micro:micro_framework",
+        "//tensorflow/lite/experimental/micro/examples/micro_speech/micro_features:micro_features_generator",
+        "//tensorflow/lite/experimental/micro/examples/micro_speech/micro_features:micro_model_settings",
+    ],
+)
+
+tflite_micro_cc_test(
+    name = "feature_provider_mock_test",
+    srcs = [
+        "feature_provider_mock_test.cc",
+    ],
+    deps = [
+        ":feature_provider_mock",
+        "//tensorflow/lite/c:c_api_internal",
+        "//tensorflow/lite/experimental/micro:micro_framework",
+        "//tensorflow/lite/experimental/micro/examples/micro_speech/micro_features:micro_features_test_data",
+        "//tensorflow/lite/experimental/micro/examples/micro_speech/micro_features:micro_model_settings",
         "//tensorflow/lite/experimental/micro/testing:micro_test",
     ],
 )
@@ -205,9 +290,9 @@ cc_library(
         "recognize_commands.h",
     ],
     deps = [
-        ":model_settings",
         "//tensorflow/lite/c:c_api_internal",
         "//tensorflow/lite/experimental/micro:micro_framework",
+        "//tensorflow/lite/experimental/micro/examples/micro_speech/micro_features:micro_model_settings",
     ],
 )
 
@@ -235,11 +320,29 @@ cc_binary(
     deps = [
         ":audio_provider",
         ":feature_provider",
-        ":model_settings",
         ":recognize_commands",
-        ":tiny_conv_model_data",
         "//tensorflow/lite:schema_fbs_version",
         "//tensorflow/lite/experimental/micro:micro_framework",
+        "//tensorflow/lite/experimental/micro/examples/micro_speech/micro_features:micro_model_settings",
+        "//tensorflow/lite/experimental/micro/examples/micro_speech/micro_features:tiny_conv_micro_features_model_data",
+        "//tensorflow/lite/experimental/micro/kernels:all_ops_resolver",
+        "//tensorflow/lite/schema:schema_fbs",
+    ],
+)
+
+cc_binary(
+    name = "micro_speech_mock",
+    srcs = [
+        "main.cc",
+    ],
+    deps = [
+        ":audio_provider_mock",
+        ":feature_provider",
+        ":recognize_commands",
+        "//tensorflow/lite:schema_fbs_version",
+        "//tensorflow/lite/experimental/micro:micro_framework",
+        "//tensorflow/lite/experimental/micro/examples/micro_speech/micro_features:micro_model_settings",
+        "//tensorflow/lite/experimental/micro/examples/micro_speech/micro_features:tiny_conv_micro_features_model_data",
         "//tensorflow/lite/experimental/micro/kernels:all_ops_resolver",
         "//tensorflow/lite/schema:schema_fbs",
     ],

tensorflow/lite/experimental/micro/examples/micro_speech/CMSIS/Makefile.inc

@@ -17,6 +17,7 @@ ifneq ($(filter CMSIS,$(ALL_TAGS)),)
   CMSIS_PREPROCESSOR_HDRS := \
     tensorflow/lite/experimental/micro/examples/micro_speech/CMSIS/hanning.h \
     tensorflow/lite/experimental/micro/examples/micro_speech/CMSIS/sin_1k.h \
+    third_party/CMSIS_ext/README.md \
     third_party/CMSIS_ext/arm_cmplx_mag_squared_q10p6.h
 
   PREPROCESSOR_TEST_SRCS += $(CMSIS_PREPROCESSOR_SRCS)
@@ -43,6 +44,7 @@ ifneq ($(filter CMSIS,$(ALL_TAGS)),)
     $(MAKEFILE_DIR)/downloads/cmsis/CMSIS/DSP/Source/StatisticsFunctions/arm_max_q7.c
 
   THIRD_PARTY_CC_HDRS += \
+    third_party/cmsis/LICENSE.txt \
     third_party/cmsis/CMSIS/Core/Include/cmsis_compiler.h \
     third_party/cmsis/CMSIS/Core/Include/cmsis_gcc.h \
     third_party/cmsis/CMSIS/Core/Include/cmsis_version.h \

tensorflow/lite/experimental/micro/examples/micro_speech/Makefile.inc

@@ -1,106 +1,349 @@
 
+INCLUDES += \
+ -I$(MAKEFILE_DIR)/downloads/kissfft
+
+PROJECT_INCLUDES += \
+third_party/kissfft
+
+KISSFFT_LIB_SRCS := \
+$(MAKEFILE_DIR)/downloads/kissfft/kiss_fft.c \
+$(MAKEFILE_DIR)/downloads/kissfft/tools/kiss_fftr.c
+
+KISSFFT_LIB_HDRS := \
+$(MAKEFILE_DIR)/downloads/kissfft/COPYING \
+$(MAKEFILE_DIR)/downloads/kissfft/kiss_fft.h \
+$(MAKEFILE_DIR)/downloads/kissfft/_kiss_fft_guts.h \
+$(MAKEFILE_DIR)/downloads/kissfft/tools/kiss_fftr.h
+
 MICRO_SPEECH_TEST_SRCS := \
 tensorflow/lite/experimental/micro/examples/micro_speech/micro_speech_test.cc \
-tensorflow/lite/experimental/micro/examples/micro_speech/tiny_conv_model_data.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/tiny_conv_micro_features_model_data.cc \
-tensorflow/lite/experimental/micro/examples/micro_speech/no_features_data.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/no_micro_features_data.cc \
-tensorflow/lite/experimental/micro/examples/micro_speech/yes_features_data.cc
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/yes_micro_features_data.cc
 
 MICRO_SPEECH_TEST_HDRS := \
-tensorflow/lite/experimental/micro/examples/micro_speech/tiny_conv_model_data.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/tiny_conv_micro_features_model_data.h \
-tensorflow/lite/experimental/micro/examples/micro_speech/no_features_data.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/no_micro_features_data.h \
-tensorflow/lite/experimental/micro/examples/micro_speech/yes_features_data.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/yes_micro_features_data.h \
 
-PREPROCESSOR_TEST_SRCS := \
+SIMPLE_FEATURES_GENERATOR_TEST_SRCS := \
-tensorflow/lite/experimental/micro/examples/micro_speech/preprocessor.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/simple_features_generator.cc \
-tensorflow/lite/experimental/micro/examples/micro_speech/preprocessor_test.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/simple_features_generator_test.cc \
 tensorflow/lite/experimental/micro/examples/micro_speech/no_30ms_sample_data.cc \
 tensorflow/lite/experimental/micro/examples/micro_speech/yes_30ms_sample_data.cc \
-tensorflow/lite/experimental/micro/examples/micro_speech/no_power_spectrum_data.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/no_power_spectrum_data.cc \
-tensorflow/lite/experimental/micro/examples/micro_speech/yes_power_spectrum_data.cc
+tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/yes_power_spectrum_data.cc
 
-PREPROCESSOR_TEST_HDRS := \
+SIMPLE_FEATURES_GENERATOR_TEST_HDRS := \
-tensorflow/lite/experimental/micro/examples/micro_speech/preprocessor.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/simple_model_settings.h \
-tensorflow/lite/experimental/micro/examples/micro_speech/model_settings.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/simple_features_generator.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/no_30ms_sample_data.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/yes_30ms_sample_data.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/no_power_spectrum_data.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/yes_power_spectrum_data.h
+
+MICRO_FEATURES_LIB_SRCS := \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/fft.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/fft_util.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/filterbank.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/filterbank_util.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/frontend.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/frontend_util.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/log_lut.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/log_scale.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/log_scale_util.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/noise_reduction.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/noise_reduction_util.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/pcan_gain_control.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/pcan_gain_control_util.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/window.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/window_util.cc \
+$(KISSFFT_LIB_SRCS)
+
+MICRO_FEATURES_LIB_HDRS := \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/bits.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/fft.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/fft_util.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/filterbank.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/filterbank_util.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/frontend.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/frontend_util.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/log_lut.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/log_scale.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/log_scale_util.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/noise_reduction.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/noise_reduction_util.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/no_micro_features_data.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/pcan_gain_control.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/pcan_gain_control_util.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/static_alloc.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/window.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/window_util.h \
+$(KISSFFT_LIB_HDRS)
+
+MICRO_FEATURES_FFT_TEST_SRCS := \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/fft_test.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/fft.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/fft_util.cc \
+$(KISSFFT_LIB_SRCS)
+
+MICRO_FEATURES_FFT_TEST_HDRS := \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/fft.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/fft_util.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/static_alloc.h \
+$(KISSFFT_LIB_HDRS)
+
+MICRO_FEATURES_FILTERBANK_TEST_SRCS := \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/filterbank_test.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/filterbank.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/filterbank_util.cc
+
+MICRO_FEATURES_FILTERBANK_TEST_HDRS := \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/filterbank.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/filterbank_util.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/static_alloc.h
+
+MICRO_FEATURES_FRONTEND_TEST_SRCS := \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/frontend_test.cc \
+$(MICRO_FEATURES_LIB_SRCS)
+
+MICRO_FEATURES_FRONTEND_TEST_HDRS := \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/frontend.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/frontend_util.h \
+$(MICRO_FEATURES_LIB_HDRS)
+
+MICRO_FEATURES_LOG_SCALE_TEST_SRCS := \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/log_scale_test.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/log_lut.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/log_scale.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/log_scale_util.cc
+
+MICRO_FEATURES_LOG_SCALE_TEST_HDRS := \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/log_lut.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/log_scale.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/log_scale_util.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/bits.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/static_alloc.h
+
+MICRO_FEATURES_NOISE_REDUCTION_TEST_SRCS := \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/noise_reduction_test.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/noise_reduction.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/noise_reduction_util.cc
+
+MICRO_FEATURES_NOISE_REDUCTION_TEST_HDRS := \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/noise_reduction.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/noise_reduction_util.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/static_alloc.h
+
+MICRO_FEATURES_PCAN_GAIN_CONTROL_TEST_SRCS := \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/pcan_gain_control_test.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/pcan_gain_control.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/pcan_gain_control_util.cc
+
+MICRO_FEATURES_PCAN_GAIN_CONTROL_TEST_HDRS := \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/pcan_gain_control.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/pcan_gain_control_util.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/static_alloc.h
+
+MICRO_FEATURES_WINDOW_TEST_SRCS := \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/window_test.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/window.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/window_util.cc
+
+MICRO_FEATURES_WINDOW_TEST_HDRS := \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/window.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/window_util.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/static_alloc.h
+
+MICRO_FEATURES_GENERATOR_SRCS := \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/micro_features_generator.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/micro_model_settings.cc \
+$(MICRO_FEATURES_LIB_SRCS)
+
+MICRO_FEATURES_GENERATOR_HDRS := \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/micro_features_generator.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/micro_model_settings.h \
+$(MICRO_FEATURES_LIB_HDRS)
+
+MICRO_FEATURES_GENERATOR_TEST_SRCS := \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/micro_features_generator_test.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/no_feature_data_slice.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/yes_feature_data_slice.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/no_30ms_sample_data.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/yes_30ms_sample_data.cc \
+$(MICRO_FEATURES_GENERATOR_SRCS)
+
+MICRO_FEATURES_GENERATOR_TEST_HDRS := \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/no_feature_data_slice.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/yes_feature_data_slice.h \
 tensorflow/lite/experimental/micro/examples/micro_speech/no_30ms_sample_data.h \
 tensorflow/lite/experimental/micro/examples/micro_speech/yes_30ms_sample_data.h \
-tensorflow/lite/experimental/micro/examples/micro_speech/no_power_spectrum_data.h \
+$(MICRO_FEATURES_GENERATOR_HDRS)
-tensorflow/lite/experimental/micro/examples/micro_speech/yes_power_spectrum_data.h
 
 AUDIO_PROVIDER_TEST_SRCS := \
 tensorflow/lite/experimental/micro/examples/micro_speech/audio_provider_test.cc \
-tensorflow/lite/experimental/micro/examples/micro_speech/model_settings.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/micro_model_settings.cc \
 tensorflow/lite/experimental/micro/examples/micro_speech/audio_provider.cc
 
 AUDIO_PROVIDER_TEST_HDRS := \
-tensorflow/lite/experimental/micro/examples/micro_speech/model_settings.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/micro_model_settings.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/audio_provider.h \
+
+AUDIO_PROVIDER_MOCK_TEST_SRCS := \
+tensorflow/lite/experimental/micro/examples/micro_speech/audio_provider_mock_test.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/micro_model_settings.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/no_1000ms_sample_data.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/yes_1000ms_sample_data.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/audio_provider_mock.cc
+
+AUDIO_PROVIDER_MOCK_TEST_HDRS := \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/micro_model_settings.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/no_1000ms_sample_data.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/yes_1000ms_sample_data.h \
 tensorflow/lite/experimental/micro/examples/micro_speech/audio_provider.h \
 
 FEATURE_PROVIDER_TEST_SRCS := \
 tensorflow/lite/experimental/micro/examples/micro_speech/feature_provider_test.cc \
-tensorflow/lite/experimental/micro/examples/micro_speech/model_settings.cc \
 tensorflow/lite/experimental/micro/examples/micro_speech/audio_provider.cc \
-tensorflow/lite/experimental/micro/examples/micro_speech/preprocessor.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/feature_provider.cc \
-tensorflow/lite/experimental/micro/examples/micro_speech/feature_provider.cc
+$(MICRO_FEATURES_GENERATOR_SRCS)
 
 FEATURE_PROVIDER_TEST_HDRS := \
-tensorflow/lite/experimental/micro/examples/micro_speech/model_settings.h \
 tensorflow/lite/experimental/micro/examples/micro_speech/audio_provider.h \
-tensorflow/lite/experimental/micro/examples/micro_speech/preprocessor.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/feature_provider.h \
-tensorflow/lite/experimental/micro/examples/micro_speech/feature_provider.h
+$(MICRO_FEATURES_GENERATOR_HDRS)
+
+FEATURE_PROVIDER_MOCK_TEST_SRCS := \
+tensorflow/lite/experimental/micro/examples/micro_speech/feature_provider_test.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/audio_provider_mock.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/no_1000ms_sample_data.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/yes_1000ms_sample_data.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/feature_provider.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/no_micro_features_data.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/yes_micro_features_data.cc \
+$(MICRO_FEATURES_GENERATOR_SRCS)
+
+FEATURE_PROVIDER_MOCK_TEST_HDRS := \
+tensorflow/lite/experimental/micro/examples/micro_speech/audio_provider.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/no_1000ms_sample_data.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/yes_1000ms_sample_data.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/feature_provider.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/no_micro_features_data.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/yes_micro_features_data.h \
+$(MICRO_FEATURES_GENERATOR_HDRS)
 
 RECOGNIZE_COMMANDS_TEST_SRCS := \
 tensorflow/lite/experimental/micro/examples/micro_speech/recognize_commands_test.cc \
-tensorflow/lite/experimental/micro/examples/micro_speech/model_settings.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/micro_model_settings.cc \
 tensorflow/lite/experimental/micro/examples/micro_speech/recognize_commands.cc
 
 RECOGNIZE_COMMANDS_TEST_HDRS := \
-tensorflow/lite/experimental/micro/examples/micro_speech/model_settings.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/micro_model_settings.h \
 tensorflow/lite/experimental/micro/examples/micro_speech/recognize_commands.h
 
 MICRO_SPEECH_SRCS := \
 tensorflow/lite/experimental/micro/examples/micro_speech/main.cc \
-tensorflow/lite/experimental/micro/examples/micro_speech/model_settings.cc \
 tensorflow/lite/experimental/micro/examples/micro_speech/audio_provider.cc \
 tensorflow/lite/experimental/micro/examples/micro_speech/feature_provider.cc \
-tensorflow/lite/experimental/micro/examples/micro_speech/preprocessor.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/no_micro_features_data.cc \
-tensorflow/lite/experimental/micro/examples/micro_speech/no_features_data.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/yes_micro_features_data.cc \
-tensorflow/lite/experimental/micro/examples/micro_speech/yes_features_data.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/tiny_conv_micro_features_model_data.cc \
-tensorflow/lite/experimental/micro/examples/micro_speech/tiny_conv_model_data.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/recognize_commands.cc \
-tensorflow/lite/experimental/micro/examples/micro_speech/recognize_commands.cc
+$(MICRO_FEATURES_GENERATOR_SRCS)
 
 MICRO_SPEECH_HDRS := \
-tensorflow/lite/experimental/micro/examples/micro_speech/model_settings.h \
 tensorflow/lite/experimental/micro/examples/micro_speech/audio_provider.h \
 tensorflow/lite/experimental/micro/examples/micro_speech/feature_provider.h \
-tensorflow/lite/experimental/micro/examples/micro_speech/preprocessor.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/no_micro_features_data.h \
-tensorflow/lite/experimental/micro/examples/micro_speech/no_features_data.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/yes_micro_features_data.h \
-tensorflow/lite/experimental/micro/examples/micro_speech/yes_features_data.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/tiny_conv_micro_features_model_data.h \
-tensorflow/lite/experimental/micro/examples/micro_speech/tiny_conv_model_data.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/recognize_commands.h \
-tensorflow/lite/experimental/micro/examples/micro_speech/recognize_commands.h
+$(MICRO_FEATURES_GENERATOR_HDRS)
+
+MICRO_SPEECH_MOCK_SRCS := \
+tensorflow/lite/experimental/micro/examples/micro_speech/main.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/audio_provider_mock.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/no_1000ms_sample_data.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/yes_1000ms_sample_data.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/feature_provider.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/no_micro_features_data.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/yes_micro_features_data.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/tiny_conv_micro_features_model_data.cc \
+tensorflow/lite/experimental/micro/examples/micro_speech/recognize_commands.cc \
+$(MICRO_FEATURES_GENERATOR_SRCS)
+
+MICRO_SPEECH_MOCK_HDRS := \
+tensorflow/lite/experimental/micro/examples/micro_speech/audio_provider.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/no_1000ms_sample_data.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/yes_1000ms_sample_data.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/feature_provider.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/micro_features_generator.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/no_micro_features_data.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/yes_micro_features_data.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/tiny_conv_micro_features_model_data.h \
+tensorflow/lite/experimental/micro/examples/micro_speech/recognize_commands.h \
+$(MICRO_FEATURES_GENERATOR_HDRS)
 
 # Find any platform-specific rules for this example.
 include $(wildcard tensorflow/lite/experimental/micro/examples/micro_speech/*/Makefile.inc)
 
+$(eval $(call microlite_test,micro_features_fft_test,\
+$(MICRO_FEATURES_FFT_TEST_SRCS),$(MICRO_FEATURES_FFT_TEST_HDRS)))
+
+$(eval $(call microlite_test,micro_features_filterbank_test,\
+$(MICRO_FEATURES_FILTERBANK_TEST_SRCS),$(MICRO_FEATURES_FILTERBANK_TEST_HDRS)))
+
+$(eval $(call microlite_test,micro_features_frontend_test,\
+$(MICRO_FEATURES_FRONTEND_TEST_SRCS),$(MICRO_FEATURES_FRONTEND_TEST_HDRS)))
+
+$(eval $(call microlite_test,micro_features_log_scale_test,\
+$(MICRO_FEATURES_LOG_SCALE_TEST_SRCS),$(MICRO_FEATURES_LOG_SCALE_TEST_HDRS)))
+
+$(eval $(call microlite_test,micro_features_noise_reduction_test,\
+$(MICRO_FEATURES_NOISE_REDUCTION_TEST_SRCS),$(MICRO_FEATURES_NOISE_REDUCTION_TEST_HDRS)))
+
+$(eval $(call microlite_test,micro_features_pcan_gain_control_test,\
+$(MICRO_FEATURES_PCAN_GAIN_CONTROL_TEST_SRCS),$(MICRO_FEATURES_PCAN_GAIN_CONTROL_TEST_HDRS)))
+
+$(eval $(call microlite_test,micro_features_window_test,\
+$(MICRO_FEATURES_WINDOW_TEST_SRCS),$(MICRO_FEATURES_WINDOW_TEST_HDRS)))
+
+# Test the code for feature generation.
+$(eval $(call microlite_test,micro_features_generator_test,\
+$(MICRO_FEATURES_GENERATOR_TEST_SRCS), $(MICRO_FEATURES_GENERATOR_TEST_HDRS)))
+
 # Tests loading and running a speech model.
 $(eval $(call microlite_test,micro_speech_test,\
 $(MICRO_SPEECH_TEST_SRCS),$(MICRO_SPEECH_TEST_HDRS)))
 
 # Test the code for feature generation.
-$(eval $(call microlite_test,preprocessor_test,\
+$(eval $(call microlite_test,simple_features_generator_test,\
-$(PREPROCESSOR_TEST_SRCS), $(PREPROCESSOR_TEST_HDRS)))
+$(SIMPLE_FEATURES_GENERATOR_TEST_SRCS), $(SIMPLE_FEATURES_GENERATOR_TEST_HDRS)))
 
 # Tests the audio provider module.
 $(eval $(call microlite_test,audio_provider_test,\
 $(AUDIO_PROVIDER_TEST_SRCS),$(AUDIO_PROVIDER_TEST_HDRS)))
 
+# Tests the audio provider mock module.
+$(eval $(call microlite_test,audio_provider_mock_test,\
+$(AUDIO_PROVIDER_MOCK_TEST_SRCS),$(AUDIO_PROVIDER_MOCK_TEST_HDRS)))
+
 # Tests the feature provider module.
 $(eval $(call microlite_test,feature_provider_test,\
 $(FEATURE_PROVIDER_TEST_SRCS),$(FEATURE_PROVIDER_TEST_HDRS)))
 
-# Tests the feature provider module.
+# Tests the feature provider module using the mock audio provider.
+$(eval $(call microlite_test,feature_provider_mock_test,\
+$(FEATURE_PROVIDER_MOCK_TEST_SRCS),$(FEATURE_PROVIDER_MOCK_TEST_HDRS)))
+
+# Tests the command recognizer module.
 $(eval $(call microlite_test,recognize_commands_test,\
 $(RECOGNIZE_COMMANDS_TEST_SRCS),$(RECOGNIZE_COMMANDS_TEST_HDRS)))
 
 # Builds a standalone speech command recognizer binary.
 $(eval $(call microlite_test,micro_speech,\
 $(MICRO_SPEECH_SRCS),$(MICRO_SPEECH_HDRS)))
+
+# Builds a standalone speech command recognizer binary using fake audio input.
+$(eval $(call microlite_test,micro_speech_mock,\
+$(MICRO_SPEECH_MOCK_SRCS),$(MICRO_SPEECH_MOCK_HDRS)))

tensorflow/lite/experimental/micro/examples/micro_speech/README.md

@@ -83,7 +83,8 @@ If you see a compiling error on older machines, try leaving out the `--copt` arg
 ```
 bazel run tensorflow/examples/speech_commands:freeze -- \
 --model_architecture=tiny_conv --window_stride=20 --preprocess=average \
---wanted_words="yes,no" --quantize=1 --output_file=/tmp/tiny_conv.pb
+--wanted_words="yes,no" --quantize=1 --output_file=/tmp/tiny_conv.pb \
+--start_checkpoint=/tmp/speech_commands_train/tiny_conv.ckpt-18000
 ```
 
 The next step is to create a TensorFlow Lite file from the frozen graph:
@@ -99,5 +100,5 @@ bazel run tensorflow/lite/toco:toco -- \
 Finally, convert the file into a C source file that can be compiled into an embedded system:
 
 ```
-xxd -i /tmp/tiny_conv.tflite > /tmp/tiny_conv_model_data.cc
+xxd -i /tmp/tiny_conv.tflite > /tmp/tiny_conv_simple_features_model_data.cc
 ```

tensorflow/lite/experimental/micro/examples/micro_speech/apollo3/Makefile.inc

@@ -5,7 +5,7 @@ ifeq ($(TARGET), apollo3evb)
     $(AP3_MICRO_DIR)/../preprocessor.cc \
     $(AP3_MICRO_DIR)/pushbutton_main.c \
     $(AP3_MICRO_DIR)/pushbutton_test.cc \
-    $(AP3_MICRO_DIR)/../tiny_conv_model_data.cc \
+    $(AP3_MICRO_DIR)/../simple_features/tiny_conv_simple_features_model_data.cc \
     $(APOLLO3_SDK)/devices/am_devices_led.c
   ALL_SRCS += $(PUSHBUTTON_MICRO_SPEECH_TEST_SRCS)
   PUSHBUTTON_MICRO_SPEECH_TEST_OBJS := $(addprefix $(OBJDIR), \
@@ -24,8 +24,8 @@ ifeq ($(TARGET), apollo3evb)
   PUSHBUTTON_CMSIS_SPEECH_TEST_SRCS := \
     $(AP3_MICRO_DIR)/pushbutton_main.c \
     $(AP3_MICRO_DIR)/pushbutton_test.cc \
-    $(AP3_MICRO_DIR)/../tiny_conv_model_data.cc \
+    $(AP3_MICRO_DIR)/../simple_features/tiny_conv_simple_features_model_data.cc \
-    $(CMSIS_DIR)/preprocessor.cc \
+    $(CMSIS_DIR)/simple_features_generator.cc \
     $(CMSIS_EXT_DIR)/arm_cmplx_mag_squared_q10p6.c \
     $(CMSIS_DIR)/hanning.c \
     $(APOLLO3_SDK)/devices/am_devices_led.c \

tensorflow/lite/experimental/micro/examples/micro_speech/apollo3/pushbutton_test.cc

@@ -17,8 +17,8 @@ limitations under the License.
  * micro_speech_test.cc */
 
 #include "tensorflow/lite/c/c_api_internal.h"
-#include "tensorflow/lite/experimental/micro/examples/micro_speech/preprocessor.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/simple_features_generator.h"
-#include "tensorflow/lite/experimental/micro/examples/micro_speech/tiny_conv_model_data.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/tiny_conv_simple_features_model_data.h"
 #include "tensorflow/lite/experimental/micro/kernels/all_ops_resolver.h"
 #include "tensorflow/lite/experimental/micro/micro_error_reporter.h"
 #include "tensorflow/lite/experimental/micro/micro_interpreter.h"
@@ -32,20 +32,36 @@ uint8_t g_unknown_score = 0;
 uint8_t g_yes_score = 0;
 uint8_t g_no_score = 0;
 
+namespace {
+
+TfLiteStatus GenerateSimpleFeatures_1sec(tflite::ErrorReporter* error_reporter,
+                                         const int16_t* input,
+                                         uint8_t* output) {
+  int i;
+  for (i = 0; i < 49; i++) {
+    GenerateSimpleFeatures(error_reporter, input + i * 320, 480, 43,
+                           output + i * 43);
+  }
+  return kTfLiteOk;
+}
+
+}  // namespace
+
 TF_LITE_MICRO_TESTS_BEGIN
 
-TF_LITE_MICRO_TEST(TestPreprocessor) {
+TF_LITE_MICRO_TEST(TestSimpleFeaturesGenerator) {
   tflite::MicroErrorReporter micro_error_reporter;
   tflite::ErrorReporter* error_reporter = &micro_error_reporter;
 
   uint8_t preprocessed_data[43 * 49];
-  TfLiteStatus preprocess_1sec_status =
+  TfLiteStatus generate_1sec_status = GenerateSimpleFeatures_1sec(
-      Preprocess_1sec(error_reporter, captured_data, preprocessed_data);
+      error_reporter, captured_data, preprocessed_data);
-  TF_LITE_MICRO_EXPECT_EQ(kTfLiteOk, preprocess_1sec_status);
+  TF_LITE_MICRO_EXPECT_EQ(kTfLiteOk, generate_1sec_status);
 
   // Map the model into a usable data structure. This doesn't involve any
   // copying or parsing, it's a very lightweight operation.
-  const tflite::Model* model = ::tflite::GetModel(g_tiny_conv_model_data);
+  const tflite::Model* model =
+      ::tflite::GetModel(g_tiny_conv_simple_features_model_data);
   if (model->version() != TFLITE_SCHEMA_VERSION) {
     error_reporter->Report(
         "Model provided is schema version %d not equal "

tensorflow/lite/experimental/micro/examples/micro_speech/audio_provider.cc

@@ -15,7 +15,7 @@ limitations under the License.
 
