modules/audio_processing/vad/vad_audio_proc.cc - src - Git at Google

 /*
  *  Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */

 #include "modules/audio_processing/vad/vad_audio_proc.h"

 #include <math.h>
 #include <stdio.h>
 #include <string.h>

 #include "common_audio/third_party/fft4g/fft4g.h"
 #include "modules/audio_processing/vad/pitch_internal.h"
 #include "modules/audio_processing/vad/pole_zero_filter.h"
 #include "modules/audio_processing/vad/vad_audio_proc_internal.h"
 #include "rtc_base/checks.h"
 extern "C" {
 #include "modules/audio_coding/codecs/isac/main/source/filter_functions.h"
 #include "modules/audio_coding/codecs/isac/main/source/isac_vad.h"
 #include "modules/audio_coding/codecs/isac/main/source/pitch_estimator.h"
 #include "modules/audio_coding/codecs/isac/main/source/structs.h"
 }

 namespace webrtc {

 // The following structures are declared anonymous in iSAC's structs.h. To
 // forward declare them, we use this derived class trick.
 struct VadAudioProc::PitchAnalysisStruct : public ::PitchAnalysisStruct {};
 struct VadAudioProc::PreFiltBankstr : public ::PreFiltBankstr {};

 static constexpr float kFrequencyResolution =
     kSampleRateHz / static_cast<float>(VadAudioProc::kDftSize);
 static constexpr int kSilenceRms = 5;

 // TODO(turajs): Make a Create or Init for VadAudioProc.
 VadAudioProc::VadAudioProc()
     : audio_buffer_(),
       num_buffer_samples_(kNumPastSignalSamples),
       log_old_gain_(-2),
       old_lag_(50),  // Arbitrary but valid as pitch-lag (in samples).
       pitch_analysis_handle_(new PitchAnalysisStruct),
       pre_filter_handle_(new PreFiltBankstr),
       high_pass_filter_(PoleZeroFilter::Create(kCoeffNumerator,
                                                kFilterOrder,
                                                kCoeffDenominator,
                                                kFilterOrder)) {
   static_assert(kNumPastSignalSamples + kNumSubframeSamples ==
                     sizeof(kLpcAnalWin) / sizeof(kLpcAnalWin[0]),
                 "lpc analysis window incorrect size");
   static_assert(kLpcOrder + 1 == sizeof(kCorrWeight) / sizeof(kCorrWeight[0]),
                 "correlation weight incorrect size");

   // TODO(turajs): Are we doing too much in the constructor?
   float data[kDftSize];
   // Make FFT to initialize.
   ip_[0] = 0;
   WebRtc_rdft(kDftSize, 1, data, ip_, w_fft_);
   // TODO(turajs): Need to initialize high-pass filter.

   // Initialize iSAC components.
   WebRtcIsac_InitPreFilterbank(pre_filter_handle_.get());
   WebRtcIsac_InitPitchAnalysis(pitch_analysis_handle_.get());
 }

 VadAudioProc::~VadAudioProc() {}

 void VadAudioProc::ResetBuffer() {
   memcpy(audio_buffer_, &audio_buffer_[kNumSamplesToProcess],
          sizeof(audio_buffer_[0]) * kNumPastSignalSamples);
   num_buffer_samples_ = kNumPastSignalSamples;
 }

 int VadAudioProc::ExtractFeatures(const int16_t* frame,
                                   size_t length,
                                   AudioFeatures* features) {
   features->num_frames = 0;
   if (length != kNumSubframeSamples) {
     return -1;
   }

   // High-pass filter to remove the DC component and very low frequency content.
   // We have experienced that this high-pass filtering improves voice/non-voiced
   // classification.
   if (high_pass_filter_->Filter(frame, kNumSubframeSamples,
                                 &audio_buffer_[num_buffer_samples_]) != 0) {
     return -1;
   }

   num_buffer_samples_ += kNumSubframeSamples;
   if (num_buffer_samples_ < kBufferLength) {
     return 0;
   }
   RTC_DCHECK_EQ(num_buffer_samples_, kBufferLength);
   features->num_frames = kNum10msSubframes;
   features->silence = false;

   Rms(features->rms, kMaxNumFrames);
   for (size_t i = 0; i < kNum10msSubframes; ++i) {
     if (features->rms[i] < kSilenceRms) {
       // PitchAnalysis can cause NaNs in the pitch gain if it's fed silence.
       // Bail out here instead.
       features->silence = true;
       ResetBuffer();
       return 0;
     }
   }