 #include "tensorflow/lite/experimental/micro/examples/micro_speech/audio_provider.h"
 
-#include "tensorflow/lite/experimental/micro/examples/micro_speech/model_settings.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/micro_model_settings.h"
 
 namespace {
 int16_t g_dummy_audio_data[kMaxAudioSampleSize];

tensorflow/lite/experimental/micro/examples/micro_speech/audio_provider_mock.cc

@@ -0,0 +1,57 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/audio_provider.h"
+
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/micro_model_settings.h"
+
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/no_1000ms_sample_data.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/yes_1000ms_sample_data.h"
+
+namespace {
+int16_t g_dummy_audio_data[kMaxAudioSampleSize];
+int32_t g_latest_audio_timestamp = 0;
+}  // namespace
+
+TfLiteStatus GetAudioSamples(tflite::ErrorReporter* error_reporter,
+                             int start_ms, int duration_ms,
+                             int* audio_samples_size, int16_t** audio_samples) {
+  const int yes_start = (0 * kAudioSampleFrequency) / 1000;
+  const int yes_end = (1000 * kAudioSampleFrequency) / 1000;
+  const int no_start = (4000 * kAudioSampleFrequency) / 1000;
+  const int no_end = (5000 * kAudioSampleFrequency) / 1000;
+  const int wraparound = (8000 * kAudioSampleFrequency) / 1000;
+  const int start_sample = (start_ms * kAudioSampleFrequency) / 1000;
+  for (int i = 0; i < kMaxAudioSampleSize; ++i) {
+    const int sample_index = (start_sample + i) % wraparound;
+    int16_t sample;
+    if ((sample_index >= yes_start) && (sample_index < yes_end)) {
+      sample = g_yes_1000ms_sample_data[sample_index - yes_start];
+    } else if ((sample_index >= no_start) && (sample_index < no_end)) {
+      sample = g_no_1000ms_sample_data[sample_index - no_start];
+    } else {
+      sample = 0;
+    }
+    g_dummy_audio_data[i] = sample;
+  }
+  *audio_samples_size = kMaxAudioSampleSize;
+  *audio_samples = g_dummy_audio_data;
+  return kTfLiteOk;
+}
+
+int32_t LatestAudioTimestamp() {
+  g_latest_audio_timestamp += 100;
+  return g_latest_audio_timestamp;
+}

tensorflow/lite/experimental/micro/examples/micro_speech/audio_provider_mock_test.cc

@@ -0,0 +1,76 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/audio_provider.h"
+
+#include <limits>
+
+#include "tensorflow/lite/c/c_api_internal.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/micro_model_settings.h"
+#include "tensorflow/lite/experimental/micro/micro_error_reporter.h"
+#include "tensorflow/lite/experimental/micro/testing/micro_test.h"
+
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/no_1000ms_sample_data.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/yes_1000ms_sample_data.h"
+
+TF_LITE_MICRO_TESTS_BEGIN
+
+TF_LITE_MICRO_TEST(TestAudioProviderMock) {
+  tflite::MicroErrorReporter micro_error_reporter;
+  tflite::ErrorReporter* error_reporter = &micro_error_reporter;
+
+  int audio_samples_size = 0;
+  int16_t* audio_samples = nullptr;
+  TfLiteStatus get_status =
+      GetAudioSamples(error_reporter, 0, kFeatureSliceDurationMs,
+                      &audio_samples_size, &audio_samples);
+  TF_LITE_MICRO_EXPECT_EQ(kTfLiteOk, get_status);
+  TF_LITE_MICRO_EXPECT_LE(audio_samples_size, kMaxAudioSampleSize);
+  TF_LITE_MICRO_EXPECT_NE(audio_samples, nullptr);
+  for (int i = 0; i < audio_samples_size; ++i) {
+    TF_LITE_MICRO_EXPECT_EQ(g_yes_1000ms_sample_data[i], audio_samples[i]);
+  }
+
+  get_status = GetAudioSamples(error_reporter, 500, kFeatureSliceDurationMs,
+                               &audio_samples_size, &audio_samples);
+  TF_LITE_MICRO_EXPECT_EQ(kTfLiteOk, get_status);
+  TF_LITE_MICRO_EXPECT_LE(audio_samples_size, kMaxAudioSampleSize);
+  TF_LITE_MICRO_EXPECT_NE(audio_samples, nullptr);
+  for (int i = 0; i < audio_samples_size; ++i) {
+    TF_LITE_MICRO_EXPECT_EQ(g_yes_1000ms_sample_data[i + 8000],
+                            audio_samples[i]);
+  }
+
+  get_status = GetAudioSamples(error_reporter, 1500, kFeatureSliceDurationMs,
+                               &audio_samples_size, &audio_samples);
+  TF_LITE_MICRO_EXPECT_EQ(kTfLiteOk, get_status);
+  TF_LITE_MICRO_EXPECT_LE(audio_samples_size, kMaxAudioSampleSize);
+  TF_LITE_MICRO_EXPECT_NE(audio_samples, nullptr);
+  for (int i = 0; i < audio_samples_size; ++i) {
+    TF_LITE_MICRO_EXPECT_EQ(0, audio_samples[i]);
+  }
+
+  get_status = GetAudioSamples(error_reporter, 12250, kFeatureSliceDurationMs,
+                               &audio_samples_size, &audio_samples);
+  TF_LITE_MICRO_EXPECT_EQ(kTfLiteOk, get_status);
+  TF_LITE_MICRO_EXPECT_LE(audio_samples_size, kMaxAudioSampleSize);
+  TF_LITE_MICRO_EXPECT_NE(audio_samples, nullptr);
+  for (int i = 0; i < audio_samples_size; ++i) {
+    TF_LITE_MICRO_EXPECT_EQ(g_no_1000ms_sample_data[i + 4000],
+                            audio_samples[i]);
+  }
+}
+
+TF_LITE_MICRO_TESTS_END

tensorflow/lite/experimental/micro/examples/micro_speech/audio_provider_test.cc

@@ -18,7 +18,7 @@ limitations under the License.
 #include <limits>
 
 #include "tensorflow/lite/c/c_api_internal.h"
-#include "tensorflow/lite/experimental/micro/examples/micro_speech/model_settings.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/micro_model_settings.h"
 #include "tensorflow/lite/experimental/micro/micro_error_reporter.h"
 #include "tensorflow/lite/experimental/micro/testing/micro_test.h"
 

tensorflow/lite/experimental/micro/examples/micro_speech/disco_f746ng/audio_provider.cc

@@ -15,7 +15,7 @@ limitations under the License.
 
 #include "tensorflow/lite/experimental/micro/examples/micro_speech/audio_provider.h"
 
-#include "tensorflow/lite/experimental/micro/examples/micro_speech/model_settings.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/micro_model_settings.h"
 
 #include "AUDIO_DISCO_F746NG.h"
 #include "SDRAM_DISCO_F746NG.h"

tensorflow/lite/experimental/micro/examples/micro_speech/feature_provider.cc

@@ -16,8 +16,8 @@ limitations under the License.
 #include "tensorflow/lite/experimental/micro/examples/micro_speech/feature_provider.h"
 
 #include "tensorflow/lite/experimental/micro/examples/micro_speech/audio_provider.h"
-#include "tensorflow/lite/experimental/micro/examples/micro_speech/model_settings.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/micro_features_generator.h"
-#include "tensorflow/lite/experimental/micro/examples/micro_speech/preprocessor.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/micro_model_settings.h"
 
 FeatureProvider::FeatureProvider(int feature_size, uint8_t* feature_data)
     : feature_size_(feature_size),
@@ -48,6 +48,10 @@ TfLiteStatus FeatureProvider::PopulateFeatureData(
   int slices_needed = current_step - last_step;
   // If this is the first call, make sure we don't use any cached information.
   if (is_first_run_) {
+    TfLiteStatus init_status = InitializeMicroFeatures(error_reporter);
+    if (init_status != kTfLiteOk) {
+      return init_status;
+    }
     is_first_run_ = false;
     slices_needed = kFeatureSliceCount;
   }
@@ -99,11 +103,12 @@ TfLiteStatus FeatureProvider::PopulateFeatureData(
         return kTfLiteError;
       }
       uint8_t* new_slice_data = feature_data_ + (new_slice * kFeatureSliceSize);
-      TfLiteStatus preprocess_status =
+      size_t num_samples_read;
-          Preprocess(error_reporter, audio_samples, audio_samples_size,
+      TfLiteStatus generate_status = GenerateMicroFeatures(
-                     kFeatureSliceSize, new_slice_data);
+          error_reporter, audio_samples, audio_samples_size, kFeatureSliceSize,
-      if (preprocess_status != kTfLiteOk) {
+          new_slice_data, &num_samples_read);
-        return preprocess_status;
+      if (generate_status != kTfLiteOk) {
+        return generate_status;
       }
     }
   }

tensorflow/lite/experimental/micro/examples/micro_speech/feature_provider_mock_test.cc

@@ -0,0 +1,66 @@
+/* Copyright 2019 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+
+#include "tensorflow/lite/c/c_api_internal.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/feature_provider.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/micro_model_settings.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/no_micro_features_data.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/yes_micro_features_data.h"
+#include "tensorflow/lite/experimental/micro/micro_error_reporter.h"
+#include "tensorflow/lite/experimental/micro/testing/micro_test.h"
+
+TF_LITE_MICRO_TESTS_BEGIN
+
+TF_LITE_MICRO_TEST(TestFeatureProviderMockYes) {
+  tflite::MicroErrorReporter micro_error_reporter;
+  tflite::ErrorReporter* error_reporter = &micro_error_reporter;
+
+  uint8_t feature_data[kFeatureElementCount];
+  FeatureProvider feature_provider(kFeatureElementCount, feature_data);
+
+  int how_many_new_slices = 0;
+  TfLiteStatus populate_status = feature_provider.PopulateFeatureData(
+      error_reporter, /* last_time_in_ms= */ 0, /* time_in_ms= */ 970,
+      &how_many_new_slices);
+  TF_LITE_MICRO_EXPECT_EQ(kTfLiteOk, populate_status);
+  TF_LITE_MICRO_EXPECT_EQ(kFeatureSliceCount, how_many_new_slices);
+
+  for (int i = 0; i < kFeatureElementCount; ++i) {
+    TF_LITE_MICRO_EXPECT_EQ(g_yes_micro_f2e59fea_nohash_1_data[i],
+                            feature_data[i]);
+  }
+}
+
+TF_LITE_MICRO_TEST(TestFeatureProviderMockNo) {
+  tflite::MicroErrorReporter micro_error_reporter;
+  tflite::ErrorReporter* error_reporter = &micro_error_reporter;
+
+  uint8_t feature_data[kFeatureElementCount];
+  FeatureProvider feature_provider(kFeatureElementCount, feature_data);
+
+  int how_many_new_slices = 0;
+  TfLiteStatus populate_status = feature_provider.PopulateFeatureData(
+      error_reporter, /* last_time_in_ms= */ 4000, /* time_in_ms= */ 4970,
+      &how_many_new_slices);
+  TF_LITE_MICRO_EXPECT_EQ(kTfLiteOk, populate_status);
+  TF_LITE_MICRO_EXPECT_EQ(kFeatureSliceCount, how_many_new_slices);
+
+  for (int i = 0; i < kFeatureElementCount; ++i) {
+    TF_LITE_MICRO_EXPECT_EQ(g_no_micro_f9643d42_nohash_4_data[i],
+                            feature_data[i]);
+  }
+}
+
+TF_LITE_MICRO_TESTS_END

tensorflow/lite/experimental/micro/examples/micro_speech/feature_provider_test.cc

@@ -15,7 +15,7 @@ limitations under the License.
 
 #include "tensorflow/lite/experimental/micro/examples/micro_speech/feature_provider.h"
 #include "tensorflow/lite/c/c_api_internal.h"
-#include "tensorflow/lite/experimental/micro/examples/micro_speech/model_settings.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/micro_model_settings.h"
 #include "tensorflow/lite/experimental/micro/micro_error_reporter.h"
 #include "tensorflow/lite/experimental/micro/testing/micro_test.h"
 

tensorflow/lite/experimental/micro/examples/micro_speech/main.cc

@@ -15,9 +15,9 @@ limitations under the License.
 
 #include "tensorflow/lite/experimental/micro/examples/micro_speech/audio_provider.h"
 #include "tensorflow/lite/experimental/micro/examples/micro_speech/feature_provider.h"
-#include "tensorflow/lite/experimental/micro/examples/micro_speech/model_settings.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/micro_model_settings.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/tiny_conv_micro_features_model_data.h"
 #include "tensorflow/lite/experimental/micro/examples/micro_speech/recognize_commands.h"
-#include "tensorflow/lite/experimental/micro/examples/micro_speech/tiny_conv_model_data.h"
 #include "tensorflow/lite/experimental/micro/kernels/all_ops_resolver.h"
 #include "tensorflow/lite/experimental/micro/micro_error_reporter.h"
 #include "tensorflow/lite/experimental/micro/micro_interpreter.h"
@@ -31,7 +31,8 @@ int main(int argc, char* argv[]) {
 
   // Map the model into a usable data structure. This doesn't involve any
   // copying or parsing, it's a very lightweight operation.
-  const tflite::Model* model = ::tflite::GetModel(g_tiny_conv_model_data);
+  const tflite::Model* model =
+      ::tflite::GetModel(g_tiny_conv_micro_features_model_data);
   if (model->version() != TFLITE_SCHEMA_VERSION) {
     error_reporter->Report(
         "Model provided is schema version %d not equal "
@@ -123,7 +124,8 @@ int main(int argc, char* argv[]) {
       return 1;
     }
     if (is_new_command) {
-      error_reporter->Report("Heard %s (%d)", found_command, score);
+      error_reporter->Report("Heard %s (%d) @%dms", found_command, score,
+                             current_time);
     }
   }
 

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/BUILD

@@ -0,0 +1,300 @@
+# Library for generating feature vectors from audio data
+
+package(
+    default_visibility = ["//visibility:public"],
+)
+
+licenses(["notice"])  # Apache 2.0
+
+load(
+    "//tensorflow/lite/experimental/micro/testing:micro_test.bzl",
+    "tflite_micro_cc_test",
+)
+
+cc_library(
+    name = "micro_model_settings",
+    srcs = [
+        "micro_model_settings.cc",
+    ],
+    hdrs = [
+        "micro_model_settings.h",
+    ],
+)
+
+cc_library(
+    name = "tiny_conv_micro_features_model_data",
+    srcs = [
+        "tiny_conv_micro_features_model_data.cc",
+    ],
+    hdrs = [
+        "tiny_conv_micro_features_model_data.h",
+    ],
+)
+
+cc_library(
+    name = "micro_features_test_data",
+    srcs = [
+        "no_micro_features_data.cc",
+        "yes_micro_features_data.cc",
+    ],
+    hdrs = [
+        "no_micro_features_data.h",
+        "yes_micro_features_data.h",
+    ],
+)
+
+cc_library(
+    name = "bits",
+    hdrs = ["bits.h"],
+)
+
+cc_library(
+    name = "static_alloc",
+    hdrs = ["static_alloc.h"],
+)
+
+cc_library(
+    name = "fft",
+    srcs = [
+        "fft.cc",
+        "fft_util.cc",
+    ],
+    hdrs = [
+        "fft.h",
+        "fft_util.h",
+    ],
+    deps = [
+        ":micro_model_settings",
+        ":static_alloc",
+        "//tensorflow/lite/c:c_api_internal",
+        "//tensorflow/lite/experimental/micro:micro_framework",
+        "@kissfft//:kiss_fftr_16",
+    ],
+)
+
+cc_library(
+    name = "filterbank",
+    srcs = [
+        "filterbank.cc",
+        "filterbank_util.cc",
+    ],
+    hdrs = [
+        "filterbank.h",
+        "filterbank_util.h",
+    ],
+    deps = [
+        ":bits",
+        ":fft",
+        ":micro_model_settings",
+        ":static_alloc",
+        "//tensorflow/lite/c:c_api_internal",
+        "//tensorflow/lite/experimental/micro:micro_framework",
+    ],
+)
+
+cc_library(
+    name = "frontend",
+    srcs = [
+        "frontend.cc",
+        "frontend_util.cc",
+    ],
+    hdrs = [
+        "frontend.h",
+        "frontend_util.h",
+    ],
+    deps = [
+        ":bits",
+        ":fft",
+        ":filterbank",
+        ":log_scale",
+        ":micro_model_settings",
+        ":noise_reduction",
+        ":pcan_gain_control",
+        ":window",
+        "//tensorflow/lite/c:c_api_internal",
+        "//tensorflow/lite/experimental/micro:micro_framework",
+    ],
+)
+
+cc_library(
+    name = "log_scale",
+    srcs = [
+        "log_lut.cc",
+        "log_scale.cc",
+        "log_scale_util.cc",
+    ],
+    hdrs = [
+        "log_lut.h",
+        "log_scale.h",
+        "log_scale_util.h",
+    ],
+    deps = [
+        ":bits",
+        ":micro_model_settings",
+        ":static_alloc",
+        "//tensorflow/lite/c:c_api_internal",
+        "//tensorflow/lite/experimental/micro:micro_framework",
+    ],
+)
+
+cc_library(
+    name = "noise_reduction",
+    srcs = [
+        "noise_reduction.cc",
+        "noise_reduction_util.cc",
+    ],
+    hdrs = [
+        "noise_reduction.h",
+        "noise_reduction_util.h",
+    ],
+    deps = [
+        ":micro_model_settings",
+        ":static_alloc",
+        "//tensorflow/lite/c:c_api_internal",
+        "//tensorflow/lite/experimental/micro:micro_framework",
+    ],
+)
+
+cc_library(
+    name = "pcan_gain_control",
+    srcs = [
+        "pcan_gain_control.cc",
+        "pcan_gain_control_util.cc",
+    ],
+    hdrs = [
+        "pcan_gain_control.h",
+        "pcan_gain_control_util.h",
+    ],
+    deps = [
+        ":bits",
+        ":micro_model_settings",
+        ":static_alloc",
+        "//tensorflow/lite/c:c_api_internal",
+        "//tensorflow/lite/experimental/micro:micro_framework",
+    ],
+)
+
+cc_library(
+    name = "window",
+    srcs = [
+        "window.cc",
+        "window_util.cc",
+    ],
+    hdrs = [
+        "window.h",
+        "window_util.h",
+    ],
+    deps = [
+        ":micro_model_settings",
+        ":static_alloc",
+        "//tensorflow/lite/c:c_api_internal",
+        "//tensorflow/lite/experimental/micro:micro_framework",
+    ],
+)
+
+cc_library(
+    name = "micro_features_generator",
+    srcs = [
+        "micro_features_generator.cc",
+    ],
+    hdrs = [
+        "micro_features_generator.h",
+    ],
+    deps = [
+        ":frontend",
+        ":micro_model_settings",
+        "//tensorflow/lite/c:c_api_internal",
+        "//tensorflow/lite/experimental/micro:micro_framework",
+    ],
+)
+
+cc_library(
+    name = "micro_features_generator_test_data",
+    srcs = [
+        "no_feature_data_slice.cc",
+        "yes_feature_data_slice.cc",
+    ],
+    hdrs = [
+        "no_feature_data_slice.h",
+        "yes_feature_data_slice.h",
+    ],
+)
+
+tflite_micro_cc_test(
+    name = "fft_test",
+    srcs = ["fft_test.cc"],
+    deps = [
+        ":fft",
+        "//tensorflow/lite/experimental/micro/testing:micro_test",
+    ],
+)
+
+tflite_micro_cc_test(
+    name = "filterbank_test",
+    srcs = ["filterbank_test.cc"],
+    deps = [
+        ":filterbank",
+        "//tensorflow/lite/experimental/micro/testing:micro_test",
+    ],
+)
+
+tflite_micro_cc_test(
+    name = "frontend_test",
+    srcs = ["frontend_test.cc"],
+    deps = [
+        ":frontend",
+        "//tensorflow/lite/experimental/micro/testing:micro_test",
+    ],
+)
+
+tflite_micro_cc_test(
+    name = "log_scale_test",
+    srcs = ["log_scale_test.cc"],
+    deps = [
+        ":log_scale",
+        "//tensorflow/lite/experimental/micro/testing:micro_test",
+    ],
+)
+
+tflite_micro_cc_test(
+    name = "noise_reduction_test",
+    srcs = ["noise_reduction_test.cc"],
+    deps = [
+        ":noise_reduction",
+        "//tensorflow/lite/experimental/micro/testing:micro_test",
+    ],
+)
+
+tflite_micro_cc_test(
+    name = "pcan_gain_control_test",
+    srcs = ["pcan_gain_control_test.cc"],
+    deps = [
+        ":pcan_gain_control",
+        "//tensorflow/lite/experimental/micro/testing:micro_test",
+    ],
+)
+
+tflite_micro_cc_test(
+    name = "window_test",
+    srcs = ["window_test.cc"],
+    deps = [
+        ":window",
+        "//tensorflow/lite/experimental/micro/testing:micro_test",
+    ],
+)
+
+tflite_micro_cc_test(
+    name = "micro_features_generator_test",
+    srcs = [
+        "micro_features_generator_test.cc",
+    ],
+    deps = [
+        ":micro_features_generator",
+        ":micro_features_generator_test_data",
+        ":micro_model_settings",
+        "//tensorflow/lite/c:c_api_internal",
+        "//tensorflow/lite/experimental/micro:micro_framework",
+        "//tensorflow/lite/experimental/micro/examples/micro_speech:audio_sample_test_data",
+        "//tensorflow/lite/experimental/micro/testing:micro_test",
+    ],
+)

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/bits.h

@@ -0,0 +1,94 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_BITS_H_
+#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_BITS_H_
+
+#include <cstdint>
+
+static inline int CountLeadingZeros32Slow(uint64_t n) {
+  int zeroes = 28;
+  if (n >> 16) zeroes -= 16, n >>= 16;
+  if (n >> 8) zeroes -= 8, n >>= 8;
+  if (n >> 4) zeroes -= 4, n >>= 4;
+  return "\4\3\2\2\1\1\1\1\0\0\0\0\0\0\0"[n] + zeroes;
+}
+
+static inline int CountLeadingZeros32(uint32_t n) {
+#if defined(_MSC_VER)
+  unsigned long result = 0;  // NOLINT(runtime/int)
+  if (_BitScanReverse(&result, n)) {
+    return 31 - result;
+  }
+  return 32;
+#elif defined(__GNUC__)
+
+  // Handle 0 as a special case because __builtin_clz(0) is undefined.
+  if (n == 0) {
+    return 32;
+  }
+  return __builtin_clz(n);
+#else
+  return CountLeadingZeros32Slow(n);
+#endif
+}
+
+static inline int MostSignificantBit32(uint32_t n) {
+  return 32 - CountLeadingZeros32(n);
+}
+
+static inline int CountLeadingZeros64Slow(uint64_t n) {
+  int zeroes = 60;
+  if (n >> 32) zeroes -= 32, n >>= 32;
+  if (n >> 16) zeroes -= 16, n >>= 16;
+  if (n >> 8) zeroes -= 8, n >>= 8;
+  if (n >> 4) zeroes -= 4, n >>= 4;
+  return "\4\3\2\2\1\1\1\1\0\0\0\0\0\0\0"[n] + zeroes;
+}
+
+static inline int CountLeadingZeros64(uint64_t n) {
+#if defined(_MSC_VER) && defined(_M_X64)
+  // MSVC does not have __buitin_clzll. Use _BitScanReverse64.
+  unsigned long result = 0;  // NOLINT(runtime/int)
+  if (_BitScanReverse64(&result, n)) {
+    return 63 - result;
+  }
+  return 64;
+#elif defined(_MSC_VER)
+  // MSVC does not have __buitin_clzll. Compose two calls to _BitScanReverse
+  unsigned long result = 0;  // NOLINT(runtime/int)
+  if ((n >> 32) && _BitScanReverse(&result, n >> 32)) {
+    return 31 - result;
+  }
+  if (_BitScanReverse(&result, n)) {
+    return 63 - result;
+  }
+  return 64;
+#elif defined(__GNUC__)
+
+  // Handle 0 as a special case because __builtin_clzll(0) is undefined.
+  if (n == 0) {
+    return 64;
+  }
+  return __builtin_clzll(n);
+#else
+  return CountLeadingZeros64Slow(n);
+#endif
+}
+
+static inline int MostSignificantBit64(uint64_t n) {
+  return 64 - CountLeadingZeros64(n);
+}
+
+#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_BITS_H_