   PitchAnalysis(features->log_pitch_gain, features->pitch_lag_hz,
                 kMaxNumFrames);
   FindFirstSpectralPeaks(features->spectral_peak, kMaxNumFrames);
   ResetBuffer();
   return 0;
 }

 // Computes |kLpcOrder + 1| correlation coefficients.
 void VadAudioProc::SubframeCorrelation(double* corr,
                                        size_t length_corr,
                                        size_t subframe_index) {
   RTC_DCHECK_GE(length_corr, kLpcOrder + 1);
   double windowed_audio[kNumSubframeSamples + kNumPastSignalSamples];
   size_t buffer_index = subframe_index * kNumSubframeSamples;

   for (size_t n = 0; n < kNumSubframeSamples + kNumPastSignalSamples; n++)
     windowed_audio[n] = audio_buffer_[buffer_index++] * kLpcAnalWin[n];

   WebRtcIsac_AutoCorr(corr, windowed_audio,
                       kNumSubframeSamples + kNumPastSignalSamples, kLpcOrder);
 }

 // Compute |kNum10msSubframes| sets of LPC coefficients, one per 10 ms input.
 // The analysis window is 15 ms long and it is centered on the first half of
 // each 10ms sub-frame. This is equivalent to computing LPC coefficients for the
 // first half of each 10 ms subframe.
 void VadAudioProc::GetLpcPolynomials(double* lpc, size_t length_lpc) {
   RTC_DCHECK_GE(length_lpc, kNum10msSubframes * (kLpcOrder + 1));
   double corr[kLpcOrder + 1];
   double reflec_coeff[kLpcOrder];
   for (size_t i = 0, offset_lpc = 0; i < kNum10msSubframes;
        i++, offset_lpc += kLpcOrder + 1) {
     SubframeCorrelation(corr, kLpcOrder + 1, i);
     corr[0] *= 1.0001;
     // This makes Lev-Durb a bit more stable.
     for (size_t k = 0; k < kLpcOrder + 1; k++) {
       corr[k] *= kCorrWeight[k];
     }
     WebRtcIsac_LevDurb(&lpc[offset_lpc], reflec_coeff, corr, kLpcOrder);
   }
 }

 // Fit a second order curve to these 3 points and find the location of the
 // extremum. The points are inverted before curve fitting.
 static float QuadraticInterpolation(float prev_val,
                                     float curr_val,
                                     float next_val) {
   // Doing the interpolation in |1 / A(z)|^2.
   float fractional_index = 0;
   next_val = 1.0f / next_val;
   prev_val = 1.0f / prev_val;
   curr_val = 1.0f / curr_val;

   fractional_index =
       -(next_val - prev_val) * 0.5f / (next_val + prev_val - 2.f * curr_val);
   RTC_DCHECK_LT(fabs(fractional_index), 1);
   return fractional_index;
 }

 // 1 / A(z), where A(z) is defined by |lpc| is a model of the spectral envelope
 // of the input signal. The local maximum of the spectral envelope corresponds
 // with the local minimum of A(z). It saves complexity, as we save one
 // inversion. Furthermore, we find the first local maximum of magnitude squared,
 // to save on one square root.
 void VadAudioProc::FindFirstSpectralPeaks(double* f_peak,
                                           size_t length_f_peak) {
   RTC_DCHECK_GE(length_f_peak, kNum10msSubframes);
   double lpc[kNum10msSubframes * (kLpcOrder + 1)];
   // For all sub-frames.
   GetLpcPolynomials(lpc, kNum10msSubframes * (kLpcOrder + 1));

   const size_t kNumDftCoefficients = kDftSize / 2 + 1;
   float data[kDftSize];

   for (size_t i = 0; i < kNum10msSubframes; i++) {
     // Convert to float with zero pad.
     memset(data, 0, sizeof(data));
     for (size_t n = 0; n < kLpcOrder + 1; n++) {
       data[n] = static_cast<float>(lpc[i * (kLpcOrder + 1) + n]);
     }
     // Transform to frequency domain.
     WebRtc_rdft(kDftSize, 1, data, ip_, w_fft_);