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/fft.cc

@@ -0,0 +1,54 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/fft.h"
+
+#include <string.h>
+
+#define FIXED_POINT 16
+#include "kiss_fft.h"
+// Internal test dependency placeholder1
+// Internal test dependency placeholder2
+#include "tools/kiss_fftr.h"
+// Internal test dependency placeholder3
+
+void FftCompute(struct FftState* state, const int16_t* input,
+                int input_scale_shift) {
+  const size_t input_size = state->input_size;
+  const size_t fft_size = state->fft_size;
+
+  int16_t* fft_input = state->input;
+  // First, scale the input by the given shift.
+  int i;
+  for (i = 0; i < input_size; ++i) {
+    *fft_input++ = (*input++) << input_scale_shift;
+  }
+  // Zero out whatever else remains in the top part of the input.
+  for (; i < fft_size; ++i) {
+    *fft_input++ = 0;
+  }
+
+  // Apply the FFT.
+  kiss_fftr(reinterpret_cast<const kiss_fftr_cfg>(state->scratch), state->input,
+            reinterpret_cast<kiss_fft_cpx*>(state->output));
+}
+
+void FftInit(struct FftState* state) {
+  // All the initialization is done in FftPopulateState()
+}
+
+void FftReset(struct FftState* state) {
+  memset(state->input, 0, state->fft_size * sizeof(*state->input));
+  memset(state->output, 0, (state->fft_size / 2 + 1) * sizeof(*state->output));
+}

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/fft.h

@@ -0,0 +1,48 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_FFT_H_
+#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_FFT_H_
+
+#include <stdint.h>
+#include <stdlib.h>
+
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/micro_model_settings.h"
+
+struct complex_int16_t {
+  int16_t real;
+  int16_t imag;
+};
+
+struct FftState {
+  int16_t input[kMaxAudioSampleSize];
+  struct complex_int16_t output[kMaxAudioSampleSize + 2];
+  size_t fft_size;
+  size_t input_size;
+  // This magic number was derived from KissFFT's estimate of how much space it
+  // will need to process the particular lengths and datatypes we need to for
+  // these model settings. This size will need to be recalculated for different
+  // models, but you will see a runtime error if it's not large enough.
+  char scratch[2848];
+  size_t scratch_size;
+};
+
+void FftCompute(struct FftState* state, const int16_t* input,
+                int input_scale_shift);
+
+void FftInit(struct FftState* state);
+
+void FftReset(struct FftState* state);
+
+#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_FFT_H_

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/fft_test.cc

@@ -0,0 +1,55 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/fft.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/fft_util.h"
+
+#include "tensorflow/lite/experimental/micro/testing/micro_test.h"
+
+namespace {
+
+const int16_t kFakeWindow[] = {
+    0, 1151,   0, -5944, 0, 13311,  0, -21448, 0, 28327, 0, -32256, 0, 32255,
+    0, -28328, 0, 21447, 0, -13312, 0, 5943,   0, -1152, 0};
+const int kScaleShift = 0;
+
+}  // namespace
+
+TF_LITE_MICRO_TESTS_BEGIN
+
+TF_LITE_MICRO_TEST(FftTest_CheckOutputValues) {
+  tflite::MicroErrorReporter micro_error_reporter;
+  tflite::ErrorReporter* error_reporter = &micro_error_reporter;
+
+  struct FftState state;
+  TF_LITE_MICRO_EXPECT(FftPopulateState(
+      error_reporter, &state, sizeof(kFakeWindow) / sizeof(kFakeWindow[0])));
+
+  FftInit(&state);
+  FftCompute(&state, kFakeWindow, kScaleShift);
+
+  const struct complex_int16_t expected[] = {
+      {0, 0},    {-10, 9},     {-20, 0},   {-9, -10},     {0, 25},  {-119, 119},
+      {-887, 0}, {3000, 3000}, {0, -6401}, {-3000, 3000}, {886, 0}, {118, 119},
+      {0, 25},   {9, -10},     {19, 0},    {9, 9},        {0, 0}};
+  TF_LITE_MICRO_EXPECT_EQ(state.fft_size / 2 + 1,
+                          sizeof(expected) / sizeof(expected[0]));
+  int i;
+  for (i = 0; i <= state.fft_size / 2; ++i) {
+    TF_LITE_MICRO_EXPECT_NEAR(state.output[i].real, expected[i].real, 2);
+    TF_LITE_MICRO_EXPECT_NEAR(state.output[i].imag, expected[i].imag, 2);
+  }
+}
+
+TF_LITE_MICRO_TESTS_END

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/fft_util.cc

@@ -0,0 +1,54 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/fft_util.h"
+
+#define FIXED_POINT 16
+#include "kiss_fft.h"
+#include "tools/kiss_fftr.h"
+
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/static_alloc.h"
+
+int FftPopulateState(tflite::ErrorReporter* error_reporter,
+                     struct FftState* state, size_t input_size) {
+  state->input_size = input_size;
+  state->fft_size = 1;
+  while (state->fft_size < state->input_size) {
+    state->fft_size <<= 1;
+  }
+
+  STATIC_ALLOC_ENSURE_ARRAY_SIZE(state->input,
+                                 (state->fft_size * sizeof(*state->input)));
+
+  STATIC_ALLOC_ENSURE_ARRAY_SIZE(
+      state->output, ((state->fft_size / 2 + 1) * sizeof(*state->output) * 2));
+
+  // Ask kissfft how much memory it wants.
+  size_t scratch_size = 0;
+  kiss_fftr_cfg kfft_cfg =
+      kiss_fftr_alloc(state->fft_size, 0, nullptr, &scratch_size);
+  if (kfft_cfg != nullptr) {
+    error_reporter->Report("Kiss memory sizing failed.");
+    return 0;
+  }
+  STATIC_ALLOC_ENSURE_ARRAY_SIZE(state->scratch, scratch_size);
+  state->scratch_size = scratch_size;
+  // Let kissfft configure the scratch space we just allocated
+  kfft_cfg = kiss_fftr_alloc(state->fft_size, 0, state->scratch, &scratch_size);
+  if (reinterpret_cast<char*>(kfft_cfg) != state->scratch) {
+    error_reporter->Report("Kiss memory preallocation strategy failed.");
+    return 0;
+  }
+  return 1;
+}

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/fft_util.h

@@ -0,0 +1,26 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_FFT_UTIL_H_
+#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_FFT_UTIL_H_
+
+#include "tensorflow/lite/c/c_api_internal.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/fft.h"
+#include "tensorflow/lite/experimental/micro/micro_error_reporter.h"
+
+// Prepares and FFT for the given input size.
+int FftPopulateState(tflite::ErrorReporter* error_reporter,
+                     struct FftState* state, size_t input_size);
+
+#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_FFT_UTIL_H_

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/filterbank.cc

@@ -0,0 +1,135 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/filterbank.h"
+
+#include <string.h>
+
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/bits.h"
+
+void FilterbankConvertFftComplexToEnergy(struct FilterbankState* state,
+                                         struct complex_int16_t* fft_output,
+                                         int32_t* energy) {
+  const int end_index = state->end_index;
+  int i;
+  energy += state->start_index;
+  fft_output += state->start_index;
+  for (i = state->start_index; i < end_index; ++i) {
+    const int32_t real = fft_output->real;
+    const int32_t imag = fft_output->imag;
+    fft_output++;
+    const uint32_t mag_squared = (real * real) + (imag * imag);
+    *energy++ = mag_squared;
+  }
+}
+
+void FilterbankAccumulateChannels(struct FilterbankState* state,
+                                  const int32_t* energy) {
+  uint64_t* work = state->work;
+  uint64_t weight_accumulator = 0;
+  uint64_t unweight_accumulator = 0;
+
+  const int16_t* channel_frequency_starts = state->channel_frequency_starts;
+  const int16_t* channel_weight_starts = state->channel_weight_starts;
+  const int16_t* channel_widths = state->channel_widths;
+
+  int num_channels_plus_1 = state->num_channels + 1;
+  int i;
+  for (i = 0; i < num_channels_plus_1; ++i) {
+    const int32_t* magnitudes = energy + *channel_frequency_starts++;
+    const int16_t* weights = state->weights + *channel_weight_starts;
+    const int16_t* unweights = state->unweights + *channel_weight_starts++;
+    const int width = *channel_widths++;
+    int j;
+    for (j = 0; j < width; ++j) {
+      weight_accumulator += *weights++ * (static_cast<uint64_t>(*magnitudes));
+      unweight_accumulator +=
+          *unweights++ * (static_cast<uint64_t>(*magnitudes));
+      ++magnitudes;
+    }
+    *work++ = weight_accumulator;
+    weight_accumulator = unweight_accumulator;
+    unweight_accumulator = 0;
+  }
+}
+
+static uint16_t Sqrt32(uint32_t num) {
+  if (num == 0) {
+    return 0;
+  }
+  uint32_t res = 0;
+  int max_bit_number = 32 - MostSignificantBit32(num);
+  max_bit_number |= 1;
+  uint32_t bit = 1U << (31 - max_bit_number);
+  int iterations = (31 - max_bit_number) / 2 + 1;
+  while (iterations--) {
+    if (num >= res + bit) {
+      num -= res + bit;
+      res = (res >> 1U) + bit;
+    } else {
+      res >>= 1U;
+    }
+    bit >>= 2U;
+  }
+  // Do rounding - if we have the bits.
+  if (num > res && res != 0xFFFF) {
+    ++res;
+  }
+  return res;
+}
+
+static uint32_t Sqrt64(uint64_t num) {
+  // Take a shortcut and just use 32 bit operations if the upper word is all
+  // clear. This will cause a slight off by one issue for numbers close to 2^32,
+  // but it probably isn't going to matter (and gives us a big performance win).
+  if ((num >> 32) == 0) {
+    return Sqrt32(static_cast<uint32_t>(num));
+  }
+  uint64_t res = 0;
+  int max_bit_number = 64 - MostSignificantBit64(num);
+  max_bit_number |= 1;
+  uint64_t bit = 1ULL << (63 - max_bit_number);
+  int iterations = (63 - max_bit_number) / 2 + 1;
+  while (iterations--) {
+    if (num >= res + bit) {
+      num -= res + bit;
+      res = (res >> 1U) + bit;
+    } else {
+      res >>= 1U;
+    }
+    bit >>= 2U;
+  }
+  // Do rounding - if we have the bits.
+  if (num > res && res != 0xFFFFFFFFLL) {
+    ++res;
+  }
+  return res;
+}
+
+uint32_t* FilterbankSqrt(struct FilterbankState* state, int scale_down_shift) {
+  const int num_channels = state->num_channels;
+  const int64_t* work = reinterpret_cast<int64_t*>(state->work + 1);
+  // Reuse the work buffer since we're fine clobbering it at this point to hold
+  // the output.
+  uint32_t* output = reinterpret_cast<uint32_t*>(state->work);
+  int i;
+  for (i = 0; i < num_channels; ++i) {
+    *output++ = Sqrt64(*work++) >> scale_down_shift;
+  }
+  return reinterpret_cast<uint32_t*>(state->work);
+}
+
+void FilterbankReset(struct FilterbankState* state) {
+  memset(state->work, 0, (state->num_channels + 1) * sizeof(*state->work));
+}

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/filterbank.h

@@ -0,0 +1,56 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_FILTERBANK_H_
+#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_FILTERBANK_H_
+
+#include <stdint.h>
+#include <stdlib.h>
+
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/fft.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/micro_model_settings.h"
+
+#define kFilterbankBits 12
+
+struct FilterbankState {
+  int num_channels;
+  int start_index;
+  int end_index;
+  int16_t channel_frequency_starts[kFeatureSliceSize + 1];
+  int16_t channel_weight_starts[kFeatureSliceSize + 1];
+  int16_t channel_widths[kFeatureSliceSize + 1];
+  int16_t weights[316];
+  int16_t unweights[316];
+  uint64_t work[kFeatureSliceSize + 1];
+};
+
+// Converts the relevant complex values of an FFT output into energy (the
+// square magnitude).
+void FilterbankConvertFftComplexToEnergy(struct FilterbankState* state,
+                                         struct complex_int16_t* fft_output,
+                                         int32_t* energy);
+
+// Computes the mel-scale filterbank on the given energy array. Output is cached
+// internally - to fetch it, you need to call FilterbankSqrt.
+void FilterbankAccumulateChannels(struct FilterbankState* state,
+                                  const int32_t* energy);
+
+// Applies an integer square root to the 64 bit intermediate values of the
+// filterbank, and returns a pointer to them. Memory will be invalidated the
+// next time FilterbankAccumulateChannels is called.
+uint32_t* FilterbankSqrt(struct FilterbankState* state, int scale_down_shift);
+
+void FilterbankReset(struct FilterbankState* state);
+
+#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_FILTERBANK_H_

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/filterbank_test.cc

@@ -0,0 +1,228 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/filterbank.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/filterbank_util.h"
+
+#include <cstring>
+
+#include "tensorflow/lite/experimental/micro/testing/micro_test.h"
+
+namespace {
+
+const int kSampleRate = 1000;
+const int kSpectrumSize = 17;
+const int kStartIndex = 1;
+const int kEndIndex = 15;
+const int32_t kEnergy[] = {-1,     181,      400,      181,      625,    28322,
+                           786769, 18000000, 40972801, 18000000, 784996, 28085,
+                           625,    181,      361,      -1,       -1};
+const uint64_t kWork[] = {1835887, 61162970173, 258694800000};
+const int kScaleShift = 0;
+
+// Test filterbank generation using scaled-down defaults.
+class FilterbankTestConfig {
+ public:
+  FilterbankTestConfig() {
+    config_.num_channels = 2;
+    config_.lower_band_limit = 8.0;
+    config_.upper_band_limit = 450.0;
+  }
+
+  struct FilterbankConfig config_;
+};
+
+}  // namespace
+
+TF_LITE_MICRO_TESTS_BEGIN
+
+TF_LITE_MICRO_TEST(FilterbankTest_CheckStartIndex) {
+  tflite::MicroErrorReporter micro_error_reporter;
+  tflite::ErrorReporter* error_reporter = &micro_error_reporter;
+
+  FilterbankTestConfig config;
+  struct FilterbankState state;
+  TF_LITE_MICRO_EXPECT(FilterbankPopulateState(
+      error_reporter, &config.config_, &state, kSampleRate, kSpectrumSize));
+
+  TF_LITE_MICRO_EXPECT_EQ(state.start_index, kStartIndex);
+}
+
+TF_LITE_MICRO_TEST(FilterbankTest_CheckEndIndex) {
+  tflite::MicroErrorReporter micro_error_reporter;
+  tflite::ErrorReporter* error_reporter = &micro_error_reporter;
+
+  FilterbankTestConfig config;
+  struct FilterbankState state;
+  TF_LITE_MICRO_EXPECT(FilterbankPopulateState(
+      error_reporter, &config.config_, &state, kSampleRate, kSpectrumSize));
+
+  TF_LITE_MICRO_EXPECT_EQ(state.end_index, kEndIndex);
+}
+
+TF_LITE_MICRO_TEST(FilterbankTest_CheckChannelFrequencyStarts) {
+  tflite::MicroErrorReporter micro_error_reporter;
+  tflite::ErrorReporter* error_reporter = &micro_error_reporter;
+
+  FilterbankTestConfig config;
+  struct FilterbankState state;
+  TF_LITE_MICRO_EXPECT(FilterbankPopulateState(
+      error_reporter, &config.config_, &state, kSampleRate, kSpectrumSize));
+
+  const int16_t expected[] = {0, 4, 8};
+  TF_LITE_MICRO_EXPECT_EQ(state.num_channels + 1,
+                          sizeof(expected) / sizeof(expected[0]));
+  int i;
+  for (i = 0; i <= state.num_channels; ++i) {
+    TF_LITE_MICRO_EXPECT_EQ(state.channel_frequency_starts[i], expected[i]);
+  }
+}
+
+TF_LITE_MICRO_TEST(FilterbankTest_CheckChannelWeightStarts) {
+  tflite::MicroErrorReporter micro_error_reporter;
+  tflite::ErrorReporter* error_reporter = &micro_error_reporter;
+
+  FilterbankTestConfig config;
+  struct FilterbankState state;
+  TF_LITE_MICRO_EXPECT(FilterbankPopulateState(
+      error_reporter, &config.config_, &state, kSampleRate, kSpectrumSize));
+
+  const int16_t expected[] = {0, 8, 16};
+  TF_LITE_MICRO_EXPECT_EQ(state.num_channels + 1,
+                          sizeof(expected) / sizeof(expected[0]));
+  int i;
+  for (i = 0; i <= state.num_channels; ++i) {
+    TF_LITE_MICRO_EXPECT_EQ(state.channel_weight_starts[i], expected[i]);
+  }
+}
+
+TF_LITE_MICRO_TEST(FilterbankTest_CheckChannelWidths) {
+  tflite::MicroErrorReporter micro_error_reporter;
+  tflite::ErrorReporter* error_reporter = &micro_error_reporter;
+
+  FilterbankTestConfig config;
+  struct FilterbankState state;
+  TF_LITE_MICRO_EXPECT(FilterbankPopulateState(
+      error_reporter, &config.config_, &state, kSampleRate, kSpectrumSize));
+
+  const int16_t expected[] = {8, 8, 8};
+  TF_LITE_MICRO_EXPECT_EQ(state.num_channels + 1,
+                          sizeof(expected) / sizeof(expected[0]));
+  int i;
+  for (i = 0; i <= state.num_channels; ++i) {
+    TF_LITE_MICRO_EXPECT_EQ(state.channel_widths[i], expected[i]);
+  }
+}
+
+TF_LITE_MICRO_TEST(FilterbankTest_CheckWeights) {
+  tflite::MicroErrorReporter micro_error_reporter;
+  tflite::ErrorReporter* error_reporter = &micro_error_reporter;
+
+  FilterbankTestConfig config;
+  struct FilterbankState state;
+  TF_LITE_MICRO_EXPECT(FilterbankPopulateState(
+      error_reporter, &config.config_, &state, kSampleRate, kSpectrumSize));
+
+  const int16_t expected[] = {0, 3277, 2217, 1200, 222,  0,   0,   0,
+                              0, 3376, 2468, 1591, 744,  0,   0,   0,
+                              0, 4020, 3226, 2456, 1708, 983, 277, 0};
+  TF_LITE_MICRO_EXPECT_EQ(state.channel_weight_starts[state.num_channels] +
+                              state.channel_widths[state.num_channels],
+                          sizeof(expected) / sizeof(expected[0]));
+  int i;
+  for (i = 0; i < sizeof(expected) / sizeof(expected[0]); ++i) {
+    TF_LITE_MICRO_EXPECT_EQ(state.weights[i], expected[i]);
+  }
+}
+
+TF_LITE_MICRO_TEST(FilterbankTest_CheckUnweights) {
+  tflite::MicroErrorReporter micro_error_reporter;
+  tflite::ErrorReporter* error_reporter = &micro_error_reporter;
+
+  FilterbankTestConfig config;
+  struct FilterbankState state;
+  TF_LITE_MICRO_EXPECT(FilterbankPopulateState(
+      error_reporter, &config.config_, &state, kSampleRate, kSpectrumSize));
+
+  const int16_t expected[] = {0, 819, 1879, 2896, 3874, 0,    0,    0,
+                              0, 720, 1628, 2505, 3352, 0,    0,    0,
+                              0, 76,  870,  1640, 2388, 3113, 3819, 0};
+  TF_LITE_MICRO_EXPECT_EQ(state.channel_weight_starts[state.num_channels] +
+                              state.channel_widths[state.num_channels],
+                          sizeof(expected) / sizeof(expected[0]));
+  int i;
+  for (i = 0; i < sizeof(expected) / sizeof(expected[0]); ++i) {
+    TF_LITE_MICRO_EXPECT_EQ(state.unweights[i], expected[i]);
+  }
+}
+
+TF_LITE_MICRO_TEST(FilterbankTest_CheckConvertFftComplexToEnergy) {
+  struct FilterbankState state;
+  state.start_index = kStartIndex;
+  state.end_index = kEndIndex;
+
+  struct complex_int16_t fake_fft[] = {
+      {0, 0},    {-10, 9},     {-20, 0},   {-9, -10},     {0, 25},  {-119, 119},
+      {-887, 0}, {3000, 3000}, {0, -6401}, {-3000, 3000}, {886, 0}, {118, 119},
+      {0, 25},   {9, -10},     {19, 0},    {9, 9},        {0, 0}};
+  int32_t* energy = reinterpret_cast<int32_t*>(fake_fft);
+  FilterbankConvertFftComplexToEnergy(&state, fake_fft, energy);
+
+  int i;
+  for (i = state.start_index; i < state.end_index; ++i) {
+    TF_LITE_MICRO_EXPECT_EQ(energy[i], kEnergy[i]);
+  }
+}
+
+TF_LITE_MICRO_TEST(FilterbankTest_CheckAccumulateChannels) {
+  tflite::MicroErrorReporter micro_error_reporter;
+  tflite::ErrorReporter* error_reporter = &micro_error_reporter;
+
+  FilterbankTestConfig config;
+  struct FilterbankState state;
+  TF_LITE_MICRO_EXPECT(FilterbankPopulateState(
+      error_reporter, &config.config_, &state, kSampleRate, kSpectrumSize));
+
+  FilterbankAccumulateChannels(&state, kEnergy);
+
+  TF_LITE_MICRO_EXPECT_EQ(state.num_channels + 1,
+                          sizeof(kWork) / sizeof(kWork[0]));
+  int i;
+  for (i = 0; i <= state.num_channels; ++i) {
+    TF_LITE_MICRO_EXPECT_EQ(state.work[i], kWork[i]);
+  }
+}
+
+TF_LITE_MICRO_TEST(FilterbankTest_CheckSqrt) {
+  tflite::MicroErrorReporter micro_error_reporter;
+  tflite::ErrorReporter* error_reporter = &micro_error_reporter;
+
+  FilterbankTestConfig config;
+  struct FilterbankState state;
+  TF_LITE_MICRO_EXPECT(FilterbankPopulateState(
+      error_reporter, &config.config_, &state, kSampleRate, kSpectrumSize));
+  std::memcpy(state.work, kWork, sizeof(kWork));
+
+  uint32_t* scaled_filterbank = FilterbankSqrt(&state, kScaleShift);
+
+  const uint32_t expected[] = {247311, 508620};
+  TF_LITE_MICRO_EXPECT_EQ(state.num_channels,
+                          sizeof(expected) / sizeof(expected[0]));
+  int i;
+  for (i = 0; i < state.num_channels; ++i) {
+    TF_LITE_MICRO_EXPECT_EQ(scaled_filterbank[i], expected[i]);
+  }
+}
+
+TF_LITE_MICRO_TESTS_END

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/filterbank_util.cc

@@ -0,0 +1,212 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/filterbank_util.h"
+
+#include <assert.h>
+#include <math.h>
+
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/static_alloc.h"
+
+#define kFilterbankIndexAlignment 4
+#define kFilterbankChannelBlockSize 4
+
+void FilterbankFillConfigWithDefaults(struct FilterbankConfig* config) {
+  config->num_channels = 32;
+  config->lower_band_limit = 125.0f;
+  config->upper_band_limit = 7500.0f;
+  config->output_scale_shift = 7;
+}
+
+static float FreqToMel(float freq) {
+  return 1127.0 * log(1.0 + (freq / 700.0));
+}
+
+static void CalculateCenterFrequencies(const int num_channels,
+                                       const float lower_frequency_limit,
+                                       const float upper_frequency_limit,
+                                       float* center_frequencies) {
+  assert(lower_frequency_limit >= 0.0f);
+  assert(upper_frequency_limit > lower_frequency_limit);
+
+  const float mel_low = FreqToMel(lower_frequency_limit);
+  const float mel_hi = FreqToMel(upper_frequency_limit);
+  const float mel_span = mel_hi - mel_low;
+  const float mel_spacing = mel_span / (static_cast<float>(num_channels));
+  int i;
+  for (i = 0; i < num_channels; ++i) {
+    center_frequencies[i] = mel_low + (mel_spacing * (i + 1));
+  }
+}
+
+static void QuantizeFilterbankWeights(const float float_weight, int16_t* weight,
+                                      int16_t* unweight) {
+  *weight = floor(float_weight * (1 << kFilterbankBits) + 0.5);
+  *unweight = floor((1.0 - float_weight) * (1 << kFilterbankBits) + 0.5);
+}
+
+int FilterbankPopulateState(tflite::ErrorReporter* error_reporter,
+                            const struct FilterbankConfig* config,
+                            struct FilterbankState* state, int sample_rate,
+                            int spectrum_size) {
+  state->num_channels = config->num_channels;
+  const int num_channels_plus_1 = config->num_channels + 1;
+
+  // How should we align things to index counts given the byte alignment?
+  const int index_alignment =
+      (kFilterbankIndexAlignment < sizeof(int16_t)
+           ? 1
+           : kFilterbankIndexAlignment / sizeof(int16_t));
+
+  STATIC_ALLOC_ENSURE_ARRAY_SIZE(
+      state->channel_frequency_starts,
+      (num_channels_plus_1 * sizeof(*state->channel_frequency_starts)));
+  STATIC_ALLOC_ENSURE_ARRAY_SIZE(
+      state->channel_weight_starts,
+      (num_channels_plus_1 * sizeof(*state->channel_weight_starts)));
+  STATIC_ALLOC_ENSURE_ARRAY_SIZE(
+      state->channel_widths,
+      (num_channels_plus_1 * sizeof(*state->channel_widths)));
+  STATIC_ALLOC_ENSURE_ARRAY_SIZE(state->work,
+                                 (num_channels_plus_1 * sizeof(*state->work)));
+
+  float center_mel_freqs[kFeatureSliceSize + 1];
+  STATIC_ALLOC_ENSURE_ARRAY_SIZE(
+      center_mel_freqs, (num_channels_plus_1 * sizeof(*center_mel_freqs)));
+
+  int16_t actual_channel_starts[kFeatureSliceSize + 1];
+  STATIC_ALLOC_ENSURE_ARRAY_SIZE(
+      actual_channel_starts,
+      (num_channels_plus_1 * sizeof(*actual_channel_starts)));
+
+  int16_t actual_channel_widths[kFeatureSliceSize + 1];
+  STATIC_ALLOC_ENSURE_ARRAY_SIZE(
+      actual_channel_widths,
+      (num_channels_plus_1 * sizeof(*actual_channel_widths)));
+
+  CalculateCenterFrequencies(num_channels_plus_1, config->lower_band_limit,
+                             config->upper_band_limit, center_mel_freqs);
+
+  // Always exclude DC.
+  const float hz_per_sbin =
+      0.5 * sample_rate / (static_cast<float>(spectrum_size) - 1);
+  state->start_index = 1.5 + config->lower_band_limit / hz_per_sbin;
+  state->end_index = 0;  // Initialized to zero here, but actually set below.
+
+  // For each channel, we need to figure out what frequencies belong to it, and
+  // how much padding we need to add so that we can efficiently multiply the
+  // weights and unweights for accumulation. To simplify the multiplication
+  // logic, all channels will have some multiplication to do (even if there are
+  // no frequencies that accumulate to that channel) - they will be directed to
+  // a set of zero weights.
+  int chan_freq_index_start = state->start_index;
+  int weight_index_start = 0;
+  int needs_zeros = 0;
+
+  int chan;
+  for (chan = 0; chan < num_channels_plus_1; ++chan) {
+    // Keep jumping frequencies until we overshoot the bound on this channel.
+    int freq_index = chan_freq_index_start;
+    while (FreqToMel((freq_index)*hz_per_sbin) <= center_mel_freqs[chan]) {
+      ++freq_index;
+    }
+
+    const int width = freq_index - chan_freq_index_start;
+    actual_channel_starts[chan] = chan_freq_index_start;
+    actual_channel_widths[chan] = width;
+
+    if (width == 0) {
+      // This channel doesn't actually get anything from the frequencies, it's
+      // always zero. We need then to insert some 'zero' weights into the
+      // output, and just redirect this channel to do a single multiplication at
+      // this point. For simplicity, the zeros are placed at the beginning of
+      // the weights arrays, so we have to go and update all the other
+      // weight_starts to reflect this shift (but only once).
+      state->channel_frequency_starts[chan] = 0;
+      state->channel_weight_starts[chan] = 0;
+      state->channel_widths[chan] = kFilterbankChannelBlockSize;
+      if (!needs_zeros) {
+        needs_zeros = 1;
+        int j;
+        for (j = 0; j < chan; ++j) {
+          state->channel_weight_starts[j] += kFilterbankChannelBlockSize;
+        }
+        weight_index_start += kFilterbankChannelBlockSize;
+      }
+    } else {
+      // How far back do we need to go to ensure that we have the proper
+      // alignment?
+      const int aligned_start =
+          (chan_freq_index_start / index_alignment) * index_alignment;
+      const int aligned_width = (chan_freq_index_start - aligned_start + width);
+      const int padded_width =
+          (((aligned_width - 1) / kFilterbankChannelBlockSize) + 1) *
+          kFilterbankChannelBlockSize;
+
+      state->channel_frequency_starts[chan] = aligned_start;
+      state->channel_weight_starts[chan] = weight_index_start;
+      state->channel_widths[chan] = padded_width;
+      weight_index_start += padded_width;
+    }
+    chan_freq_index_start = freq_index;
+  }
+
+  // Allocate the two arrays to store the weights - weight_index_start contains
+  // the index of what would be the next set of weights that we would need to
+  // add, so that's how many weights we need to allocate.
+  STATIC_ALLOC_ENSURE_ARRAY_SIZE(
+      state->weights, (weight_index_start * sizeof(*state->weights)));
+  for (int i = 0; i < weight_index_start; ++i) {
+    state->weights[i] = 0;
+  }
+  STATIC_ALLOC_ENSURE_ARRAY_SIZE(
+      state->unweights, (weight_index_start * sizeof(*state->unweights)));
+  for (int i = 0; i < weight_index_start; ++i) {
+    state->unweights[i] = 0;
+  }
+
+  // Next pass, compute all the weights. Since everything has been memset to
+  // zero, we only need to fill in the weights that correspond to some frequency
+  // for a channel.
+  const float mel_low = FreqToMel(config->lower_band_limit);
+  for (chan = 0; chan < num_channels_plus_1; ++chan) {
+    int frequency = actual_channel_starts[chan];
+    const int num_frequencies = actual_channel_widths[chan];
+    const int frequency_offset =
+        frequency - state->channel_frequency_starts[chan];
+    const int weight_start = state->channel_weight_starts[chan];
+    const float denom_val = (chan == 0) ? mel_low : center_mel_freqs[chan - 1];
+
+    int j;
+    for (j = 0; j < num_frequencies; ++j, ++frequency) {
+      const float weight =
+          (center_mel_freqs[chan] - FreqToMel(frequency * hz_per_sbin)) /
+          (center_mel_freqs[chan] - denom_val);
+
+      // Make the float into an integer for the weights (and unweights).
+      const int weight_index = weight_start + frequency_offset + j;
+      QuantizeFilterbankWeights(weight, state->weights + weight_index,
+                                state->unweights + weight_index);
+    }
+    if (frequency > state->end_index) {
+      state->end_index = frequency;
+    }
+  }
+
+  if (state->end_index >= spectrum_size) {
+    error_reporter->Report("Filterbank end_index is above spectrum size.");
+    return 0;
+  }
+  return 1;
+}

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/filterbank_util.h

@@ -0,0 +1,42 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_FILTERBANK_UTIL_H_
+#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_FILTERBANK_UTIL_H_
+
+#include "tensorflow/lite/c/c_api_internal.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/filterbank.h"
+#include "tensorflow/lite/experimental/micro/micro_error_reporter.h"
+
+struct FilterbankConfig {
+  // number of frequency channel buckets for filterbank
+  int num_channels;
+  // maximum frequency to include
+  float upper_band_limit;
+  // minimum frequency to include
+  float lower_band_limit;
+  // unused
+  int output_scale_shift;
+};
+
+// Fills the frontendConfig with "sane" defaults.
+void FilterbankFillConfigWithDefaults(struct FilterbankConfig* config);
+
+// Allocates any buffers.
+int FilterbankPopulateState(tflite::ErrorReporter* error_reporter,
+                            const struct FilterbankConfig* config,
+                            struct FilterbankState* state, int sample_rate,
+                            int spectrum_size);
+
+#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_FILTERBANK_UTIL_H_

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/frontend.cc

@@ -0,0 +1,70 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/frontend.h"
+
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/bits.h"
+
+struct FrontendOutput FrontendProcessSamples(struct FrontendState* state,
+                                             const int16_t* samples,
+                                             size_t num_samples,
+                                             size_t* num_samples_read) {
+  struct FrontendOutput output;
+  output.values = nullptr;
+  output.size = 0;
+
+  // Try to apply the window - if it fails, return and wait for more data.
+  if (!WindowProcessSamples(&state->window, samples, num_samples,
+                            num_samples_read)) {
+    return output;
+  }
+
+  // Apply the FFT to the window's output (and scale it so that the fixed point
+  // FFT can have as much resolution as possible).
+  int input_shift =
+      15 - MostSignificantBit32(state->window.max_abs_output_value);
+  FftCompute(&state->fft, state->window.output, input_shift);
+
+  // We can re-ruse the fft's output buffer to hold the energy.
+  int32_t* energy = reinterpret_cast<int32_t*>(state->fft.output);
+  FilterbankConvertFftComplexToEnergy(&state->filterbank, state->fft.output,
+                                      energy);
+  FilterbankAccumulateChannels(&state->filterbank, energy);
+  uint32_t* scaled_filterbank = FilterbankSqrt(&state->filterbank, input_shift);
+
+  // Apply noise reduction.
+  NoiseReductionApply(&state->noise_reduction, scaled_filterbank);
+
+  if (state->pcan_gain_control.enable_pcan) {
+    PcanGainControlApply(&state->pcan_gain_control, scaled_filterbank);
+  }
+
+  // Apply the log and scale.
+  int correction_bits =
+      MostSignificantBit32(state->fft.fft_size) - 1 - (kFilterbankBits / 2);
+  uint16_t* logged_filterbank =
+      LogScaleApply(&state->log_scale, scaled_filterbank,
+                    state->filterbank.num_channels, correction_bits);
+
+  output.size = state->filterbank.num_channels;
+  output.values = logged_filterbank;
+  return output;
+}
+
+void FrontendReset(struct FrontendState* state) {
+  WindowReset(&state->window);
+  FftReset(&state->fft);
+  FilterbankReset(&state->filterbank);
+  NoiseReductionReset(&state->noise_reduction);
+}

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/frontend.h

@@ -0,0 +1,56 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_FRONTEND_H_
+#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_FRONTEND_H_
+
+#include <stdint.h>
+#include <stdlib.h>
+
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/fft.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/filterbank.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/log_scale.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/noise_reduction.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/pcan_gain_control.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/window.h"
+
+struct FrontendState {
+  struct WindowState window;
+  struct FftState fft;
+  struct FilterbankState filterbank;
+  struct NoiseReductionState noise_reduction;
+  struct PcanGainControlState pcan_gain_control;
+  struct LogScaleState log_scale;
+};
+
+struct FrontendOutput {
+  const uint16_t* values;
+  size_t size;
+};
+
+// Main entry point to processing frontend samples. Updates num_samples_read to
+// contain the number of samples that have been consumed from the input array.
+// Returns a struct containing the generated output. If not enough samples were
+// added to generate a feature vector, the returned size will be 0 and the
+// values pointer will be NULL. Note that the output pointer will be invalidated
+// as soon as FrontendProcessSamples is called again, so copy the contents
+// elsewhere if you need to use them later.
+struct FrontendOutput FrontendProcessSamples(struct FrontendState* state,
+                                             const int16_t* samples,
+                                             size_t num_samples,
+                                             size_t* num_samples_read);
+
+void FrontendReset(struct FrontendState* state);
+
+#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_FRONTEND_H_

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/frontend_test.cc

@@ -0,0 +1,134 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/frontend.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/frontend_util.h"
+
+#include "tensorflow/lite/experimental/micro/testing/micro_test.h"
+
+namespace {
+
+const int kSampleRate = 1000;
+const int kWindowSamples = 25;
+const int kStepSamples = 10;
+const int16_t kFakeAudioData[] = {
+    0, 32767, 0, -32768, 0, 32767, 0, -32768, 0, 32767, 0, -32768,
+    0, 32767, 0, -32768, 0, 32767, 0, -32768, 0, 32767, 0, -32768,
+    0, 32767, 0, -32768, 0, 32767, 0, -32768, 0, 32767, 0, -32768};
+
+// Test end-to-end frontend behaviors.
+class FrontendTestConfig {
+ public:
+  FrontendTestConfig() {
+    config_.window.size_ms = 25;
+    config_.window.step_size_ms = 10;
+    config_.noise_reduction.smoothing_bits = 10;
+    config_.filterbank.num_channels = 2;
+    config_.filterbank.lower_band_limit = 8.0;
+    config_.filterbank.upper_band_limit = 450.0;
+    config_.noise_reduction.smoothing_bits = 10;
+    config_.noise_reduction.even_smoothing = 0.025;
+    config_.noise_reduction.odd_smoothing = 0.06;
+    config_.noise_reduction.min_signal_remaining = 0.05;
+    config_.pcan_gain_control.enable_pcan = true;
+    config_.pcan_gain_control.strength = 0.95;
+    config_.pcan_gain_control.offset = 80.0;
+    config_.pcan_gain_control.gain_bits = 21;
+    config_.log_scale.enable_log = true;
+    config_.log_scale.scale_shift = 6;
+  }
+
+  struct FrontendConfig config_;
+};
+
+}  // namespace
+
+TF_LITE_MICRO_TESTS_BEGIN
+
+TF_LITE_MICRO_TEST(FrontendTest_CheckOutputValues) {
+  tflite::MicroErrorReporter micro_error_reporter;
+  tflite::ErrorReporter* error_reporter = &micro_error_reporter;
+
+  FrontendTestConfig config;
+  struct FrontendState state;
+  TF_LITE_MICRO_EXPECT(FrontendPopulateState(error_reporter, &config.config_,
+                                             &state, kSampleRate));
+  size_t num_samples_read;
+
+  struct FrontendOutput output = FrontendProcessSamples(
+      &state, kFakeAudioData,
+      sizeof(kFakeAudioData) / sizeof(kFakeAudioData[0]), &num_samples_read);
+
+  const uint16_t expected[] = {479, 425};
+  TF_LITE_MICRO_EXPECT_EQ(output.size, sizeof(expected) / sizeof(expected[0]));
+  int i;
+  for (i = 0; i < output.size; ++i) {
+    TF_LITE_MICRO_EXPECT_EQ(output.values[i], expected[i]);
+  }
+}
+
+TF_LITE_MICRO_TEST(FrontendTest_CheckConsecutiveWindow) {
+  tflite::MicroErrorReporter micro_error_reporter;
+  tflite::ErrorReporter* error_reporter = &micro_error_reporter;
+
+  FrontendTestConfig config;
+  struct FrontendState state;
+  TF_LITE_MICRO_EXPECT(FrontendPopulateState(error_reporter, &config.config_,
+                                             &state, kSampleRate));
+  size_t num_samples_read;
+
+  FrontendProcessSamples(&state, kFakeAudioData,
+                         sizeof(kFakeAudioData) / sizeof(kFakeAudioData[0]),
+                         &num_samples_read);
+  struct FrontendOutput output = FrontendProcessSamples(
+      &state, kFakeAudioData + kWindowSamples,
+      sizeof(kFakeAudioData) / sizeof(kFakeAudioData[0]) - kWindowSamples,
+      &num_samples_read);
+
+  const int16_t expected[] = {436, 378};
+  TF_LITE_MICRO_EXPECT_EQ(output.size, sizeof(expected) / sizeof(expected[0]));
+  int i;
+  for (i = 0; i < output.size; ++i) {
+    TF_LITE_MICRO_EXPECT_EQ(output.values[i], expected[i]);
+  }
+}
+
+TF_LITE_MICRO_TEST(FrontendTest_CheckNotEnoughSamples) {
+  tflite::MicroErrorReporter micro_error_reporter;
+  tflite::ErrorReporter* error_reporter = &micro_error_reporter;
+
+  FrontendTestConfig config;
+  struct FrontendState state;
+  TF_LITE_MICRO_EXPECT(FrontendPopulateState(error_reporter, &config.config_,
+                                             &state, kSampleRate));
+  size_t num_samples_read;
+
+  FrontendProcessSamples(&state, kFakeAudioData,
+                         sizeof(kFakeAudioData) / sizeof(kFakeAudioData[0]),
+                         &num_samples_read);
+  FrontendProcessSamples(
+      &state, kFakeAudioData + kWindowSamples,
+      sizeof(kFakeAudioData) / sizeof(kFakeAudioData[0]) - kWindowSamples,
+      &num_samples_read);
+  struct FrontendOutput output = FrontendProcessSamples(
+      &state, kFakeAudioData + kWindowSamples + kStepSamples,
+      sizeof(kFakeAudioData) / sizeof(kFakeAudioData[0]) - kWindowSamples -
+          kStepSamples,
+      &num_samples_read);
+
+  TF_LITE_MICRO_EXPECT_EQ(output.size, 0);
+  TF_LITE_MICRO_EXPECT_EQ(output.values, nullptr);
+}
+
+TF_LITE_MICRO_TESTS_END

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/frontend_util.cc

@@ -0,0 +1,80 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/frontend_util.h"
+
+#include <string.h>
+
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/bits.h"
+
+void FrontendFillConfigWithDefaults(struct FrontendConfig* config) {
+  WindowFillConfigWithDefaults(&config->window);
+  FilterbankFillConfigWithDefaults(&config->filterbank);
+  NoiseReductionFillConfigWithDefaults(&config->noise_reduction);
+  PcanGainControlFillConfigWithDefaults(&config->pcan_gain_control);
+  LogScaleFillConfigWithDefaults(&config->log_scale);
+}
+
+int FrontendPopulateState(tflite::ErrorReporter* error_reporter,
+                          const struct FrontendConfig* config,
+                          struct FrontendState* state, int sample_rate) {
+  memset(state, 0, sizeof(*state));
+
+  if (!WindowPopulateState(error_reporter, &config->window, &state->window,
+                           sample_rate)) {
+    error_reporter->Report("Failed to populate window state");
+    return 0;
+  }
+
+  if (!FftPopulateState(error_reporter, &state->fft, state->window.size)) {
+    error_reporter->Report("Failed to populate fft state");
+    return 0;
+  }
+  FftInit(&state->fft);
+
+  if (!FilterbankPopulateState(error_reporter, &config->filterbank,
+                               &state->filterbank, sample_rate,
+                               state->fft.fft_size / 2 + 1)) {
+    error_reporter->Report("Failed to populate filterbank state");
+    return 0;
+  }
+
+  if (!NoiseReductionPopulateState(error_reporter, &config->noise_reduction,
+                                   &state->noise_reduction,
+                                   state->filterbank.num_channels)) {
+    error_reporter->Report("Failed to populate noise reduction state");
+    return 0;
+  }
+
+  int input_correction_bits =
+      MostSignificantBit32(state->fft.fft_size) - 1 - (kFilterbankBits / 2);
+  if (!PcanGainControlPopulateState(
+          error_reporter, &config->pcan_gain_control, &state->pcan_gain_control,
+          state->noise_reduction.estimate, state->filterbank.num_channels,
+          state->noise_reduction.smoothing_bits, input_correction_bits)) {
+    error_reporter->Report("Failed to populate pcan gain control state");
+    return 0;
+  }
+
+  if (!LogScalePopulateState(error_reporter, &config->log_scale,
+                             &state->log_scale)) {
+    error_reporter->Report("Failed to populate log scale state");
+    return 0;
+  }
+
+  FrontendReset(state);
+
+  // All good, return a true value.
+  return 1;
+}

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/frontend_util.h

@@ -0,0 +1,44 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_FRONTEND_UTIL_H_
+#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_FRONTEND_UTIL_H_
+
+#include "tensorflow/lite/c/c_api_internal.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/fft_util.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/filterbank_util.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/frontend.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/log_scale_util.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/noise_reduction_util.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/pcan_gain_control_util.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/window_util.h"
+#include "tensorflow/lite/experimental/micro/micro_error_reporter.h"
+
+struct FrontendConfig {
+  struct WindowConfig window;
+  struct FilterbankConfig filterbank;
+  struct NoiseReductionConfig noise_reduction;
+  struct PcanGainControlConfig pcan_gain_control;
+  struct LogScaleConfig log_scale;
+};
+
+// Fills the frontendConfig with "sane" defaults.
+void FrontendFillConfigWithDefaults(struct FrontendConfig* config);
+
+// Prepares any buffers.
+int FrontendPopulateState(tflite::ErrorReporter* error_reporter,
+                          const struct FrontendConfig* config,
+                          struct FrontendState* state, int sample_rate);
+
+#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_FRONTEND_UTIL_H_

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/log_lut.cc

@@ -0,0 +1,30 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/log_lut.h"
+const uint16_t kLogLut[]
+#ifndef _MSC_VER
+    __attribute__((aligned(4)))
+#endif  // _MSV_VER
+    = {0,    224,  442,  654,  861,  1063, 1259, 1450, 1636, 1817, 1992, 2163,
+       2329, 2490, 2646, 2797, 2944, 3087, 3224, 3358, 3487, 3611, 3732, 3848,
+       3960, 4068, 4172, 4272, 4368, 4460, 4549, 4633, 4714, 4791, 4864, 4934,
+       5001, 5063, 5123, 5178, 5231, 5280, 5326, 5368, 5408, 5444, 5477, 5507,
+       5533, 5557, 5578, 5595, 5610, 5622, 5631, 5637, 5640, 5641, 5638, 5633,
+       5626, 5615, 5602, 5586, 5568, 5547, 5524, 5498, 5470, 5439, 5406, 5370,
+       5332, 5291, 5249, 5203, 5156, 5106, 5054, 5000, 4944, 4885, 4825, 4762,
+       4697, 4630, 4561, 4490, 4416, 4341, 4264, 4184, 4103, 4020, 3935, 3848,
+       3759, 3668, 3575, 3481, 3384, 3286, 3186, 3084, 2981, 2875, 2768, 2659,
+       2549, 2437, 2323, 2207, 2090, 1971, 1851, 1729, 1605, 1480, 1353, 1224,
+       1094, 963,  830,  695,  559,  421,  282,  142,  0,    0};

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/log_lut.h

@@ -0,0 +1,32 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_LOG_LUT_H_
+#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_LOG_LUT_H_
+
+#include <stdint.h>
+
+// Number of segments in the log lookup table. The table will be kLogSegments+1
+// in length (with some padding).
+#define kLogSegments 128
+#define kLogSegmentsLog2 7
+
+// Scale used by lookup table.
+#define kLogScale 65536
+#define kLogScaleLog2 16
+#define kLogCoeff 45426
+
+extern const uint16_t kLogLut[];
+
+#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_LOG_LUT_H_

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/log_scale.cc

@@ -0,0 +1,84 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/log_scale.h"
+
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/bits.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/log_lut.h"
+
+#define kuint16max 0x0000FFFF
+
+// The following functions implement integer logarithms of various sizes. The
+// approximation is calculated according to method described in
+//       www.inti.gob.ar/electronicaeinformatica/instrumentacion/utic/
+//       publicaciones/SPL2007/Log10-spl07.pdf
+// It first calculates log2 of the input and then converts it to natural
+// logarithm.
+
+static uint32_t Log2FractionPart(const uint32_t x, const uint32_t log2x) {
+  // Part 1
+  int32_t frac = x - (1LL << log2x);
+  if (log2x < kLogScaleLog2) {
+    frac <<= kLogScaleLog2 - log2x;
+  } else {
+    frac >>= log2x - kLogScaleLog2;
+  }
+  // Part 2
+  const uint32_t base_seg = frac >> (kLogScaleLog2 - kLogSegmentsLog2);
+  const uint32_t seg_unit =
+      ((static_cast<uint32_t>(1)) << kLogScaleLog2) >> kLogSegmentsLog2;
+
+  const int32_t c0 = kLogLut[base_seg];
+  const int32_t c1 = kLogLut[base_seg + 1];
+  const int32_t seg_base = seg_unit * base_seg;
+  const int32_t rel_pos = ((c1 - c0) * (frac - seg_base)) >> kLogScaleLog2;
+  return frac + c0 + rel_pos;
+}
+
+static uint32_t Log(const uint32_t x, const uint32_t scale_shift) {
+  const uint32_t integer = MostSignificantBit32(x) - 1;
+  const uint32_t fraction = Log2FractionPart(x, integer);
+  const uint32_t log2 = (integer << kLogScaleLog2) + fraction;
+  const uint32_t round = kLogScale / 2;
+  const uint32_t loge =
+      ((static_cast<uint64_t>(kLogCoeff)) * log2 + round) >> kLogScaleLog2;
+  // Finally scale to our output scale
+  const uint32_t loge_scaled = ((loge << scale_shift) + round) >> kLogScaleLog2;
+  return loge_scaled;
+}
+
+uint16_t* LogScaleApply(struct LogScaleState* state, uint32_t* signal,
+                        int signal_size, int correction_bits) {
+  const int scale_shift = state->scale_shift;
+  uint16_t* output = reinterpret_cast<uint16_t*>(signal);
+  uint16_t* ret = output;
+  int i;
+  for (i = 0; i < signal_size; ++i) {
+    uint32_t value = *signal++;
+    if (state->enable_log) {
+      if (correction_bits < 0) {
+        value >>= -correction_bits;
+      } else {
+        value <<= correction_bits;
+      }
+      if (value > 1) {
+        value = Log(value, scale_shift);
+      } else {
+        value = 0;
+      }
+    }
+    *output++ = (value < kuint16max) ? value : kuint16max;
+  }
+  return ret;
+}

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/log_scale.h

@@ -0,0 +1,31 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_LOG_SCALE_H_
+#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_LOG_SCALE_H_
+
+#include <stdint.h>
+#include <stdlib.h>
+
+struct LogScaleState {
+  int enable_log;
+  int scale_shift;
+};
+
+// Applies a fixed point logarithm to the signal and converts it to 16 bit. Note
+// that the signal array will be modified.
+uint16_t* LogScaleApply(struct LogScaleState* state, uint32_t* signal,
+                        int signal_size, int correction_bits);
+
+#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_LOG_SCALE_H_