     size_t index_peak = 0;
     float prev_magn_sqr = data[0] * data[0];
     float curr_magn_sqr = data[2] * data[2] + data[3] * data[3];
     float next_magn_sqr;
     bool found_peak = false;
     for (size_t n = 2; n < kNumDftCoefficients - 1; n++) {
       next_magn_sqr =
           data[2 * n] * data[2 * n] + data[2 * n + 1] * data[2 * n + 1];
       if (curr_magn_sqr < prev_magn_sqr && curr_magn_sqr < next_magn_sqr) {
         found_peak = true;
         index_peak = n - 1;
         break;
       }
       prev_magn_sqr = curr_magn_sqr;
       curr_magn_sqr = next_magn_sqr;
     }
     float fractional_index = 0;
     if (!found_peak) {
       // Checking if |kNumDftCoefficients - 1| is the local minimum.
       next_magn_sqr = data[1] * data[1];
       if (curr_magn_sqr < prev_magn_sqr && curr_magn_sqr < next_magn_sqr) {
         index_peak = kNumDftCoefficients - 1;
       }
     } else {
       // A peak is found, do a simple quadratic interpolation to get a more
       // accurate estimate of the peak location.
       fractional_index =
           QuadraticInterpolation(prev_magn_sqr, curr_magn_sqr, next_magn_sqr);
     }
     f_peak[i] = (index_peak + fractional_index) * kFrequencyResolution;
   }
 }

 // Using iSAC functions to estimate pitch gains & lags.
 void VadAudioProc::PitchAnalysis(double* log_pitch_gains,
                                  double* pitch_lags_hz,
                                  size_t length) {
   // TODO(turajs): This can be "imported" from iSAC & and the next two
   // constants.
   RTC_DCHECK_GE(length, kNum10msSubframes);
   const int kNumPitchSubframes = 4;
   double gains[kNumPitchSubframes];
   double lags[kNumPitchSubframes];

   const int kNumSubbandFrameSamples = 240;
   const int kNumLookaheadSamples = 24;

   float lower[kNumSubbandFrameSamples];
   float upper[kNumSubbandFrameSamples];
   double lower_lookahead[kNumSubbandFrameSamples];
   double upper_lookahead[kNumSubbandFrameSamples];
   double lower_lookahead_pre_filter[kNumSubbandFrameSamples +
                                     kNumLookaheadSamples];

   // Split signal to lower and upper bands
   WebRtcIsac_SplitAndFilterFloat(&audio_buffer_[kNumPastSignalSamples], lower,
                                  upper, lower_lookahead, upper_lookahead,
                                  pre_filter_handle_.get());
   WebRtcIsac_PitchAnalysis(lower_lookahead, lower_lookahead_pre_filter,
                            pitch_analysis_handle_.get(), lags, gains);

   // Lags are computed on lower-band signal with sampling rate half of the
   // input signal.
   GetSubframesPitchParameters(
       kSampleRateHz / 2, gains, lags, kNumPitchSubframes, kNum10msSubframes,
       &log_old_gain_, &old_lag_, log_pitch_gains, pitch_lags_hz);
 }

 void VadAudioProc::Rms(double* rms, size_t length_rms) {
   RTC_DCHECK_GE(length_rms, kNum10msSubframes);
   size_t offset = kNumPastSignalSamples;
   for (size_t i = 0; i < kNum10msSubframes; i++) {
     rms[i] = 0;
     for (size_t n = 0; n < kNumSubframeSamples; n++, offset++)
       rms[i] += audio_buffer_[offset] * audio_buffer_[offset];
     rms[i] = sqrt(rms[i] / kNumSubframeSamples);
   }
 }

 }  // namespace webrtc
	/*
	* Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
	*
	* Use of this source code is governed by a BSD-style license
	* that can be found in the LICENSE file in the root of the source
	* tree. An additional intellectual property rights grant can be found
	* in the file PATENTS. All contributing project authors may
	* be found in the AUTHORS file in the root of the source tree.
	*/

	#include "modules/audio_processing/vad/vad_audio_proc.h"