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/log_scale_test.cc

@@ -0,0 +1,63 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/log_scale.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/log_scale_util.h"
+
+#include "tensorflow/lite/experimental/micro/testing/micro_test.h"
+
+namespace {
+
+const int kScaleShift = 6;
+const int kCorrectionBits = -1;
+
+}  // namespace
+
+TF_LITE_MICRO_TESTS_BEGIN
+
+TF_LITE_MICRO_TEST(LogScaleTest_CheckOutputValues) {
+  struct LogScaleState state;
+  state.enable_log = true;
+  state.scale_shift = kScaleShift;
+
+  uint32_t fake_signal[] = {3578, 1533};
+  uint16_t* output = LogScaleApply(&state, fake_signal,
+                                   sizeof(fake_signal) / sizeof(fake_signal[0]),
+                                   kCorrectionBits);
+
+  const uint16_t expected[] = {479, 425};
+  int i;
+  for (i = 0; i < sizeof(expected) / sizeof(expected[0]); ++i) {
+    TF_LITE_MICRO_EXPECT_EQ(output[i], expected[i]);
+  }
+}
+
+TF_LITE_MICRO_TEST(LogScaleTest_CheckOutputValuesNoLog) {
+  struct LogScaleState state;
+  state.enable_log = false;
+  state.scale_shift = kScaleShift;
+
+  uint32_t fake_signal[] = {85964, 45998};
+  uint16_t* output = LogScaleApply(&state, fake_signal,
+                                   sizeof(fake_signal) / sizeof(fake_signal[0]),
+                                   kCorrectionBits);
+
+  const uint16_t expected[] = {65535, 45998};
+  int i;
+  for (i = 0; i < sizeof(expected) / sizeof(expected[0]); ++i) {
+    TF_LITE_MICRO_EXPECT_EQ(output[i], expected[i]);
+  }
+}
+
+TF_LITE_MICRO_TESTS_END

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/log_scale_util.cc

@@ -0,0 +1,28 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/log_scale_util.h"
+
+void LogScaleFillConfigWithDefaults(struct LogScaleConfig* config) {
+  config->enable_log = 1;
+  config->scale_shift = 6;
+}
+
+int LogScalePopulateState(tflite::ErrorReporter* error_reporter,
+                          const struct LogScaleConfig* config,
+                          struct LogScaleState* state) {
+  state->enable_log = config->enable_log;
+  state->scale_shift = config->scale_shift;
+  return 1;
+}

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/log_scale_util.h

@@ -0,0 +1,40 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_LOG_SCALE_UTIL_H_
+#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_LOG_SCALE_UTIL_H_
+
+#include <stdint.h>
+#include <stdlib.h>
+
+#include "tensorflow/lite/c/c_api_internal.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/log_scale.h"
+#include "tensorflow/lite/experimental/micro/micro_error_reporter.h"
+
+struct LogScaleConfig {
+  // set to false (0) to disable this module
+  int enable_log;
+  // scale results by 2^(scale_shift)
+  int scale_shift;
+};
+
+// Populates the LogScaleConfig with "sane" default values.
+void LogScaleFillConfigWithDefaults(struct LogScaleConfig* config);
+
+// Allocates any buffers.
+int LogScalePopulateState(tflite::ErrorReporter* error_reporter,
+                          const struct LogScaleConfig* config,
+                          struct LogScaleState* state);
+
+#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_LOG_SCALE_UTIL_H_

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/micro_features_generator.cc

@@ -0,0 +1,99 @@
+/* Copyright 2019 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/micro_features_generator.h"
+
+#include <cmath>
+#include <cstring>
+
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/frontend.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/frontend_util.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/micro_model_settings.h"
+
+namespace {
+
+FrontendState g_micro_features_state;
+bool g_is_first_time = true;
+
+}  // namespace
+
+TfLiteStatus InitializeMicroFeatures(tflite::ErrorReporter* error_reporter) {
+  FrontendConfig config;
+  config.window.size_ms = kFeatureSliceDurationMs;
+  config.window.step_size_ms = kFeatureSliceStrideMs;
+  config.noise_reduction.smoothing_bits = 10;
+  config.filterbank.num_channels = kFeatureSliceSize;
+  config.filterbank.lower_band_limit = 125.0;
+  config.filterbank.upper_band_limit = 7500.0;
+  config.noise_reduction.smoothing_bits = 10;
+  config.noise_reduction.even_smoothing = 0.025;
+  config.noise_reduction.odd_smoothing = 0.06;
+  config.noise_reduction.min_signal_remaining = 0.05;
+  config.pcan_gain_control.enable_pcan = 1;
+  config.pcan_gain_control.strength = 0.95;
+  config.pcan_gain_control.offset = 80.0;
+  config.pcan_gain_control.gain_bits = 21;
+  config.log_scale.enable_log = 1;
+  config.log_scale.scale_shift = 6;
+  if (!FrontendPopulateState(error_reporter, &config, &g_micro_features_state,
+                             kAudioSampleFrequency)) {
+    error_reporter->Report("FrontendPopulateState() failed");
+    return kTfLiteError;
+  }
+  g_is_first_time = true;
+  return kTfLiteOk;
+}
+
+// This is not exposed in any header, and is only used for testing, to ensure
+// that the state is correctly set up before generating results.
+void SetMicroFeaturesNoiseEstimates(const uint32_t* estimate_presets) {
+  for (int i = 0; i < g_micro_features_state.filterbank.num_channels; ++i) {
+    g_micro_features_state.noise_reduction.estimate[i] = estimate_presets[i];
+  }
+}
+
+TfLiteStatus GenerateMicroFeatures(tflite::ErrorReporter* error_reporter,
+                                   const int16_t* input, int input_size,
+                                   int output_size, uint8_t* output,
+                                   size_t* num_samples_read) {
+  const int16_t* frontend_input;
+  if (g_is_first_time) {
+    frontend_input = input;
+    g_is_first_time = false;
+  } else {
+    frontend_input = input + 160;
+  }
+  FrontendOutput frontend_output = FrontendProcessSamples(
+      &g_micro_features_state, frontend_input, input_size, num_samples_read);
+
+  for (int i = 0; i < frontend_output.size; ++i) {
+    // These scaling values are derived from those used in input_data.py in the
+    // training pipeline.
+    constexpr int32_t value_scale = (10 * 255);
+    constexpr int32_t value_div = (256 * 26);
+    int32_t value =
+        ((frontend_output.values[i] * value_scale) + (value_div / 2)) /
+        value_div;
+    if (value < 0) {
+      value = 0;
+    }
+    if (value > 255) {
+      value = 255;
+    }
+    output[i] = value;
+  }
+
+  return kTfLiteOk;
+}

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/micro_features_generator.h

@@ -0,0 +1,32 @@
+/* Copyright 2019 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+
+#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_MICRO_FEATURES_GENERATOR_H_
+#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_MICRO_FEATURES_GENERATOR_H_
+
+#include "tensorflow/lite/c/c_api_internal.h"
+#include "tensorflow/lite/experimental/micro/micro_error_reporter.h"
+
+// Sets up any resources needed for the feature generation pipeline.
+TfLiteStatus InitializeMicroFeatures(tflite::ErrorReporter* error_reporter);
+
+// Converts audio sample data into a more compact form that's appropriate for
+// feeding into a neural network.
+TfLiteStatus GenerateMicroFeatures(tflite::ErrorReporter* error_reporter,
+                                   const int16_t* input, int input_size,
+                                   int output_size, uint8_t* output,
+                                   size_t* num_samples_read);
+
+#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_MICRO_FEATURES_GENERATOR_H_

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/micro_features_generator_test.cc

@@ -0,0 +1,100 @@
+/* Copyright 2019 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/micro_features_generator.h"
+#include "tensorflow/lite/c/c_api_internal.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/no_feature_data_slice.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/yes_feature_data_slice.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/no_30ms_sample_data.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/yes_30ms_sample_data.h"
+#include "tensorflow/lite/experimental/micro/micro_error_reporter.h"
+#include "tensorflow/lite/experimental/micro/testing/micro_test.h"
+
+// This is a test-only API, not exposed in any public headers, so declare it.
+void SetMicroFeaturesNoiseEstimates(const uint32_t* estimate_presets);
+
+TF_LITE_MICRO_TESTS_BEGIN
+
+TF_LITE_MICRO_TEST(TestMicroFeaturesGeneratorYes) {
+  tflite::MicroErrorReporter micro_error_reporter;
+  tflite::ErrorReporter* error_reporter = &micro_error_reporter;
+
+  TF_LITE_MICRO_EXPECT_EQ(kTfLiteOk, InitializeMicroFeatures(error_reporter));
+
+  // The micro features pipeline retains state from previous calls to help
+  // estimate the background noise. Unfortunately this makes it harder to
+  // exactly reproduce results in a test environment, so use a known snapshot
+  // of the parameters at the point that the golden feature values were
+  // created.
+  const uint32_t yes_estimate_presets[] = {
+      1062898, 2644477, 1257642, 1864718, 412722, 725703, 395721, 474082,
+      173046,  255856,  158966,  153736,  69181,  199100, 144493, 227740,
+      110573,  164330,  79666,   144650,  122947, 476799, 398553, 497493,
+      322152,  1140005, 566716,  690605,  308902, 347481, 109891, 170457,
+      73901,   100975,  42963,   72325,   34183,  20207,  6640,   9468,
+  };
+  SetMicroFeaturesNoiseEstimates(yes_estimate_presets);
+
+  uint8_t yes_calculated_data[g_yes_feature_data_slice_size];
+  size_t num_samples_read;
+  TfLiteStatus yes_status = GenerateMicroFeatures(
+      error_reporter, g_yes_30ms_sample_data, g_yes_30ms_sample_data_size,
+      g_yes_feature_data_slice_size, yes_calculated_data, &num_samples_read);
+  TF_LITE_MICRO_EXPECT_EQ(kTfLiteOk, yes_status);
+
+  for (int i = 0; i < g_yes_feature_data_slice_size; ++i) {
+    TF_LITE_MICRO_EXPECT_EQ(g_yes_feature_data_slice[i],
+                            yes_calculated_data[i]);
+    if (g_yes_feature_data_slice[i] != yes_calculated_data[i]) {
+      error_reporter->Report("Expected value %d but found %d",
+                             g_yes_feature_data_slice[i],
+                             yes_calculated_data[i]);
+    }
+  }
+}
+
+TF_LITE_MICRO_TEST(TestMicroFeaturesGeneratorNo) {
+  tflite::MicroErrorReporter micro_error_reporter;
+  tflite::ErrorReporter* error_reporter = &micro_error_reporter;
+
+  TF_LITE_MICRO_EXPECT_EQ(kTfLiteOk, InitializeMicroFeatures(error_reporter));
+  // As we did for the previous features, set known good noise state
+  // parameters.
+  const uint32_t no_estimate_presets[] = {
+      2563964, 1909393, 559801, 538670, 203643, 175959, 75088, 139491,
+      59691,   95307,   43865,  129263, 52517,  80058,  51330, 100731,
+      76674,   76262,   15497,  22598,  13778,  21460,  8946,  17806,
+      10023,   18810,   8002,   10842,  7578,   9983,   6267,  10759,
+      8946,    18488,   9691,   39785,  9939,   17835,  9671,  18512,
+  };
+  SetMicroFeaturesNoiseEstimates(no_estimate_presets);
+
+  uint8_t no_calculated_data[g_no_feature_data_slice_size];
+  size_t num_samples_read;
+  TfLiteStatus no_status = GenerateMicroFeatures(
+      error_reporter, g_no_30ms_sample_data, g_no_30ms_sample_data_size,
+      g_no_feature_data_slice_size, no_calculated_data, &num_samples_read);
+  TF_LITE_MICRO_EXPECT_EQ(kTfLiteOk, no_status);
+
+  for (int i = 0; i < g_no_feature_data_slice_size; ++i) {
+    TF_LITE_MICRO_EXPECT_EQ(g_no_feature_data_slice[i], no_calculated_data[i]);
+    if (g_no_feature_data_slice[i] != no_calculated_data[i]) {
+      error_reporter->Report("Expected value %d but found %d",
+                             g_no_feature_data_slice[i], no_calculated_data[i]);
+    }
+  }
+}
+
+TF_LITE_MICRO_TESTS_END

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/micro_model_settings.cc

@@ -13,7 +13,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 ==============================================================================*/
 
-#include "tensorflow/lite/experimental/micro/examples/micro_speech/model_settings.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/micro_model_settings.h"
 
 const char* kCategoryLabels[kCategoryCount] = {
     "silence",

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/micro_model_settings.h

@@ -0,0 +1,41 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+
+#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_MICRO_MODEL_SETTINGS_H_
+#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_MICRO_MODEL_SETTINGS_H_
+
+// Keeping these as constant expressions allow us to allocate fixed-sized arrays
+// on the stack for our working memory.
+
+// The size of the input time series data we pass to the FFT to produce the
+// frequency information. This has to be a power of two, and since we're dealing
+// with 30ms of 16KHz inputs, which means 480 samples, this is the next value.
+constexpr int kMaxAudioSampleSize = 512;
+constexpr int kAudioSampleFrequency = 16000;
+
+// All of these values are derived from the values used during model training,
+// if you change your model you'll need to update these constants.
+constexpr int kFeatureSliceSize = 40;
+constexpr int kFeatureSliceCount = 49;
+constexpr int kFeatureElementCount = (kFeatureSliceSize * kFeatureSliceCount);
+constexpr int kFeatureSliceStrideMs = 20;
+constexpr int kFeatureSliceDurationMs = 30;
+
+constexpr int kCategoryCount = 4;
+constexpr int kSilenceIndex = 0;
+constexpr int kUnknownIndex = 1;
+extern const char* kCategoryLabels[kCategoryCount];
+
+#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_MICRO_MODEL_SETTINGS_H_

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/no_feature_data_slice.cc

@@ -0,0 +1,24 @@
+/* Copyright 2019 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+
+// See the header for documentation on the meaning of this data.
+
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/no_feature_data_slice.h"
+
+const uint8_t g_no_feature_data_slice[g_no_feature_data_slice_size] = {
+    216, 195, 223, 211, 238, 223, 243, 215, 226, 204, 232, 211, 232, 213,
+    240, 218, 235, 214, 238, 205, 207, 173, 149, 201, 215, 200, 230, 213,
+    208, 195, 175, 151, 195, 175, 182, 163, 235, 217, 218, 190,
+};

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/no_feature_data_slice.h

@@ -0,0 +1,29 @@
+/* Copyright 2019 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+
+// This data was extracted from the larger feature data held in
+// no_features_data.cc and consists of the 29th spectrogram slice of 43 values.
+// This is the expected result of running the sample data in
+// no_30ms_sample_data.cc through through the preprocessing pipeline.
+
+#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_NO_FEATURE_DATA_SLICE_H_
+#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_NO_FEATURE_DATA_SLICE_H_
+
+#include <cstdint>
+
+constexpr int g_no_feature_data_slice_size = 40;
+extern const uint8_t g_no_feature_data_slice[];
+
+#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_NO_FEATURE_DATA_SLICE_H_

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/no_micro_features_data.cc

@@ -0,0 +1,165 @@
+/* Copyright 2019 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/no_micro_features_data.h"
+
+/* File automatically created by
+ * tensorflow/examples/speech_commands/wav_to_features.py \
+ * --sample_rate=16000 \
+ * --clip_duration_ms=1000 \
+ * --window_size_ms=30 \
+ * --window_stride_ms=20 \
+ * --feature_bin_count=40 \
+ * --quantize=1 \
+ * --preprocess="micro" \
+ * --input_wav="speech_commands_test_set_v0.02/no/f9643d42_nohash_4.wav" \
+ * --output_c_file="/tmp/no_micro_features_data.cc" \
+ */
+
+const int g_no_micro_f9643d42_nohash_4_width = 40;
+const int g_no_micro_f9643d42_nohash_4_height = 49;
+const unsigned char g_no_micro_f9643d42_nohash_4_data[] = {
+    230, 205, 191, 203, 202, 181, 180, 194, 205, 187, 183, 197, 203, 198, 196,
+    186, 202, 159, 151, 126, 110, 138, 141, 142, 137, 148, 133, 120, 110, 126,
+    117, 110, 117, 116, 137, 134, 95,  116, 123, 110, 184, 144, 183, 189, 197,
+    172, 188, 164, 194, 179, 175, 174, 182, 173, 184, 174, 200, 145, 154, 148,
+    147, 135, 143, 122, 127, 138, 116, 99,  122, 105, 110, 125, 127, 133, 131,
+    123, 116, 119, 127, 114, 193, 176, 185, 170, 175, 146, 166, 167, 185, 185,
+    185, 183, 195, 185, 176, 178, 197, 155, 137, 144, 164, 132, 153, 132, 138,
+    137, 134, 95,  120, 116, 131, 122, 99,  120, 120, 110, 116, 110, 126, 127,
+    128, 159, 187, 119, 178, 187, 197, 167, 199, 184, 180, 165, 194, 176, 144,
+    134, 187, 136, 142, 134, 145, 132, 145, 105, 119, 123, 125, 116, 125, 102,
+    129, 138, 130, 99,  99,  90,  120, 123, 134, 95,  194, 172, 187, 123, 191,
+    179, 195, 182, 201, 137, 167, 142, 185, 161, 187, 146, 167, 152, 154, 107,
+    152, 112, 134, 144, 117, 116, 105, 85,  105, 105, 99,  90,  123, 112, 112,
+    68,  107, 105, 117, 99,  116, 143, 139, 90,  154, 142, 188, 172, 178, 135,
+    175, 149, 177, 110, 173, 160, 169, 162, 173, 119, 132, 110, 85,  85,  117,
+    129, 117, 112, 117, 51,  112, 95,  139, 102, 105, 90,  128, 119, 112, 99,
+    170, 168, 195, 152, 174, 173, 180, 0,   157, 130, 169, 149, 149, 123, 170,
+    130, 170, 133, 159, 102, 134, 90,  85,  105, 126, 119, 130, 90,  78,  68,
+    127, 120, 95,  51,  122, 110, 112, 78,  116, 95,  180, 135, 179, 146, 179,
+    162, 197, 153, 172, 135, 154, 0,   149, 95,  145, 114, 166, 0,   114, 110,
+    145, 107, 114, 90,  136, 68,  95,  95,  95,  85,  116, 99,  116, 0,   95,
+    68,  102, 51,  102, 78,  185, 157, 138, 158, 180, 117, 173, 142, 145, 117,
+    169, 130, 159, 99,  138, 123, 169, 90,  78,  0,   123, 85,  107, 51,  114,
+    102, 95,  0,   116, 85,  119, 95,  95,  68,  85,  51,  116, 68,  102, 78,
+    167, 105, 164, 163, 178, 126, 164, 154, 154, 51,  177, 120, 156, 85,  134,
+    139, 168, 90,  161, 102, 114, 116, 122, 95,  112, 102, 107, 51,  114, 85,
+    119, 78,  114, 90,  102, 51,  102, 51,  114, 99,  177, 68,  152, 102, 184,
+    166, 179, 129, 177, 129, 180, 110, 158, 105, 139, 0,   145, 85,  148, 102,
+    117, 102, 116, 0,   78,  68,  90,  51,  107, 85,  78,  0,   51,  0,   51,
+    0,   95,  51,  107, 68,  180, 117, 90,  0,   138, 0,   187, 146, 119, 140,
+    164, 90,  136, 0,   131, 51,  159, 99,  141, 138, 116, 51,  90,  51,  90,
+    68,  105, 0,   85,  78,  112, 51,  122, 95,  128, 68,  85,  0,   112, 68,
+    147, 126, 178, 146, 171, 130, 190, 147, 188, 123, 170, 78,  132, 0,   130,
+    125, 159, 95,  102, 0,   110, 0,   95,  85,  120, 68,  78,  51,  99,  51,
+    105, 0,   112, 102, 105, 68,  90,  51,  90,  0,   127, 95,  166, 175, 187,
+    133, 135, 0,   171, 139, 132, 128, 140, 51,  126, 107, 161, 0,   95,  51,
+    119, 0,   114, 0,   95,  110, 116, 51,  112, 0,   90,  0,   116, 51,  68,
+    0,   105, 68,  105, 0,   164, 78,  173, 0,   194, 166, 145, 114, 116, 51,
+    107, 122, 151, 0,   156, 102, 148, 51,  122, 95,  129, 0,   85,  0,   127,
+    78,  90,  0,   78,  0,   95,  0,   110, 0,   68,  119, 120, 68,  68,  0,
+    122, 99,  147, 127, 200, 167, 85,  114, 161, 85,  161, 125, 143, 99,  156,
+    85,  147, 68,  99,  0,   107, 102, 132, 51,  112, 68,  95,  78,  99,  0,
+    68,  0,   51,  0,   90,  78,  128, 51,  95,  0,   166, 136, 174, 138, 189,
+    144, 130, 129, 138, 134, 132, 120, 134, 0,   51,  78,  147, 51,  51,  0,
+    51,  0,   78,  0,   68,  68,  95,  78,  90,  0,   0,   0,   68,  0,   90,
+    68,  110, 0,   95,  51,  165, 151, 157, 0,   0,   0,   112, 0,   112, 95,
+    149, 107, 119, 68,  126, 68,  138, 0,   78,  0,   78,  0,   99,  51,  112,
+    0,   102, 0,   78,  51,  85,  0,   0,   0,   78,  0,   95,  0,   95,  78,
+    105, 0,   152, 0,   0,   51,  132, 105, 159, 0,   129, 102, 114, 0,   138,
+    51,  123, 0,   129, 78,  119, 51,  51,  51,  105, 0,   78,  85,  95,  0,
+    85,  0,   0,   0,   85,  0,   78,  0,   0,   0,   172, 142, 141, 0,   137,
+    0,   148, 128, 157, 120, 146, 120, 120, 0,   95,  78,  141, 68,  68,  0,
+    68,  0,   90,  0,   85,  0,   107, 0,   78,  0,   85,  51,  102, 0,   68,
+    78,  68,  0,   51,  0,   125, 0,   141, 51,  102, 138, 175, 51,  120, 51,
+    173, 85,  116, 141, 164, 68,  150, 123, 133, 51,  114, 0,   117, 68,  150,
+    51,  116, 68,  78,  0,   68,  0,   68,  0,   85,  0,   78,  0,   51,  78,
+    155, 90,  161, 0,   132, 99,  123, 78,  107, 0,   134, 90,  95,  0,   78,
+    0,   162, 143, 85,  0,   107, 78,  125, 90,  90,  51,  51,  0,   85,  0,
+    0,   0,   132, 102, 102, 154, 128, 0,   99,  68,  162, 102, 151, 0,   99,
+    51,  147, 141, 156, 0,   112, 120, 158, 127, 145, 139, 187, 171, 135, 138,
+    146, 0,   95,  68,  127, 0,   85,  0,   105, 0,   0,   0,   187, 170, 162,
+    188, 165, 51,  51,  78,  243, 215, 225, 196, 205, 181, 205, 168, 176, 134,
+    157, 110, 126, 114, 133, 139, 193, 163, 159, 116, 160, 126, 122, 127, 171,
+    99,  114, 68,  123, 85,  90,  0,   157, 146, 166, 179, 136, 0,   116, 90,
+    242, 219, 240, 204, 216, 164, 188, 171, 176, 164, 154, 158, 190, 157, 190,
+    141, 182, 177, 169, 128, 172, 145, 105, 129, 157, 90,  78,  51,  119, 68,
+    137, 68,  116, 78,  141, 132, 151, 122, 156, 140, 234, 206, 229, 201, 216,
+    174, 191, 144, 162, 85,  122, 157, 194, 167, 204, 149, 180, 166, 166, 139,
+    122, 133, 156, 126, 145, 85,  128, 0,   99,  51,  145, 0,   126, 51,  166,
+    162, 166, 162, 177, 157, 228, 198, 221, 197, 214, 177, 173, 166, 173, 139,
+    185, 191, 202, 163, 205, 172, 206, 189, 135, 68,  166, 134, 149, 134, 135,
+    90,  127, 107, 175, 90,  136, 117, 135, 140, 172, 167, 166, 149, 177, 152,
+    221, 191, 215, 194, 211, 0,   156, 147, 182, 178, 208, 163, 190, 157, 208,
+    200, 195, 164, 179, 154, 181, 150, 143, 99,  132, 137, 185, 143, 163, 85,
+    51,  107, 132, 134, 164, 127, 167, 159, 175, 141, 216, 195, 223, 211, 238,
+    223, 243, 215, 226, 204, 232, 211, 232, 213, 240, 218, 235, 214, 238, 205,
+    207, 173, 149, 201, 215, 200, 230, 213, 208, 195, 175, 151, 195, 175, 182,
+    163, 235, 217, 218, 190, 211, 191, 215, 191, 217, 220, 241, 215, 229, 206,
+    236, 210, 227, 216, 236, 188, 183, 149, 202, 189, 208, 172, 191, 201, 220,
+    193, 221, 207, 216, 208, 201, 131, 170, 187, 229, 197, 211, 194, 226, 201,
+    205, 184, 206, 177, 221, 210, 226, 184, 204, 197, 218, 198, 212, 209, 213,
+    141, 172, 110, 175, 167, 180, 156, 213, 188, 192, 179, 213, 205, 204, 174,
+    200, 147, 162, 181, 203, 167, 198, 187, 210, 164, 196, 169, 189, 168, 224,
+    198, 213, 204, 198, 195, 230, 211, 221, 197, 208, 0,   0,   0,   85,  90,
+    167, 130, 175, 173, 203, 164, 193, 144, 170, 145, 185, 148, 154, 139, 198,
+    159, 180, 171, 216, 174, 178, 161, 166, 136, 216, 184, 215, 197, 199, 190,
+    228, 195, 208, 51,  117, 0,   0,   0,   0,   0,   140, 51,  135, 154, 188,
+    155, 168, 0,   90,  0,   156, 85,  110, 0,   174, 90,  172, 154, 179, 99,
+    142, 166, 179, 157, 177, 95,  192, 142, 204, 198, 217, 147, 173, 0,   112,
+    0,   0,   0,   0,   0,   0,   0,   110, 0,   107, 0,   160, 0,   148, 95,
+    172, 0,   0,   0,   116, 0,   122, 114, 170, 0,   0,   0,   0,   0,   179,
+    110, 196, 85,  205, 183, 169, 0,   99,  0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   141, 0,   112, 0,   0,   0,   134, 0,   0,   0,   0,
+    0,   0,   0,   139, 0,   0,   0,   0,   112, 186, 78,  163, 0,   169, 128,
+    174, 0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   95,
+    0,   105, 0,   0,   0,   105, 0,   0,   0,   0,   0,   0,   0,   95,  0,
+    0,   0,   0,   0,   0,   0,   119, 0,   164, 78,  0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   90,  0,   0,   68,
+    117, 0,   0,   0,   0,   0,   0,   0,   148, 0,   0,   0,   0,   0,   0,
+    0,   0,   0,   116, 0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   51,
+    0,   0,   0,   99,  0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   99,  0,   0,   0,   0,   0,   0,   0,   0,   0,   78,  0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+};

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/no_micro_features_data.h

@@ -0,0 +1,23 @@
+/* Copyright 2019 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+
+#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_NO_MICRO_FEATURES_DATA_H_
+#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_NO_MICRO_FEATURES_DATA_H_
+
+extern const int g_no_micro_f9643d42_nohash_4_width;
+extern const int g_no_micro_f9643d42_nohash_4_height;
+extern const unsigned char g_no_micro_f9643d42_nohash_4_data[];
+
+#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_NO_MICRO_FEATURES_DATA_H_

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/noise_reduction.cc

@@ -0,0 +1,51 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/noise_reduction.h"
+
+#include <string.h>
+
+void NoiseReductionApply(struct NoiseReductionState* state, uint32_t* signal) {
+  int i;
+  for (i = 0; i < state->num_channels; ++i) {
+    const uint32_t smoothing =
+        ((i & 1) == 0) ? state->even_smoothing : state->odd_smoothing;
+    const uint32_t one_minus_smoothing = (1 << kNoiseReductionBits) - smoothing;
+
+    // Update the estimate of the noise.
+    const uint32_t signal_scaled_up = signal[i] << state->smoothing_bits;
+    uint32_t estimate =
+        ((static_cast<uint64_t>(signal_scaled_up) * smoothing) +
+         (static_cast<uint64_t>(state->estimate[i]) * one_minus_smoothing)) >>
+        kNoiseReductionBits;
+    state->estimate[i] = estimate;
+
+    // Make sure that we can't get a negative value for the signal - estimate.
+    if (estimate > signal_scaled_up) {
+      estimate = signal_scaled_up;
+    }
+
+    const uint32_t floor =
+        (static_cast<uint64_t>(signal[i]) * state->min_signal_remaining) >>
+        kNoiseReductionBits;
+    const uint32_t subtracted =
+        (signal_scaled_up - estimate) >> state->smoothing_bits;
+    const uint32_t output = subtracted > floor ? subtracted : floor;
+    signal[i] = output;
+  }
+}
+
+void NoiseReductionReset(struct NoiseReductionState* state) {
+  memset(state->estimate, 0, sizeof(*state->estimate) * state->num_channels);
+}

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/noise_reduction.h

@@ -0,0 +1,40 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_NOISE_REDUCTION_H_
+#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_NOISE_REDUCTION_H_
+
+#define kNoiseReductionBits 14
+
+#include <stdint.h>
+#include <stdlib.h>
+
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/micro_model_settings.h"
+
+struct NoiseReductionState {
+  int smoothing_bits;
+  uint16_t even_smoothing;
+  uint16_t odd_smoothing;
+  uint16_t min_signal_remaining;
+  int num_channels;
+  uint32_t estimate[kFeatureSliceSize];
+};
+
+// Removes stationary noise from each channel of the signal using a low pass
+// filter.
+void NoiseReductionApply(struct NoiseReductionState* state, uint32_t* signal);
+
+void NoiseReductionReset(struct NoiseReductionState* state);
+
+#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_NOISE_REDUCTION_H_

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/noise_reduction_test.cc

@@ -0,0 +1,83 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/noise_reduction.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/noise_reduction_util.h"
+
+#include "tensorflow/lite/experimental/micro/testing/micro_test.h"
+
+namespace {
+
+const int kNumChannels = 2;
+
+// Test noise reduction using default config values.
+class NoiseReductionTestConfig {
+ public:
+  NoiseReductionTestConfig() {
+    config_.smoothing_bits = 10;
+    config_.even_smoothing = 0.025;
+    config_.odd_smoothing = 0.06;
+    config_.min_signal_remaining = 0.05;
+  }
+
+  struct NoiseReductionConfig config_;
+};
+
+}  // namespace
+
+TF_LITE_MICRO_TESTS_BEGIN
+
+TF_LITE_MICRO_TEST(NoiseReductionTest_TestNoiseReductionEstimate) {
+  tflite::MicroErrorReporter micro_error_reporter;
+  tflite::ErrorReporter* error_reporter = &micro_error_reporter;
+
+  NoiseReductionTestConfig config;
+  struct NoiseReductionState state;
+  TF_LITE_MICRO_EXPECT(NoiseReductionPopulateState(
+      error_reporter, &config.config_, &state, kNumChannels));
+
+  uint32_t signal[] = {247311, 508620};
+  NoiseReductionApply(&state, signal);
+
+  const uint32_t expected[] = {6321887, 31248341};
+  TF_LITE_MICRO_EXPECT_EQ(state.num_channels,
+                          sizeof(expected) / sizeof(expected[0]));
+  int i;
+  for (i = 0; i < state.num_channels; ++i) {
+    TF_LITE_MICRO_EXPECT_EQ(state.estimate[i], expected[i]);
+  }
+}
+
+TF_LITE_MICRO_TEST(NoiseReductionTest_TestNoiseReduction) {
+  tflite::MicroErrorReporter micro_error_reporter;
+  tflite::ErrorReporter* error_reporter = &micro_error_reporter;
+
+  NoiseReductionTestConfig config;
+  struct NoiseReductionState state;
+  TF_LITE_MICRO_EXPECT(NoiseReductionPopulateState(
+      error_reporter, &config.config_, &state, kNumChannels));
+
+  uint32_t signal[] = {247311, 508620};
+  NoiseReductionApply(&state, signal);
+
+  const uint32_t expected[] = {241137, 478104};
+  TF_LITE_MICRO_EXPECT_EQ(state.num_channels,
+                          sizeof(expected) / sizeof(expected[0]));
+  int i;
+  for (i = 0; i < state.num_channels; ++i) {
+    TF_LITE_MICRO_EXPECT_EQ(signal[i], expected[i]);
+  }
+}
+
+TF_LITE_MICRO_TESTS_END

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/noise_reduction_util.cc

@@ -0,0 +1,42 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/noise_reduction_util.h"
+
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/static_alloc.h"
+
+void NoiseReductionFillConfigWithDefaults(struct NoiseReductionConfig* config) {
+  config->smoothing_bits = 10;
+  config->even_smoothing = 0.025;
+  config->odd_smoothing = 0.06;
+  config->min_signal_remaining = 0.05;
+}
+
+int NoiseReductionPopulateState(tflite::ErrorReporter* error_reporter,
+                                const struct NoiseReductionConfig* config,
+                                struct NoiseReductionState* state,
+                                int num_channels) {
+  state->smoothing_bits = config->smoothing_bits;
+  state->odd_smoothing = config->odd_smoothing * (1 << kNoiseReductionBits);
+  state->even_smoothing = config->even_smoothing * (1 << kNoiseReductionBits);
+  state->min_signal_remaining =
+      config->min_signal_remaining * (1 << kNoiseReductionBits);
+  state->num_channels = num_channels;
+  STATIC_ALLOC_ENSURE_ARRAY_SIZE(
+      state->estimate, (state->num_channels * sizeof(*state->estimate)));
+  for (int i = 0; i < state->num_channels; ++i) {
+    state->estimate[i] = 0;
+  }
+  return 1;
+}

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/noise_reduction_util.h

@@ -0,0 +1,42 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_NOISE_REDUCTION_UTIL_H_
+#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_NOISE_REDUCTION_UTIL_H_
+
+#include "tensorflow/lite/c/c_api_internal.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/noise_reduction.h"
+#include "tensorflow/lite/experimental/micro/micro_error_reporter.h"
+
+struct NoiseReductionConfig {
+  // scale the signal up by 2^(smoothing_bits) before reduction
+  int smoothing_bits;
+  // smoothing coefficient for even-numbered channels
+  float even_smoothing;
+  // smoothing coefficient for odd-numbered channels
+  float odd_smoothing;
+  // fraction of signal to preserve (1.0 disables this module)
+  float min_signal_remaining;
+};
+
+// Populates the NoiseReductionConfig with "sane" default values.
+void NoiseReductionFillConfigWithDefaults(struct NoiseReductionConfig* config);
+
+// Prepares any buffers.
+int NoiseReductionPopulateState(tflite::ErrorReporter* error_reporter,
+                                const struct NoiseReductionConfig* config,
+                                struct NoiseReductionState* state,
+                                int num_channels);
+
+#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_NOISE_REDUCTION_UTIL_H_

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/pcan_gain_control.cc

@@ -0,0 +1,57 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/pcan_gain_control.h"
+
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/bits.h"
+
+int16_t WideDynamicFunction(const uint32_t x, const int16_t* lut) {
+  if (x <= 2) {
+    return lut[x];
+  }
+
+  const int16_t interval = MostSignificantBit32(x);
+  lut += 4 * interval - 6;
+
+  const int16_t frac =
+      ((interval < 11) ? (x << (11 - interval)) : (x >> (interval - 11))) &
+      0x3FF;
+
+  int32_t result = (static_cast<int32_t>(lut[2]) * frac) >> 5;
+  result += (static_cast<int32_t>(lut[1])) << 5;
+  result *= frac;
+  result = (result + (1 << 14)) >> 15;
+  result += lut[0];
+  return static_cast<int16_t>(result);
+}
+
+uint32_t PcanShrink(const uint32_t x) {
+  if (x < (2 << kPcanSnrBits)) {
+    return (x * x) >> (2 + 2 * kPcanSnrBits - kPcanOutputBits);
+  } else {
+    return (x >> (kPcanSnrBits - kPcanOutputBits)) - (1 << kPcanOutputBits);
+  }
+}
+
+void PcanGainControlApply(struct PcanGainControlState* state,
+                          uint32_t* signal) {
+  int i;
+  for (i = 0; i < state->num_channels; ++i) {
+    const uint32_t gain =
+        WideDynamicFunction(state->noise_estimate[i], state->gain_lut);
+    const uint32_t snr =
+        (static_cast<uint64_t>(signal[i]) * gain) >> state->snr_shift;
+    signal[i] = PcanShrink(snr);
+  }
+}

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/pcan_gain_control.h

@@ -0,0 +1,41 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_PCAN_GAIN_CONTROL_H_
+#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_PCAN_GAIN_CONTROL_H_
+
+#include <stdint.h>
+#include <stdlib.h>
+
+#define kPcanSnrBits 12
+#define kPcanOutputBits 6
+
+#define kWideDynamicFunctionBits 32
+#define kWideDynamicFunctionLUTSize (4 * kWideDynamicFunctionBits - 3)
+
+struct PcanGainControlState {
+  int enable_pcan;
+  uint32_t* noise_estimate;
+  int num_channels;
+  int16_t gain_lut[kWideDynamicFunctionLUTSize];
+  int32_t snr_shift;
+};
+
+int16_t WideDynamicFunction(const uint32_t x, const int16_t* lut);
+
+uint32_t PcanShrink(const uint32_t x);
+
+void PcanGainControlApply(struct PcanGainControlState* state, uint32_t* signal);
+
+#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_PCAN_GAIN_CONTROL_H_

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/pcan_gain_control_test.cc

@@ -0,0 +1,66 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/pcan_gain_control.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/pcan_gain_control_util.h"
+
+#include "tensorflow/lite/experimental/micro/testing/micro_test.h"
+
+namespace {
+
+const int kNumChannels = 2;
+const int kSmoothingBits = 10;
+const int kCorrectionBits = -1;
+
+// Test pcan auto gain control using default config values.
+class PcanGainControlTestConfig {
+ public:
+  PcanGainControlTestConfig() {
+    config_.enable_pcan = 1;
+    config_.strength = 0.95;
+    config_.offset = 80.0;
+    config_.gain_bits = 21;
+  }
+
+  struct PcanGainControlConfig config_;
+};
+
+}  // namespace
+
+TF_LITE_MICRO_TESTS_BEGIN
+
+TF_LITE_MICRO_TEST(PcanGainControlTest_TestPcanGainControl) {
+  tflite::MicroErrorReporter micro_error_reporter;
+  tflite::ErrorReporter* error_reporter = &micro_error_reporter;
+
+  uint32_t estimate[] = {6321887, 31248341};
+  PcanGainControlTestConfig config;
+  struct PcanGainControlState state;
+  TF_LITE_MICRO_EXPECT(PcanGainControlPopulateState(
+      error_reporter, &config.config_, &state, estimate, kNumChannels,
+      kSmoothingBits, kCorrectionBits));
+
+  uint32_t signal[] = {241137, 478104};
+  PcanGainControlApply(&state, signal);
+
+  const uint32_t expected[] = {3578, 1533};
+  TF_LITE_MICRO_EXPECT_EQ(state.num_channels,
+                          sizeof(expected) / sizeof(expected[0]));
+  int i;
+  for (i = 0; i < state.num_channels; ++i) {
+    TF_LITE_MICRO_EXPECT_EQ(signal[i], expected[i]);
+  }
+}
+
+TF_LITE_MICRO_TESTS_END

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/pcan_gain_control_util.cc

@@ -0,0 +1,87 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/pcan_gain_control_util.h"
+
+#include <math.h>
+
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/static_alloc.h"
+
+#define kint16max 0x00007FFF
+
+void PcanGainControlFillConfigWithDefaults(
+    struct PcanGainControlConfig* config) {
+  config->enable_pcan = 0;
+  config->strength = 0.95;
+  config->offset = 80.0;
+  config->gain_bits = 21;
+}
+
+int16_t PcanGainLookupFunction(const struct PcanGainControlConfig* config,
+                               int32_t input_bits, uint32_t x) {
+  const float x_as_float =
+      (static_cast<float>(x)) / (static_cast<uint32_t>(1) << input_bits);
+  const float gain_as_float =
+      (static_cast<uint32_t>(1) << config->gain_bits) *
+      powf(x_as_float + config->offset, -config->strength);
+
+  if (gain_as_float > kint16max) {
+    return kint16max;
+  }
+  return static_cast<int16_t>(gain_as_float + 0.5f);
+}
+
+int PcanGainControlPopulateState(tflite::ErrorReporter* error_reporter,
+                                 const struct PcanGainControlConfig* config,
+                                 struct PcanGainControlState* state,
+                                 uint32_t* noise_estimate,
+                                 const int num_channels,
+                                 const uint16_t smoothing_bits,
+                                 const int32_t input_correction_bits) {
+  state->enable_pcan = config->enable_pcan;
+  if (!state->enable_pcan) {
+    return 1;
+  }
+  state->noise_estimate = noise_estimate;
+  state->num_channels = num_channels;
+  STATIC_ALLOC_ENSURE_ARRAY_SIZE(
+      state->gain_lut, (kWideDynamicFunctionLUTSize * sizeof(int16_t)));
+  state->snr_shift = config->gain_bits - input_correction_bits - kPcanSnrBits;
+
+  const int32_t input_bits = smoothing_bits - input_correction_bits;
+  state->gain_lut[0] = PcanGainLookupFunction(config, input_bits, 0);
+  state->gain_lut[1] = PcanGainLookupFunction(config, input_bits, 1);
+  int16_t* temp_gain_lut = state->gain_lut - 6;
+  int interval;
+  for (interval = 2; interval <= kWideDynamicFunctionBits; ++interval) {
+    const uint32_t x0 = static_cast<uint32_t>(1) << (interval - 1);
+    const uint32_t x1 = x0 + (x0 >> 1);
+    const uint32_t x2 =
+        (interval == kWideDynamicFunctionBits) ? x0 + (x0 - 1) : 2 * x0;
+
+    const int16_t y0 = PcanGainLookupFunction(config, input_bits, x0);
+    const int16_t y1 = PcanGainLookupFunction(config, input_bits, x1);
+    const int16_t y2 = PcanGainLookupFunction(config, input_bits, x2);
+
+    const int32_t diff1 = static_cast<int32_t>(y1) - y0;
+    const int32_t diff2 = static_cast<int32_t>(y2) - y0;
+    const int32_t a1 = 4 * diff1 - diff2;
+    const int32_t a2 = diff2 - a1;
+
+    temp_gain_lut[4 * interval] = y0;
+    temp_gain_lut[4 * interval + 1] = static_cast<int16_t>(a1);
+    temp_gain_lut[4 * interval + 2] = static_cast<int16_t>(a2);
+  }
+  return 1;
+}

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/pcan_gain_control_util.h

@@ -0,0 +1,47 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_PCAN_GAIN_CONTROL_UTIL_H_
+#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_PCAN_GAIN_CONTROL_UTIL_H_
+
+#include "tensorflow/lite/c/c_api_internal.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/pcan_gain_control.h"
+#include "tensorflow/lite/experimental/micro/micro_error_reporter.h"
+
+struct PcanGainControlConfig {
+  // set to false (0) to disable this module
+  int enable_pcan;
+  // gain normalization exponent (0.0 disables, 1.0 full strength)
+  float strength;
+  // positive value added in the normalization denominator
+  float offset;
+  // number of fractional bits in the gain
+  int gain_bits;
+};
+
+void PcanGainControlFillConfigWithDefaults(
+    struct PcanGainControlConfig* config);
+
+int16_t PcanGainLookupFunction(const struct PcanGainControlConfig* config,
+                               int32_t input_bits, uint32_t x);
+
+int PcanGainControlPopulateState(tflite::ErrorReporter* error_reporter,
+                                 const struct PcanGainControlConfig* config,
+                                 struct PcanGainControlState* state,
+                                 uint32_t* noise_estimate,
+                                 const int num_channels,
+                                 const uint16_t smoothing_bits,
+                                 const int32_t input_correction_bits);
+
+#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_PCAN_GAIN_CONTROL_UTIL_H_

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/static_alloc.h

@@ -0,0 +1,32 @@
+/* Copyright 2019 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+
+#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_STATIC_ALLOC_H_
+#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_STATIC_ALLOC_H_
+
+// Checks to ensure that the C-style array passed in has a compile-time size of
+// at least the number of bytes requested. This doesn't work with raw pointers
+// since sizeof() doesn't know their actual length, so only use this to check
+// statically-allocated arrays with known sizes.
+#define STATIC_ALLOC_ENSURE_ARRAY_SIZE(A, N)                                 \
+  do {                                                                       \
+    if (sizeof(A) < (N)) {                                                   \
+      error_reporter->Report(#A " too small (%d bytes, wanted %d) at %s:%d", \
+                             sizeof(A), (N), __FILE__, __LINE__);            \
+      return 0;                                                              \
+    }                                                                        \
+  } while (0)
+
+#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_STATIC_ALLOC_H_

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/tiny_conv_micro_features_model_data.h

@@ -0,0 +1,27 @@
+/* Copyright 2019 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+
+// This is a standard TensorFlow Lite model file that has been converted into a
+// C data array, so it can be easily compiled into a binary for devices that
+// don't have a file system. It was created using the command:
+// xxd -i tiny_conv.tflite > tiny_conv_simple_features_model_data.cc
+
+#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_TINY_CONV_MICRO_FEATURES_MODEL_DATA_H_
+#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_TINY_CONV_MICRO_FEATURES_MODEL_DATA_H_
+
+extern const unsigned char g_tiny_conv_micro_features_model_data[];
+extern const int g_tiny_conv_micro_features_model_data_len;
+
+#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_TINY_CONV_MICRO_FEATURES_MODEL_DATA_H_

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/window.cc

@@ -0,0 +1,70 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/window.h"
+
+#include <string.h>
+
+int WindowProcessSamples(struct WindowState* state, const int16_t* samples,
+                         size_t num_samples, size_t* num_samples_read) {
+  const int size = state->size;
+
+  // Copy samples from the samples buffer over to our local input.
+  size_t max_samples_to_copy = state->size - state->input_used;
+  if (max_samples_to_copy > num_samples) {
+    max_samples_to_copy = num_samples;
+  }
+  memcpy(state->input + state->input_used, samples,
+         max_samples_to_copy * sizeof(*samples));
+  *num_samples_read = max_samples_to_copy;
+  state->input_used += max_samples_to_copy;
+
+  if (state->input_used < state->size) {
+    // We don't have enough samples to compute a window.
+    return 0;
+  }
+
+  // Apply the window to the input.
+  const int16_t* coefficients = state->coefficients;
+  const int16_t* input = state->input;
+  int16_t* output = state->output;
+  int i;
+  int16_t max_abs_output_value = 0;
+  for (i = 0; i < size; ++i) {
+    int16_t new_value = ((static_cast<int32_t>(*input++)) * *coefficients++) >>
+                        kFrontendWindowBits;
+    *output++ = new_value;
+    if (new_value < 0) {
+      new_value = -new_value;
+    }
+    if (new_value > max_abs_output_value) {
+      max_abs_output_value = new_value;
+    }
+  }
+  // Shuffle the input down by the step size, and update how much we have used.
+  memmove(state->input, state->input + state->step,
+          sizeof(*state->input) * (state->size - state->step));
+  state->input_used -= state->step;
+  state->max_abs_output_value = max_abs_output_value;
+
+  // Indicate that the output buffer is valid for the next stage.
+  return 1;
+}
+
+void WindowReset(struct WindowState* state) {
+  memset(state->input, 0, state->size * sizeof(*state->input));
+  memset(state->output, 0, state->size * sizeof(*state->output));
+  state->input_used = 0;
+  state->max_abs_output_value = 0;
+}

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/window.h

@@ -0,0 +1,43 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_WINDOW_H_
+#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_WINDOW_H_
+
+#include <stdint.h>
+#include <stdlib.h>
+
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/micro_model_settings.h"
+
+#define kFrontendWindowBits 12
+
+struct WindowState {
+  size_t size;
+  int16_t coefficients[kMaxAudioSampleSize];
+  size_t step;
+
+  int16_t input[kMaxAudioSampleSize];
+  size_t input_used;
+  int16_t output[kMaxAudioSampleSize];
+  int16_t max_abs_output_value;
+};
+
+// Applies a window to the samples coming in, stepping forward at the given
+// rate.
+int WindowProcessSamples(struct WindowState* state, const int16_t* samples,
+                         size_t num_samples, size_t* num_samples_read);
+
+void WindowReset(struct WindowState* state);
+
+#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_WINDOW_H_