	#include <math.h>
	#include <stdio.h>
	#include <string.h>

	#include "common_audio/third_party/fft4g/fft4g.h"
	#include "modules/audio_processing/vad/pitch_internal.h"
	#include "modules/audio_processing/vad/pole_zero_filter.h"
	#include "modules/audio_processing/vad/vad_audio_proc_internal.h"
	#include "rtc_base/checks.h"
	extern "C" {
	#include "modules/audio_coding/codecs/isac/main/source/filter_functions.h"
	#include "modules/audio_coding/codecs/isac/main/source/isac_vad.h"
	#include "modules/audio_coding/codecs/isac/main/source/pitch_estimator.h"
	#include "modules/audio_coding/codecs/isac/main/source/structs.h"
	}

	namespace webrtc {

	// The following structures are declared anonymous in iSAC's structs.h. To
	// forward declare them, we use this derived class trick.
	struct VadAudioProc::PitchAnalysisStruct : public ::PitchAnalysisStruct {};
	struct VadAudioProc::PreFiltBankstr : public ::PreFiltBankstr {};

	static constexpr float kFrequencyResolution =
	kSampleRateHz / static_cast<float>(VadAudioProc::kDftSize);
	static constexpr int kSilenceRms = 5;

	// TODO(turajs): Make a Create or Init for VadAudioProc.
	VadAudioProc::VadAudioProc()
	: audio_buffer_(),
	num_buffer_samples_(kNumPastSignalSamples),
	log_old_gain_(-2),
	old_lag_(50), // Arbitrary but valid as pitch-lag (in samples).
	pitch_analysis_handle_(new PitchAnalysisStruct),
	pre_filter_handle_(new PreFiltBankstr),
	high_pass_filter_(PoleZeroFilter::Create(kCoeffNumerator,
	kFilterOrder,
	kCoeffDenominator,
	kFilterOrder)) {
	static_assert(kNumPastSignalSamples + kNumSubframeSamples ==
	sizeof(kLpcAnalWin) / sizeof(kLpcAnalWin[0]),
	"lpc analysis window incorrect size");
	static_assert(kLpcOrder + 1 == sizeof(kCorrWeight) / sizeof(kCorrWeight[0]),
	"correlation weight incorrect size");

	// TODO(turajs): Are we doing too much in the constructor?
	float data[kDftSize];
	// Make FFT to initialize.
	ip_[0] = 0;
	WebRtc_rdft(kDftSize, 1, data, ip_, w_fft_);
	// TODO(turajs): Need to initialize high-pass filter.

	// Initialize iSAC components.
	WebRtcIsac_InitPreFilterbank(pre_filter_handle_.get());
	WebRtcIsac_InitPitchAnalysis(pitch_analysis_handle_.get());
	}

	VadAudioProc::~VadAudioProc() {}

	void VadAudioProc::ResetBuffer() {
	memcpy(audio_buffer_, &audio_buffer_[kNumSamplesToProcess],
	sizeof(audio_buffer_[0]) * kNumPastSignalSamples);
	num_buffer_samples_ = kNumPastSignalSamples;
	}

	int VadAudioProc::ExtractFeatures(const int16_t* frame,
	size_t length,
	AudioFeatures* features) {
	features->num_frames = 0;
	if (length != kNumSubframeSamples) {
	return -1;
	}

	// High-pass filter to remove the DC component and very low frequency content.
	// We have experienced that this high-pass filtering improves voice/non-voiced
	// classification.
	if (high_pass_filter_->Filter(frame, kNumSubframeSamples,
	&audio_buffer_[num_buffer_samples_]) != 0) {
	return -1;
	}

	num_buffer_samples_ += kNumSubframeSamples;
	if (num_buffer_samples_ < kBufferLength) {
	return 0;
	}
	RTC_DCHECK_EQ(num_buffer_samples_, kBufferLength);
	features->num_frames = kNum10msSubframes;
	features->silence = false;

	Rms(features->rms, kMaxNumFrames);
	for (size_t i = 0; i < kNum10msSubframes; ++i) {
	if (features->rms[i] < kSilenceRms) {
	// PitchAnalysis can cause NaNs in the pitch gain if it's fed silence.
	// Bail out here instead.
	features->silence = true;
	ResetBuffer();
	return 0;
	}
	}

	PitchAnalysis(features->log_pitch_gain, features->pitch_lag_hz,
	kMaxNumFrames);
	FindFirstSpectralPeaks(features->spectral_peak, kMaxNumFrames);
	ResetBuffer();
	return 0;
	}

	// Computes \|kLpcOrder + 1\| correlation coefficients.
	void VadAudioProc::SubframeCorrelation(double* corr,
	size_t length_corr,
	size_t subframe_index) {
	RTC_DCHECK_GE(length_corr, kLpcOrder + 1);
	double windowed_audio[kNumSubframeSamples + kNumPastSignalSamples];
	size_t buffer_index = subframe_index * kNumSubframeSamples;

	for (size_t n = 0; n < kNumSubframeSamples + kNumPastSignalSamples; n++)
	windowed_audio[n] = audio_buffer_[buffer_index++] * kLpcAnalWin[n];