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/window_test.cc

@@ -0,0 +1,183 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/window.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/window_util.h"
+
+#include "tensorflow/lite/experimental/micro/testing/micro_test.h"
+
+namespace {
+
+const int kSampleRate = 1000;
+const int kWindowSamples = 25;
+const int kStepSamples = 10;
+const int16_t kFakeAudioData[] = {
+    0, 32767, 0, -32768, 0, 32767, 0, -32768, 0, 32767, 0, -32768,
+    0, 32767, 0, -32768, 0, 32767, 0, -32768, 0, 32767, 0, -32768,
+    0, 32767, 0, -32768, 0, 32767, 0, -32768, 0, 32767, 0, -32768};
+
+// Test window function behaviors using default config values.
+class WindowTestConfig {
+ public:
+  WindowTestConfig() {
+    config_.size_ms = 25;
+    config_.step_size_ms = 10;
+  }
+
+  struct WindowConfig config_;
+};
+
+}  // namespace
+
+TF_LITE_MICRO_TESTS_BEGIN
+
+TF_LITE_MICRO_TEST(WindowState_CheckCoefficients) {
+  tflite::MicroErrorReporter micro_error_reporter;
+  tflite::ErrorReporter* error_reporter = &micro_error_reporter;
+
+  WindowTestConfig config;
+  struct WindowState state;
+  TF_LITE_MICRO_EXPECT(WindowPopulateState(error_reporter, &config.config_,
+                                           &state, kSampleRate));
+
+  const int16_t expected[] = {16,   144,  391,  743,  1176, 1664, 2177,
+                              2681, 3145, 3541, 3843, 4032, 4096, 4032,
+                              3843, 3541, 3145, 2681, 2177, 1664, 1176,
+                              743,  391,  144,  16};
+  TF_LITE_MICRO_EXPECT_EQ(state.size, sizeof(expected) / sizeof(expected[0]));
+  int i;
+  for (i = 0; i < state.size; ++i) {
+    TF_LITE_MICRO_EXPECT_EQ(state.coefficients[i], expected[i]);
+  }
+}
+
+TF_LITE_MICRO_TEST(WindowState_CheckResidualInput) {
+  tflite::MicroErrorReporter micro_error_reporter;
+  tflite::ErrorReporter* error_reporter = &micro_error_reporter;
+
+  WindowTestConfig config;
+  struct WindowState state;
+  TF_LITE_MICRO_EXPECT(WindowPopulateState(error_reporter, &config.config_,
+                                           &state, kSampleRate));
+  size_t num_samples_read;
+
+  TF_LITE_MICRO_EXPECT(WindowProcessSamples(
+      &state, kFakeAudioData,
+      sizeof(kFakeAudioData) / sizeof(kFakeAudioData[0]), &num_samples_read));
+
+  int i;
+  for (i = kStepSamples; i < kWindowSamples; ++i) {
+    TF_LITE_MICRO_EXPECT_EQ(state.input[i - kStepSamples], kFakeAudioData[i]);
+  }
+}
+
+TF_LITE_MICRO_TEST(WindowState_CheckOutputValues) {
+  tflite::MicroErrorReporter micro_error_reporter;
+  tflite::ErrorReporter* error_reporter = &micro_error_reporter;
+
+  WindowTestConfig config;
+  struct WindowState state;
+  TF_LITE_MICRO_EXPECT(WindowPopulateState(error_reporter, &config.config_,
+                                           &state, kSampleRate));
+  size_t num_samples_read;
+
+  TF_LITE_MICRO_EXPECT(WindowProcessSamples(
+      &state, kFakeAudioData,
+      sizeof(kFakeAudioData) / sizeof(kFakeAudioData[0]), &num_samples_read));
+
+  const int16_t expected[] = {
+      0, 1151,   0, -5944, 0, 13311,  0, -21448, 0, 28327, 0, -32256, 0, 32255,
+      0, -28328, 0, 21447, 0, -13312, 0, 5943,   0, -1152, 0};
+  TF_LITE_MICRO_EXPECT_EQ(state.size, sizeof(expected) / sizeof(expected[0]));
+  int i;
+  for (i = 0; i < state.size; ++i) {
+    TF_LITE_MICRO_EXPECT_EQ(state.output[i], expected[i]);
+  }
+}
+
+TF_LITE_MICRO_TEST(WindowState_CheckMaxAbsValue) {
+  tflite::MicroErrorReporter micro_error_reporter;
+  tflite::ErrorReporter* error_reporter = &micro_error_reporter;
+
+  WindowTestConfig config;
+  struct WindowState state;
+  TF_LITE_MICRO_EXPECT(WindowPopulateState(error_reporter, &config.config_,
+                                           &state, kSampleRate));
+  size_t num_samples_read;
+
+  TF_LITE_MICRO_EXPECT(WindowProcessSamples(
+      &state, kFakeAudioData,
+      sizeof(kFakeAudioData) / sizeof(kFakeAudioData[0]), &num_samples_read));
+
+  TF_LITE_MICRO_EXPECT_EQ(state.max_abs_output_value, 32256);
+}
+
+TF_LITE_MICRO_TEST(WindowState_CheckConsecutiveWindow) {
+  tflite::MicroErrorReporter micro_error_reporter;
+  tflite::ErrorReporter* error_reporter = &micro_error_reporter;
+
+  WindowTestConfig config;
+  struct WindowState state;
+  TF_LITE_MICRO_EXPECT(WindowPopulateState(error_reporter, &config.config_,
+                                           &state, kSampleRate));
+  size_t num_samples_read;
+
+  TF_LITE_MICRO_EXPECT(WindowProcessSamples(
+      &state, kFakeAudioData,
+      sizeof(kFakeAudioData) / sizeof(kFakeAudioData[0]), &num_samples_read));
+  TF_LITE_MICRO_EXPECT(WindowProcessSamples(
+      &state, kFakeAudioData + kWindowSamples,
+      sizeof(kFakeAudioData) / sizeof(kFakeAudioData[0]) - kWindowSamples,
+      &num_samples_read));
+
+  const int16_t expected[] = {
+      0, -1152, 0, 5943,   0, -13312, 0, 21447, 0, -28328, 0, 32255, 0, -32256,
+      0, 28327, 0, -21448, 0, 13311,  0, -5944, 0, 1151,   0};
+  TF_LITE_MICRO_EXPECT_EQ(state.size, sizeof(expected) / sizeof(expected[0]));
+  int i;
+  for (i = 0; i < state.size; ++i) {
+    TF_LITE_MICRO_EXPECT_EQ(state.output[i], expected[i]);
+  }
+}
+
+TF_LITE_MICRO_TEST(WindowState_CheckNotEnoughSamples) {
+  tflite::MicroErrorReporter micro_error_reporter;
+  tflite::ErrorReporter* error_reporter = &micro_error_reporter;
+
+  WindowTestConfig config;
+  struct WindowState state;
+  TF_LITE_MICRO_EXPECT(WindowPopulateState(error_reporter, &config.config_,
+                                           &state, kSampleRate));
+  size_t num_samples_read;
+
+  TF_LITE_MICRO_EXPECT(WindowProcessSamples(
+      &state, kFakeAudioData,
+      sizeof(kFakeAudioData) / sizeof(kFakeAudioData[0]), &num_samples_read));
+  TF_LITE_MICRO_EXPECT(WindowProcessSamples(
+      &state, kFakeAudioData + kWindowSamples,
+      sizeof(kFakeAudioData) / sizeof(kFakeAudioData[0]) - kWindowSamples,
+      &num_samples_read));
+  TF_LITE_MICRO_EXPECT_EQ(
+      false, WindowProcessSamples(
+                 &state, kFakeAudioData + kWindowSamples + kStepSamples,
+                 sizeof(kFakeAudioData) / sizeof(kFakeAudioData[0]) -
+                     kWindowSamples - kStepSamples,
+                 &num_samples_read));
+
+  TF_LITE_MICRO_EXPECT_EQ(
+      state.input_used,
+      sizeof(kFakeAudioData) / sizeof(kFakeAudioData[0]) - 2 * kStepSamples);
+}
+
+TF_LITE_MICRO_TESTS_END

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/window_util.cc

@@ -0,0 +1,57 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/window_util.h"
+
+#include <math.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/static_alloc.h"
+
+// Needed because some platforms don't have M_PI defined.
+#define WINDOW_PI (3.14159265358979323846f)
+
+void WindowFillConfigWithDefaults(struct WindowConfig* config) {
+  config->size_ms = 25;
+  config->step_size_ms = 10;
+}
+
+int WindowPopulateState(tflite::ErrorReporter* error_reporter,
+                        const struct WindowConfig* config,
+                        struct WindowState* state, int sample_rate) {
+  state->size = config->size_ms * sample_rate / 1000;
+  state->step = config->step_size_ms * sample_rate / 1000;
+
+  STATIC_ALLOC_ENSURE_ARRAY_SIZE(state->coefficients,
+                                 (state->size * sizeof(*state->coefficients)));
+
+  // Populate the window values.
+  const float arg = WINDOW_PI * 2.0 / (static_cast<float>(state->size));
+  int i;
+  for (i = 0; i < state->size; ++i) {
+    float float_value = 0.5 - (0.5 * cos(arg * (i + 0.5)));
+    // Scale it to fixed point and round it.
+    state->coefficients[i] =
+        floor(float_value * (1 << kFrontendWindowBits) + 0.5);
+  }
+
+  state->input_used = 0;
+  STATIC_ALLOC_ENSURE_ARRAY_SIZE(state->input,
+                                 (state->size * sizeof(*state->input)));
+
+  STATIC_ALLOC_ENSURE_ARRAY_SIZE(state->output,
+                                 (state->size * sizeof(*state->output)));
+  return 1;
+}

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/window_util.h

@@ -0,0 +1,40 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_WINDOW_UTIL_H_
+#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_WINDOW_UTIL_H_
+
+#include "tensorflow/lite/c/c_api_internal.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/window.h"
+#include "tensorflow/lite/experimental/micro/micro_error_reporter.h"
+
+struct WindowConfig {
+  // length of window frame in milliseconds
+  size_t size_ms;
+  // length of step for next frame in milliseconds
+  size_t step_size_ms;
+};
+
+// Populates the WindowConfig with "sane" default values.
+void WindowFillConfigWithDefaults(struct WindowConfig* config);
+
+// Allocates any buffers.
+int WindowPopulateState(tflite::ErrorReporter* error_reporter,
+                        const struct WindowConfig* config,
+                        struct WindowState* state, int sample_rate);
+
+// Frees any allocated buffers.
+void WindowFreeStateContents(struct WindowState* state);
+
+#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_WINDOW_UTIL_H_

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/yes_feature_data_slice.cc

@@ -0,0 +1,24 @@
+/* Copyright 2019 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+
+// See the header for documentation on the meaning of this data.
+
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/yes_feature_data_slice.h"
+
+const uint8_t g_yes_feature_data_slice[g_yes_feature_data_slice_size] = {
+    214, 215, 236, 202, 235, 203, 225, 191, 203, 188, 199, 194, 212, 127,
+    51,  0,   174, 188, 219, 196, 228, 221, 240, 207, 235, 220, 241, 219,
+    237, 207, 212, 142, 95,  0,   139, 78,  162, 177, 197, 183,
+};

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/yes_feature_data_slice.h

@@ -0,0 +1,29 @@
+/* Copyright 2019 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+
+// This data was extracted from the larger feature data held in
+// no_micro_features_data.cc and consists of the 26th spectrogram slice of 40
+// values. This is the expected result of running the sample data in
+// yes_30ms_sample_data.cc through through the preprocessing pipeline.
+
+#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_YES_FEATURE_DATA_SLICE_H_
+#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_YES_FEATURE_DATA_SLICE_H_
+
+#include <cstdint>
+
+constexpr int g_yes_feature_data_slice_size = 40;
+extern const uint8_t g_yes_feature_data_slice[];
+
+#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_YES_FEATURE_DATA_SLICE_H_

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/yes_micro_features_data.cc

@@ -0,0 +1,165 @@
+/* Copyright 2019 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/yes_micro_features_data.h"
+
+/* File automatically created by
+ * tensorflow/examples/speech_commands/wav_to_features.py \
+ * --sample_rate=16000 \
+ * --clip_duration_ms=1000 \
+ * --window_size_ms=30 \
+ * --window_stride_ms=20 \
+ * --feature_bin_count=40 \
+ * --quantize=1 \
+ * --preprocess="micro" \
+ * --input_wav="speech_commands_test_set_v0.02/yes/f2e59fea_nohash_1.wav" \
+ * --output_c_file="yes_micro_features_data.cc" \
+ */
+
+const int g_yes_micro_f2e59fea_nohash_1_width = 40;
+const int g_yes_micro_f2e59fea_nohash_1_height = 49;
+const unsigned char g_yes_micro_f2e59fea_nohash_1_data[] = {
+    244, 226, 245, 223, 234, 213, 228, 208, 194, 110, 95,  116, 102, 0,   137,
+    161, 183, 173, 137, 116, 133, 157, 151, 156, 128, 110, 128, 0,   68,  78,
+    78,  90,  68,  68,  78,  102, 95,  78,  95,  78,  210, 188, 209, 183, 204,
+    188, 201, 191, 166, 119, 90,  107, 110, 107, 175, 157, 179, 168, 182, 145,
+    152, 164, 171, 165, 136, 143, 122, 68,  0,   78,  90,  90,  110, 90,  102,
+    99,  90,  68,  78,  68,  223, 186, 179, 123, 182, 110, 196, 171, 159, 110,
+    102, 95,  90,  99,  160, 134, 125, 136, 153, 152, 164, 134, 164, 151, 141,
+    136, 99,  90,  90,  90,  78,  78,  102, 119, 102, 90,  110, 90,  68,  51,
+    177, 175, 211, 172, 183, 0,   95,  68,  129, 102, 68,  85,  114, 105, 110,
+    85,  102, 95,  140, 51,  85,  51,  95,  90,  143, 116, 90,  78,  78,  51,
+    107, 85,  68,  0,   68,  51,  90,  51,  68,  0,   164, 117, 193, 120, 156,
+    0,   138, 51,  90,  0,   51,  0,   51,  85,  0,   0,   51,  0,   0,   0,
+    0,   0,   114, 0,   85,  78,  90,  51,  0,   0,   51,  85,  99,  85,  107,
+    68,  90,  85,  78,  0,   51,  0,   110, 0,   68,  0,   0,   0,   51,  0,
+    51,  0,   0,   0,   68,  90,  107, 0,   68,  0,   0,   0,   68,  0,   51,
+    68,  0,   78,  68,  0,   51,  0,   78,  68,  90,  68,  78,  51,  51,  0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   90,  0,   0,   0,   0,
+    0,   51,  0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   51,  68,
+    0,   0,   78,  0,   78,  0,   78,  0,   51,  0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   51,  0,   51,  0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   51,  0,   51,
+    0,   51,  0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   51,
+    0,   0,   0,   0,   51,  78,  0,   0,   51,  51,  0,   0,   0,   78,  0,
+    213, 170, 192, 180, 196, 188, 173, 131, 173, 116, 137, 105, 159, 127, 0,
+    0,   0,   0,   127, 164, 165, 161, 170, 164, 185, 197, 195, 167, 134, 138,
+    159, 134, 136, 105, 51,  0,   99,  0,   51,  0,   228, 215, 229, 218, 237,
+    215, 228, 210, 237, 222, 239, 211, 208, 211, 234, 218, 220, 209, 225, 219,
+    235, 222, 245, 225, 245, 224, 243, 223, 241, 218, 237, 224, 234, 213, 221,
+    193, 197, 164, 157, 128, 227, 188, 232, 196, 220, 220, 240, 219, 234, 213,
+    234, 211, 231, 218, 233, 213, 239, 215, 228, 207, 229, 206, 224, 208, 226,
+    207, 232, 210, 225, 208, 230, 199, 227, 206, 210, 205, 218, 174, 178, 141,
+    235, 208, 220, 206, 225, 203, 233, 203, 225, 167, 205, 199, 208, 190, 221,
+    204, 223, 207, 225, 188, 225, 197, 215, 188, 199, 183, 225, 195, 224, 200,
+    216, 178, 208, 188, 215, 202, 214, 183, 176, 140, 198, 150, 211, 194, 203,
+    120, 175, 188, 204, 189, 219, 192, 223, 202, 216, 186, 203, 185, 210, 182,
+    214, 183, 204, 170, 204, 125, 184, 187, 206, 185, 198, 182, 210, 161, 202,
+    198, 218, 173, 145, 120, 188, 183, 205, 168, 200, 170, 210, 177, 187, 190,
+    209, 193, 193, 166, 210, 162, 175, 119, 174, 147, 182, 161, 181, 134, 176,
+    143, 187, 165, 186, 149, 185, 141, 192, 181, 202, 123, 170, 143, 144, 78,
+    149, 0,   208, 182, 170, 78,  170, 0,   117, 51,  156, 99,  195, 170, 200,
+    130, 152, 68,  175, 141, 173, 134, 194, 132, 189, 164, 198, 134, 173, 117,
+    171, 149, 183, 181, 185, 99,  153, 117, 125, 0,   166, 0,   173, 117, 144,
+    0,   117, 102, 188, 120, 193, 166, 197, 68,  163, 119, 169, 99,  134, 0,
+    162, 0,   164, 68,  171, 116, 126, 0,   120, 68,  68,  0,   105, 0,   159,
+    95,  150, 51,  90,  85,  0,   0,   131, 0,   105, 0,   145, 51,  170, 51,
+    120, 0,   107, 0,   145, 85,  160, 0,   85,  0,   0,   51,  149, 0,   78,
+    0,   0,   0,   0,   0,   0,   0,   90,  0,   112, 0,   78,  102, 122, 0,
+    0,   0,   0,   0,   105, 0,   0,   0,   0,   0,   0,   0,   0,   0,   112,
+    0,   164, 120, 143, 0,   0,   0,   0,   0,   51,  0,   90,  0,   78,  0,
+    0,   0,   0,   0,   110, 0,   139, 0,   112, 51,  0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   102, 0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   107,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   78,  0,   51,  0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   51,  0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   127, 110, 133, 0,   167, 0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   132, 0,   190,
+    194, 202, 0,   197, 187, 161, 0,   0,   0,   0,   0,   0,   0,   0,   0,
+    214, 213, 223, 203, 218, 189, 200, 122, 78,  0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   191, 210, 231, 197, 226, 217, 238, 216, 236, 207,
+    199, 0,   0,   0,   0,   0,   107, 122, 155, 160, 214, 215, 236, 202, 235,
+    203, 225, 191, 203, 188, 199, 194, 212, 127, 51,  0,   174, 188, 219, 196,
+    228, 221, 240, 207, 235, 220, 241, 219, 237, 207, 212, 142, 95,  0,   139,
+    78,  162, 177, 197, 183, 211, 199, 235, 208, 238, 215, 227, 207, 211, 201,
+    224, 213, 226, 192, 213, 170, 223, 205, 234, 221, 245, 225, 242, 220, 245,
+    221, 239, 221, 238, 213, 226, 180, 159, 112, 176, 159, 208, 202, 213, 191,
+    205, 191, 225, 197, 238, 219, 224, 201, 227, 200, 221, 201, 225, 203, 212,
+    195, 229, 210, 228, 210, 239, 216, 226, 212, 233, 205, 225, 200, 229, 207,
+    222, 151, 147, 119, 179, 185, 230, 218, 223, 192, 202, 136, 205, 177, 223,
+    204, 228, 215, 232, 209, 221, 189, 221, 205, 209, 200, 226, 209, 229, 205,
+    235, 192, 209, 198, 228, 190, 206, 185, 207, 187, 214, 175, 177, 184, 220,
+    195, 214, 207, 230, 184, 205, 159, 208, 184, 189, 169, 224, 213, 219, 199,
+    229, 203, 216, 205, 222, 204, 224, 206, 231, 208, 231, 176, 197, 184, 216,
+    193, 211, 139, 212, 195, 231, 164, 166, 195, 217, 182, 208, 190, 217, 179,
+    205, 68,  182, 119, 195, 168, 182, 136, 204, 179, 193, 158, 182, 140, 188,
+    154, 197, 169, 190, 99,  184, 0,   125, 0,   131, 0,   99,  68,  179, 85,
+    190, 184, 213, 203, 223, 202, 212, 190, 209, 138, 178, 0,   159, 51,  128,
+    51,  105, 0,   139, 51,  179, 125, 185, 114, 171, 128, 175, 132, 181, 174,
+    155, 0,   0,   0,   90,  0,   125, 0,   176, 188, 227, 217, 244, 215, 234,
+    221, 239, 192, 224, 210, 0,   0,   134, 0,   51,  0,   105, 0,   105, 0,
+    143, 90,  192, 119, 175, 147, 141, 51,  184, 110, 85,  0,   0,   0,   0,
+    0,   0,   0,   151, 139, 201, 203, 232, 203, 226, 208, 236, 206, 230, 212,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   169, 0,   119,
+    0,   78,  0,   0,   0,   0,   0,   0,   0,   0,   0,   68,  0,   0,   133,
+    200, 180, 220, 197, 228, 201, 221, 184, 213, 193, 110, 0,   0,   0,   0,
+    0,   0,   0,   0,   0,   78,  0,   164, 0,   0,   0,   0,   0,   107, 0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   150, 164, 202, 182, 224,
+    197, 211, 179, 212, 193, 134, 0,   0,   0,   0,   0,   0,   0,   0,   0,
+    85,  0,   150, 0,   85,  0,   95,  0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   102, 90,  193, 160, 203, 164, 200, 178, 205, 174,
+    116, 0,   0,   0,   0,   0,   0,   0,   0,   0,   120, 114, 123, 0,   114,
+    0,   145, 68,  0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    102, 68,  199, 170, 195, 180, 208, 176, 200, 164, 0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   110, 0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   142, 102, 172, 110, 186,
+    167, 185, 147, 189, 154, 0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   177, 0,   158, 136, 197, 155, 189, 166,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    85,  0,   155, 90,  175, 117, 175, 138, 202, 165, 0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   51,  0,   139,
+    0,   120, 68,  51,  123, 0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   119, 0,   78,  0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+};

tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/yes_micro_features_data.h

@@ -0,0 +1,23 @@
+/* Copyright 2019 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+
+#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_YES_MICRO_FEATURES_DATA_H_
+#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_YES_MICRO_FEATURES_DATA_H_
+
+extern const int g_yes_micro_f2e59fea_nohash_1_width;
+extern const int g_yes_micro_f2e59fea_nohash_1_height;
+extern const unsigned char g_yes_micro_f2e59fea_nohash_1_data[];
+
+#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MICRO_FEATURES_YES_MICRO_FEATURES_DATA_H_

tensorflow/lite/experimental/micro/examples/micro_speech/micro_speech_test.cc

@@ -13,9 +13,9 @@ See the License for the specific language governing permissions and
 limitations under the License.
 ==============================================================================*/
 
-#include "tensorflow/lite/experimental/micro/examples/micro_speech/no_features_data.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/no_micro_features_data.h"
-#include "tensorflow/lite/experimental/micro/examples/micro_speech/tiny_conv_model_data.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/tiny_conv_micro_features_model_data.h"
-#include "tensorflow/lite/experimental/micro/examples/micro_speech/yes_features_data.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/yes_micro_features_data.h"
 #include "tensorflow/lite/experimental/micro/kernels/all_ops_resolver.h"
 #include "tensorflow/lite/experimental/micro/micro_error_reporter.h"
 #include "tensorflow/lite/experimental/micro/micro_interpreter.h"
@@ -32,7 +32,8 @@ TF_LITE_MICRO_TEST(TestInvoke) {
 
   // Map the model into a usable data structure. This doesn't involve any
   // copying or parsing, it's a very lightweight operation.
-  const tflite::Model* model = ::tflite::GetModel(g_tiny_conv_model_data);
+  const tflite::Model* model =
+      ::tflite::GetModel(g_tiny_conv_micro_features_model_data);
   if (model->version() != TFLITE_SCHEMA_VERSION) {
     error_reporter->Report(
         "Model provided is schema version %d not equal "
@@ -61,12 +62,12 @@ TF_LITE_MICRO_TEST(TestInvoke) {
   TF_LITE_MICRO_EXPECT_EQ(4, input->dims->size);
   TF_LITE_MICRO_EXPECT_EQ(1, input->dims->data[0]);
   TF_LITE_MICRO_EXPECT_EQ(49, input->dims->data[1]);
-  TF_LITE_MICRO_EXPECT_EQ(43, input->dims->data[2]);
+  TF_LITE_MICRO_EXPECT_EQ(40, input->dims->data[2]);
   TF_LITE_MICRO_EXPECT_EQ(kTfLiteUInt8, input->type);
 
   // Copy a spectrogram created from a .wav audio file of someone saying "Yes",
   // into the memory area used for the input.
-  const uint8_t* yes_features_data = g_yes_f2e59fea_nohash_1_data;
+  const uint8_t* yes_features_data = g_yes_micro_f2e59fea_nohash_1_data;
   for (int i = 0; i < input->bytes; ++i) {
     input->data.uint8[i] = yes_features_data[i];
   }
@@ -102,7 +103,7 @@ TF_LITE_MICRO_TEST(TestInvoke) {
   TF_LITE_MICRO_EXPECT_GT(yes_score, no_score);
 
   // Now test with a different input, from a recording of "No".
-  const uint8_t* no_features_data = g_no_f9643d42_nohash_4_data;
+  const uint8_t* no_features_data = g_no_micro_f9643d42_nohash_4_data;
   for (int i = 0; i < input->bytes; ++i) {
     input->data.uint8[i] = no_features_data[i];
   }

tensorflow/lite/experimental/micro/examples/micro_speech/no_1000ms_sample_data.h

@@ -0,0 +1,29 @@
+/* Copyright 2019 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+
+// This data was created from the PCM data in a WAV file held in v2 of the
+// Speech Commands test dataset, at the path:
+// speech_commands_test_set_v0.02/no/f9643d42_nohash_4.wav
+// This should contain all 16,000 samples from the one-second file.
+
+#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_NO_1000MS_SAMPLE_DATA_H_
+#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_NO_1000MS_SAMPLE_DATA_H_
+
+#include <cstdint>
+
+extern const int g_no_1000ms_sample_data_size;
+extern const int16_t g_no_1000ms_sample_data[];
+
+#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_NO_1000MS_SAMPLE_DATA_H_

tensorflow/lite/experimental/micro/examples/micro_speech/osx/audio_provider.cc

@@ -17,7 +17,7 @@ limitations under the License.
 
 #include <AudioToolbox/AudioToolbox.h>
 
-#include "tensorflow/lite/experimental/micro/examples/micro_speech/model_settings.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/simple_model_settings.h"
 
 namespace {
 

tensorflow/lite/experimental/micro/examples/micro_speech/recognize_commands.cc

@@ -28,7 +28,7 @@ RecognizeCommands::RecognizeCommands(tflite::ErrorReporter* error_reporter,
       suppression_ms_(suppression_ms),
       minimum_count_(minimum_count),
       previous_results_(error_reporter) {
-  previous_top_label_ = "_silence_";
+  previous_top_label_ = "silence";
   previous_top_label_time_ = 0;
 }
 

tensorflow/lite/experimental/micro/examples/micro_speech/recognize_commands.h

@@ -19,7 +19,7 @@ limitations under the License.
 #include <cstdint>
 
 #include "tensorflow/lite/c/c_api_internal.h"
-#include "tensorflow/lite/experimental/micro/examples/micro_speech/model_settings.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/micro_features/micro_model_settings.h"
 #include "tensorflow/lite/experimental/micro/micro_error_reporter.h"
 
 // Partial implementation of std::dequeue, just providing the functionality
@@ -129,8 +129,8 @@ class RecognizeCommands {
   // help reduce spurious recognitions.
   explicit RecognizeCommands(tflite::ErrorReporter* error_reporter,
                              int32_t average_window_duration_ms = 1000,
-                             uint8_t detection_threshold = 51,
+                             uint8_t detection_threshold = 200,
-                             int32_t suppression_ms = 500,
+                             int32_t suppression_ms = 1500,
                              int32_t minimum_count = 3);
 
   // Call this with the results of running a model on sample data.

tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/CMSIS/simple_features_generator.cc

@@ -13,6 +13,8 @@ See the License for the specific language governing permissions and
 limitations under the License.
 ==============================================================================*/
 
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/simple_features_generator.h"
+
 extern "C" {
 #define IFFT_FLAG_R 0
 #define BIT_REVERSE_FLAG 1
@@ -23,8 +25,6 @@ extern "C" {
 #include "tensorflow/lite/experimental/micro/examples/micro_speech/CMSIS/hanning.h"
 }
 
-#include "tensorflow/lite/experimental/micro/examples/micro_speech/preprocessor.h"
-
 void quantize(q15_t* bufA, q15_t* bufB, uint8_t* output);
 
 q15_t bufA[FFT_SIZE];
@@ -41,9 +41,9 @@ constexpr int kOutputSize =
     ((kInputSize / 2) + (kAverageWindowSize - 1)) / kAverageWindowSize;
 }  // namespace
 
-TfLiteStatus Preprocess(tflite::ErrorReporter* error_reporter,
+TfLiteStatus GenerateSimpleFeatures(tflite::ErrorReporter* error_reporter,
-                        const int16_t* input, int input_size, int output_size,
+                                    const int16_t* input, int input_size,
-                        uint8_t* output) {
+                                    int output_size, uint8_t* output) {
   if (input_size > kInputSize) {
     error_reporter->Report("Input size %d larger than %d", input_size,
                            kInputSize);
@@ -93,12 +93,3 @@ void quantize(q15_t* bufA, q15_t* bufB, uint8_t* output) {
     output[i] = (uint8_t)(bufA[i] >> 5);
   }
 }
-
-TfLiteStatus Preprocess_1sec(tflite::ErrorReporter* error_reporter,
-                             const int16_t* input, uint8_t* output) {
-  int i;
-  for (i = 0; i < 49; i++) {
-    Preprocess(error_reporter, input + i * 320, 480, 43, output + i * 43);
-  }
-  return kTfLiteOk;
-}

tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/fixed_point/simple_features_generator.cc

@@ -27,11 +27,11 @@ limitations under the License.
 // instead of floating point, to help show how this can work on platforms that
 // don't have good float support.
 
-#include "tensorflow/lite/experimental/micro/examples/micro_speech/preprocessor.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/simple_features_generator.h"
 
 #include <cmath>
 
-#include "tensorflow/lite/experimental/micro/examples/micro_speech/model_settings.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/simple_model_settings.h"
 
 namespace {
 
@@ -118,9 +118,9 @@ void CalculatePeriodicHann(int window_length, int16_t* window_function) {
 
 }  // namespace
 
-TfLiteStatus Preprocess(tflite::ErrorReporter* error_reporter,
+TfLiteStatus GenerateSimpleFeatures(tflite::ErrorReporter* error_reporter,
-                        const int16_t* input, int input_size, int output_size,
+                                    const int16_t* input, int input_size,
-                        uint8_t* output) {
+                                    int output_size, uint8_t* output) {
   // Ensure our input and output data arrays are valid.
   if (input_size > kMaxAudioSampleSize) {
     error_reporter->Report("Input size %d larger than %d", input_size,

tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/no_power_spectrum_data.cc

@@ -15,7 +15,7 @@ limitations under the License.
 
 // See the header for documentation on the meaning of this data.
 
-#include "tensorflow/lite/experimental/micro/examples/micro_speech/no_power_spectrum_data.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/no_power_spectrum_data.h"
 
 const uint8_t g_no_power_spectrum_data[g_no_power_spectrum_data_size] = {
     255, 7, 6, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/no_power_spectrum_data.h

@@ -18,12 +18,12 @@ limitations under the License.
 // This is the expected result of running the sample data in
 // no_30ms_sample_data.cc through through the preprocessing pipeline.
 
-#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_NO_POWER_SPECTRUM_DATA_H_
+#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_SIMPLE_FEATURES_NO_POWER_SPECTRUM_DATA_H_
-#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_NO_POWER_SPECTRUM_DATA_H_
+#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_SIMPLE_FEATURES_NO_POWER_SPECTRUM_DATA_H_
 
 #include <cstdint>
 
 constexpr int g_no_power_spectrum_data_size = 43;
 extern const uint8_t g_no_power_spectrum_data[];
 
-#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_NO_POWER_SPECTRUM_DATA_H_
+#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_SIMPLE_FEATURES_NO_POWER_SPECTRUM_DATA_H_

tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/no_simple_features_data.cc

@@ -13,7 +13,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 ==============================================================================*/
 
-#include "tensorflow/lite/experimental/micro/examples/micro_speech/no_features_data.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/no_simple_features_data.h"
 
 /* File automatically created by
  * tensorflow/examples/speech_commands/wav_to_features.py \
@@ -22,15 +22,15 @@ limitations under the License.
  * --window_size_ms=30 \
  * --window_stride_ms=20 \
  * --feature_bin_count=40 \
- * --quantize \
+ * --quantize=1 \
  * --preprocess="average" \
  * --input_wav="speech_commands_test_set_v0.02/no/f9643d42_nohash_4.wav" \
- * --output_c_file="no_features_data.cc" \
+ * --output_c_file="no_simple_features_data.cc" \
  */
 
-const int g_no_f9643d42_nohash_4_width = 43;
+const int g_no_simple_f9643d42_nohash_4_width = 43;
-const int g_no_f9643d42_nohash_4_height = 49;
+const int g_no_simple_f9643d42_nohash_4_height = 49;
-const unsigned char g_no_f9643d42_nohash_4_data[] = {
+const unsigned char g_no_simple_f9643d42_nohash_4_data[] = {
     0, 0,   0,   0,  0, 0,   0,  0,  0,   0,   0,  0, 0,   0,   0,  0,  0,   0,
     0, 0,   0,   0,  0, 0,   0,  0,  0,   0,   0,  0, 0,   0,   0,  0,  0,   0,
     0, 0,   0,   0,  0, 0,   0,  0,  0,   0,   0,  0, 0,   0,   0,  0,  0,   0,

tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/no_simple_features_data.h

@@ -13,11 +13,11 @@ See the License for the specific language governing permissions and
 limitations under the License.
 ==============================================================================*/
 
-#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_NO_FEATURES_DATA_H_
+#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_SIMPLE_FEATURES_NO_SIMPLE_FEATURES_DATA_H_
-#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_NO_FEATURES_DATA_H_
+#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_SIMPLE_FEATURES_NO_SIMPLE_FEATURES_DATA_H_
 
-extern const int g_no_f9643d42_nohash_4_width;
+extern const int g_no_simple_f9643d42_nohash_4_width;
-extern const int g_no_f9643d42_nohash_4_height;
+extern const int g_no_simple_f9643d42_nohash_4_height;
-extern const unsigned char g_no_f9643d42_nohash_4_data[];
+extern const unsigned char g_no_simple_f9643d42_nohash_4_data[];
 
-#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_NO_FEATURES_DATA_H_
+#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_SIMPLE_FEATURES_NO_SIMPLE_FEATURES_DATA_H_

tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/simple_features_generator.cc

@@ -24,11 +24,11 @@ limitations under the License.
 // functions used here, for example replacing the DFT with an FFT, so this
 // version shouldn't be used where performance is critical.
 
-#include "tensorflow/lite/experimental/micro/examples/micro_speech/preprocessor.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/simple_features_generator.h"
 
 #include <cmath>
 
-#include "tensorflow/lite/experimental/micro/examples/micro_speech/model_settings.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/simple_model_settings.h"
 
 namespace {
 
@@ -72,9 +72,9 @@ void CalculatePeriodicHann(int window_length, float* window_function) {
 
 }  // namespace
 
-TfLiteStatus Preprocess(tflite::ErrorReporter* error_reporter,
+TfLiteStatus GenerateSimpleFeatures(tflite::ErrorReporter* error_reporter,
-                        const int16_t* input, int input_size, int output_size,
+                                    const int16_t* input, int input_size,
-                        uint8_t* output) {
+                                    int output_size, uint8_t* output) {
   // Ensure our input and output data arrays are valid.
   if (input_size > kMaxAudioSampleSize) {
     error_reporter->Report("Input size %d larger than %d", input_size,
@@ -146,12 +146,3 @@ TfLiteStatus Preprocess(tflite::ErrorReporter* error_reporter,
   }
   return kTfLiteOk;
 }
-
-TfLiteStatus Preprocess_1sec(tflite::ErrorReporter* error_reporter,
-                             const int16_t* input, uint8_t* output) {
-  int i;
-  for (i = 0; i < 49; i++) {
-    Preprocess(error_reporter, input + i * 320, 480, 43, output + i * 43);
-  }
-  return kTfLiteOk;
-}

tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/simple_features_generator.h

@@ -13,8 +13,8 @@ See the License for the specific language governing permissions and
 limitations under the License.
 ==============================================================================*/
 
-#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_PREPROCESSOR_H_
+#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_SIMPLE_FEATURES_SIMPLE_FEATURES_GENERATOR_H_
-#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_PREPROCESSOR_H_
+#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_SIMPLE_FEATURES_SIMPLE_FEATURES_GENERATOR_H_
 
 #include "tensorflow/lite/c/c_api_internal.h"
 #include "tensorflow/lite/experimental/micro/micro_error_reporter.h"
@@ -24,11 +24,8 @@ limitations under the License.
 // both floating point and fixed point available, but because the calculations
 // involved can be time-consuming, it's recommended that you use or write
 // specialized versions for your platform.
-TfLiteStatus Preprocess(tflite::ErrorReporter* error_reporter,
+TfLiteStatus GenerateSimpleFeatures(tflite::ErrorReporter* error_reporter,
-                        const int16_t* input, int input_size, int output_size,
+                                    const int16_t* input, int input_size,
-                        uint8_t* output);
+                                    int output_size, uint8_t* output);
 
-TfLiteStatus Preprocess_1sec(tflite::ErrorReporter* error_reporter,
+#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_SIMPLE_FEATURES_SIMPLE_FEATURES_GENERATOR_H_
-                             const int16_t* input, uint8_t* output);
-
-#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_PREPROCESSOR_H_

tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/simple_features_generator_test.cc

@@ -13,23 +13,23 @@ See the License for the specific language governing permissions and
 limitations under the License.
 ==============================================================================*/
 
-#include "tensorflow/lite/experimental/micro/examples/micro_speech/preprocessor.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/simple_features_generator.h"
 #include "tensorflow/lite/c/c_api_internal.h"
 #include "tensorflow/lite/experimental/micro/examples/micro_speech/no_30ms_sample_data.h"
-#include "tensorflow/lite/experimental/micro/examples/micro_speech/no_power_spectrum_data.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/no_power_spectrum_data.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/yes_power_spectrum_data.h"
 #include "tensorflow/lite/experimental/micro/examples/micro_speech/yes_30ms_sample_data.h"
-#include "tensorflow/lite/experimental/micro/examples/micro_speech/yes_power_spectrum_data.h"
 #include "tensorflow/lite/experimental/micro/micro_error_reporter.h"
 #include "tensorflow/lite/experimental/micro/testing/micro_test.h"
 
 TF_LITE_MICRO_TESTS_BEGIN
 
-TF_LITE_MICRO_TEST(TestPreprocessor) {
+TF_LITE_MICRO_TEST(TestSimpleFeaturesGenerator) {
   tflite::MicroErrorReporter micro_error_reporter;
   tflite::ErrorReporter* error_reporter = &micro_error_reporter;
 
   uint8_t yes_calculated_data[g_yes_power_spectrum_data_size];
-  TfLiteStatus yes_status = Preprocess(
+  TfLiteStatus yes_status = GenerateSimpleFeatures(
       error_reporter, g_yes_30ms_sample_data, g_yes_30ms_sample_data_size,
       g_yes_power_spectrum_data_size, yes_calculated_data);
   TF_LITE_MICRO_EXPECT_EQ(kTfLiteOk, yes_status);
@@ -45,7 +45,7 @@ TF_LITE_MICRO_TEST(TestPreprocessor) {
   }
 
   uint8_t no_calculated_data[g_yes_power_spectrum_data_size];
-  TfLiteStatus no_status = Preprocess(
+  TfLiteStatus no_status = GenerateSimpleFeatures(
       error_reporter, g_no_30ms_sample_data, g_no_30ms_sample_data_size,
       g_no_power_spectrum_data_size, no_calculated_data);
   TF_LITE_MICRO_EXPECT_EQ(kTfLiteOk, no_status);

tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/simple_model_settings.cc

@@ -0,0 +1,23 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/simple_model_settings.h"
+
+const char* kCategoryLabels[kCategoryCount] = {
+    "silence",
+    "unknown",
+    "yes",
+    "no",
+};

tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/simple_model_settings.h

@@ -13,8 +13,8 @@ See the License for the specific language governing permissions and
 limitations under the License.
 ==============================================================================*/
 
-#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MODEL_SETTINGS_H_
+#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_SIMPLE_FEATURES_SIMPLE_MODEL_SETTINGS_H_
-#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MODEL_SETTINGS_H_
+#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_SIMPLE_FEATURES_SIMPLE_MODEL_SETTINGS_H_
 
 // Keeping these as constant expressions allow us to allocate fixed-sized arrays
 // on the stack for our working memory.
@@ -40,4 +40,4 @@ constexpr int kSilenceIndex = 0;
 constexpr int kUnknownIndex = 1;
 extern const char* kCategoryLabels[kCategoryCount];
 
-#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_MODEL_SETTINGS_H_
+#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_SIMPLE_FEATURES_SIMPLE_MODEL_SETTINGS_H_

tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/tiny_conv_simple_features_model_data.cc

@@ -14,12 +14,12 @@ limitations under the License.
 ==============================================================================*/
 
 // Automatically created from a TensorFlow Lite flatbuffer using the command:
-// xxd -i tiny_conv.tflite > tiny_conv_model_data.cc
+// xxd -i tiny_conv.tflite > tiny_conv_simple_features_model_data.cc
 // See the README for a full description of the creation process.
 
-#include "tensorflow/lite/experimental/micro/examples/micro_speech/tiny_conv_model_data.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/tiny_conv_simple_features_model_data.h"
 
-const unsigned char g_tiny_conv_model_data[] = {
+const unsigned char g_tiny_conv_simple_features_model_data[] = {
     0x18, 0x00, 0x00, 0x00, 0x54, 0x46, 0x4c, 0x33, 0x00, 0x00, 0x0e, 0x00,
     0x18, 0x00, 0x04, 0x00, 0x08, 0x00, 0x0c, 0x00, 0x10, 0x00, 0x14, 0x00,
     0x0e, 0x00, 0x00, 0x00, 0x03, 0x00, 0x00, 0x00, 0x08, 0x4d, 0x00, 0x00,
@@ -1670,4 +1670,4 @@ const unsigned char g_tiny_conv_model_data[] = {
     0x04, 0x00, 0x00, 0x00, 0xfa, 0xff, 0xff, 0xff, 0x00, 0x19, 0x06, 0x00,
     0x06, 0x00, 0x05, 0x00, 0x06, 0x00, 0x00, 0x00, 0x00, 0x09, 0x06, 0x00,
     0x08, 0x00, 0x07, 0x00, 0x06, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04};
-const int g_tiny_conv_model_data_len = 19800;
+const int g_tiny_conv_simple_features_model_data_len = 19800;

tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/tiny_conv_simple_features_model_data.h

@@ -16,12 +16,12 @@ limitations under the License.
 // This is a standard TensorFlow Lite model file that has been converted into a
 // C data array, so it can be easily compiled into a binary for devices that
 // don't have a file system. It was created using the command:
-// xxd -i tiny_conv.tflite > tiny_conv_model_data.cc
+// xxd -i tiny_conv.tflite > tiny_conv_simple_features_model_data.cc
 
-#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_TINY_CONV_MODEL_DATA_H_
+#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_SIMPLE_FEATURES_TINY_CONV_SIMPLE_FEATURES_MODEL_DATA_H_
-#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_TINY_CONV_MODEL_DATA_H_
+#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_SIMPLE_FEATURES_TINY_CONV_SIMPLE_FEATURES_MODEL_DATA_H_
 
-extern const unsigned char g_tiny_conv_model_data[];
+extern const unsigned char g_tiny_conv_simple_features_model_data[];
-extern const int g_tiny_conv_model_data_len;
+extern const int g_tiny_conv_simple_features_model_data_len;
 
-#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_TINY_CONV_MODEL_DATA_H_
+#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_SIMPLE_FEATURES_TINY_CONV_SIMPLE_FEATURES_MODEL_DATA_H_

tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/yes_power_spectrum_data.cc

@@ -15,7 +15,7 @@ limitations under the License.
 
 // See the header for documentation on the meaning of this data.
 
-#include "tensorflow/lite/experimental/micro/examples/micro_speech/yes_power_spectrum_data.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/yes_power_spectrum_data.h"
 
 const uint8_t g_yes_power_spectrum_data[g_yes_power_spectrum_data_size] = {
     8, 89, 8, 0, 0, 0, 0, 0, 0, 0, 0, 4, 13, 1, 6, 23, 20, 6, 4, 0, 0, 0,

tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/yes_power_spectrum_data.h

@@ -18,12 +18,12 @@ limitations under the License.
 // This is the expected result of running the sample data in
 // yes_30ms_sample_data.cc through through the preprocessing pipeline.
 
-#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_YES_POWER_SPECTRUM_DATA_H_
+#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_SIMPLE_FEATURES_YES_POWER_SPECTRUM_DATA_H_
-#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_YES_POWER_SPECTRUM_DATA_H_
+#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_SIMPLE_FEATURES_YES_POWER_SPECTRUM_DATA_H_
 
 #include <cstdint>
 
 constexpr int g_yes_power_spectrum_data_size = 43;
 extern const uint8_t g_yes_power_spectrum_data[];
 
-#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_YES_POWER_SPECTRUM_DATA_H_
+#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_SIMPLE_FEATURES_YES_POWER_SPECTRUM_DATA_H_

tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/yes_simple_features_data.cc

@@ -13,7 +13,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 ==============================================================================*/
 
-#include "tensorflow/lite/experimental/micro/examples/micro_speech/yes_features_data.h"
+#include "tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/yes_simple_features_data.h"
 
 /* File automatically created by
  * tensorflow/examples/speech_commands/wav_to_features.py \
@@ -22,15 +22,15 @@ limitations under the License.
  * --window_size_ms=30 \
  * --window_stride_ms=20 \
  * --feature_bin_count=40 \
- * --quantize \
+ * --quantize=1 \
  * --preprocess="average" \
  * --input_wav="speech_commands_test_set_v0.02/yes/f2e59fea_nohash_1.wav" \
- * --output_c_file="yes_features_data.cc" \
+ * --output_c_file="yes_simple_features_data.cc" \
  */
 
-const int g_yes_f2e59fea_nohash_1_width = 43;
+const int g_yes_simple_f2e59fea_nohash_1_width = 43;
-const int g_yes_f2e59fea_nohash_1_height = 49;
+const int g_yes_simple_f2e59fea_nohash_1_height = 49;
-const unsigned char g_yes_f2e59fea_nohash_1_data[] = {
+const unsigned char g_yes_simple_f2e59fea_nohash_1_data[] = {
     0,  0,  0,   0,   0,   0,  0,   0,   0,  0,  0,   0,   0,  0,  0,   0,  0,
     0,  0,  0,   0,   0,   0,  0,   0,   0,  0,  0,   0,   0,  0,  0,   0,  0,
     0,  0,  0,   0,   0,   0,  0,   0,   0,  0,  0,   0,   0,  0,  0,   0,  0,

tensorflow/lite/experimental/micro/examples/micro_speech/simple_features/yes_simple_features_data.h

@@ -13,11 +13,11 @@ See the License for the specific language governing permissions and
 limitations under the License.
 ==============================================================================*/
 
-#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_YES_FEATURES_DATA_H_
+#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_SIMPLE_FEATURES_YES_SIMPLE_FEATURES_DATA_H_
-#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_YES_FEATURES_DATA_H_
+#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_SIMPLE_FEATURES_YES_SIMPLE_FEATURES_DATA_H_
 
-extern const int g_yes_f2e59fea_nohash_1_width;
+extern const int g_yes_simple_f2e59fea_nohash_1_width;
-extern const int g_yes_f2e59fea_nohash_1_height;
+extern const int g_yes_simple_f2e59fea_nohash_1_height;
-extern const unsigned char g_yes_f2e59fea_nohash_1_data[];
+extern const unsigned char g_yes_simple_f2e59fea_nohash_1_data[];
 
-#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_YES_FEATURES_DATA_H_
+#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_SIMPLE_FEATURES_YES_SIMPLE_FEATURES_DATA_H_

tensorflow/lite/experimental/micro/examples/micro_speech/yes_1000ms_sample_data.h

@@ -0,0 +1,29 @@
+/* Copyright 2019 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+
+// This data was created from the PCM data in a WAV file held in v2 of the
+// Speech Commands test dataset, at the path:
+// speech_commands_test_set_v0.02/yes/f2e59fea_nohash_1.wav
+// This should contain all 16,000 samples from the one-second file.
+
+#ifndef TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_YES_1000MS_SAMPLE_DATA_H_
+#define TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_YES_1000MS_SAMPLE_DATA_H_
+
+#include <cstdint>
+
+extern const int g_yes_1000ms_sample_data_size;
+extern const int16_t g_yes_1000ms_sample_data[];
+
+#endif  // TENSORFLOW_LITE_EXPERIMENTAL_MICRO_EXAMPLES_MICRO_SPEECH_YES_1000MS_SAMPLE_DATA_H_

tensorflow/lite/experimental/micro/testing/micro_test.h

@@ -110,8 +110,8 @@ extern tflite::ErrorReporter* reporter;
 #define TF_LITE_MICRO_EXPECT_EQ(x, y)                                          \
   do {                                                                         \
     if ((x) != (y)) {                                                          \
-      micro_test::reporter->Report(#x " == " #y " failed at %s:%d", __FILE__, \
+      micro_test::reporter->Report(#x " == " #y " failed at %s:%d (%d vs %d)", \
-                                   __LINE__);                                 \
+                                   __FILE__, __LINE__, (x), (y));              \
       micro_test::did_test_fail = true;                                        \
     }                                                                          \
   } while (false)

tensorflow/lite/experimental/micro/tools/make/download_dependencies.sh

@@ -39,6 +39,7 @@ AM_SDK_URL="http://s3.asia.ambiqmicro.com/downloads/AmbiqSuite-Rel2.0.0.zip"
 AP3_URL="https://github.com/AmbiqMicro/TFLiteMicro_Apollo3/archive/dfbcef9a57276c087d95aab7cb234f1d4c9eaaba.zip"
 CUST_CMSIS_URL="https://github.com/AmbiqMicro/TFLiteMicro_CustCMSIS/archive/8f63966c5692e6a3a83956efd2e4aed77c4c9949.zip"
 GCC_EMBEDDED_URL="https://developer.arm.com/-/media/Files/downloads/gnu-rm/7-2018q2/gcc-arm-none-eabi-7-2018-q2-update-linux.tar.bz2"
+KISSFFT_URL="http://downloads.sourceforge.net/project/kissfft/kissfft/v1_3_0/kiss_fft130.zip"
 
 download_and_extract() {
   local usage="Usage: download_and_extract URL DIR"
@@ -100,6 +101,15 @@ patch_am_sdk() {
   echo "Finished preparing Apollo3 files"
 }
 
+patch_kissfft() {
+  sed -i -E "s@#ifdef FIXED_POINT@// Patched automatically by download_dependencies.sh so default is 16 bit.\n#ifndef FIXED_POINT\n#define FIXED_POINT (16)\n#endif\n// End patch.\n\n#ifdef FIXED_POINT@g" tensorflow/lite/experimental/micro/tools/make/downloads/kissfft/kiss_fft.h
+  sed -i -E "s@#define KISS_FFT_MALLOC malloc@#define KISS_FFT_MALLOC(X) (void*)(0) /* Patched. */@g" tensorflow/lite/experimental/micro/tools/make/downloads/kissfft/kiss_fft.h
+  sed -i -E "s@#define KISS_FFT_FREE free@#define KISS_FFT_FREE(X) /* Patched. */@g" tensorflow/lite/experimental/micro/tools/make/downloads/kissfft/kiss_fft.h
+  sed -i -E "s@(fprintf.*\);)@/* \1 */@g" tensorflow/lite/experimental/micro/tools/make/downloads/kissfft/tools/kiss_fftr.c
+  sed -i -E "s@(exit.*\);)@return; /* \1 */@g" tensorflow/lite/experimental/micro/tools/make/downloads/kissfft/tools/kiss_fftr.c
+  echo "Finished patching kissfft"
+}
+
 download_and_extract "${GEMMLOWP_URL}" "${DOWNLOADS_DIR}/gemmlowp"
 download_and_extract "${FLATBUFFERS_URL}" "${DOWNLOADS_DIR}/flatbuffers"
 download_and_extract "${CMSIS_URL}" "${DOWNLOADS_DIR}/cmsis"
@@ -111,5 +121,7 @@ patch_am_sdk "${DOWNLOADS_DIR}/AmbiqSuite-Rel2.0.0"
 download_and_extract "${AP3_URL}" "${DOWNLOADS_DIR}/apollo3_ext"
 download_and_extract "${CUST_CMSIS_URL}" "${DOWNLOADS_DIR}/CMSIS_ext"
 download_and_extract "${GCC_EMBEDDED_URL}" "${DOWNLOADS_DIR}/gcc_embedded"
+download_and_extract "${KISSFFT_URL}" "${DOWNLOADS_DIR}/kissfft"
+patch_kissfft "${DOWNLOADS_DIR}/kissfft"
 
 echo "download_dependencies.sh completed successfully." >&2