	WebRtcIsac_AutoCorr(corr, windowed_audio,
	kNumSubframeSamples + kNumPastSignalSamples, kLpcOrder);
	}

	// Compute \|kNum10msSubframes\| sets of LPC coefficients, one per 10 ms input.
	// The analysis window is 15 ms long and it is centered on the first half of
	// each 10ms sub-frame. This is equivalent to computing LPC coefficients for the
	// first half of each 10 ms subframe.
	void VadAudioProc::GetLpcPolynomials(double* lpc, size_t length_lpc) {
	RTC_DCHECK_GE(length_lpc, kNum10msSubframes * (kLpcOrder + 1));
	double corr[kLpcOrder + 1];
	double reflec_coeff[kLpcOrder];
	for (size_t i = 0, offset_lpc = 0; i < kNum10msSubframes;
	i++, offset_lpc += kLpcOrder + 1) {
	SubframeCorrelation(corr, kLpcOrder + 1, i);
	corr[0] *= 1.0001;
	// This makes Lev-Durb a bit more stable.
	for (size_t k = 0; k < kLpcOrder + 1; k++) {
	corr[k] *= kCorrWeight[k];
	}
	WebRtcIsac_LevDurb(&lpc[offset_lpc], reflec_coeff, corr, kLpcOrder);
	}
	}

	// Fit a second order curve to these 3 points and find the location of the
	// extremum. The points are inverted before curve fitting.
	static float QuadraticInterpolation(float prev_val,
	float curr_val,
	float next_val) {
	// Doing the interpolation in \|1 / A(z)\|^2.
	float fractional_index = 0;
	next_val = 1.0f / next_val;
	prev_val = 1.0f / prev_val;
	curr_val = 1.0f / curr_val;

	fractional_index =
	-(next_val - prev_val) * 0.5f / (next_val + prev_val - 2.f * curr_val);
	RTC_DCHECK_LT(fabs(fractional_index), 1);
	return fractional_index;
	}

	// 1 / A(z), where A(z) is defined by \|lpc\| is a model of the spectral envelope
	// of the input signal. The local maximum of the spectral envelope corresponds
	// with the local minimum of A(z). It saves complexity, as we save one
	// inversion. Furthermore, we find the first local maximum of magnitude squared,
	// to save on one square root.
	void VadAudioProc::FindFirstSpectralPeaks(double* f_peak,
	size_t length_f_peak) {
	RTC_DCHECK_GE(length_f_peak, kNum10msSubframes);
	double lpc[kNum10msSubframes * (kLpcOrder + 1)];
	// For all sub-frames.
	GetLpcPolynomials(lpc, kNum10msSubframes * (kLpcOrder + 1));

	const size_t kNumDftCoefficients = kDftSize / 2 + 1;
	float data[kDftSize];

	for (size_t i = 0; i < kNum10msSubframes; i++) {
	// Convert to float with zero pad.
	memset(data, 0, sizeof(data));
	for (size_t n = 0; n < kLpcOrder + 1; n++) {
	data[n] = static_cast<float>(lpc[i * (kLpcOrder + 1) + n]);
	}
	// Transform to frequency domain.
	WebRtc_rdft(kDftSize, 1, data, ip_, w_fft_);

	size_t index_peak = 0;
	float prev_magn_sqr = data[0] * data[0];
	float curr_magn_sqr = data[2] * data[2] + data[3] * data[3];
	float next_magn_sqr;
	bool found_peak = false;
	for (size_t n = 2; n < kNumDftCoefficients - 1; n++) {
	next_magn_sqr =
	data[2 * n] * data[2 * n] + data[2 * n + 1] * data[2 * n + 1];
	if (curr_magn_sqr < prev_magn_sqr && curr_magn_sqr < next_magn_sqr) {
	found_peak = true;
	index_peak = n - 1;
	break;
	}
	prev_magn_sqr = curr_magn_sqr;
	curr_magn_sqr = next_magn_sqr;
	}
	float fractional_index = 0;
	if (!found_peak) {
	// Checking if \|kNumDftCoefficients - 1\| is the local minimum.
	next_magn_sqr = data[1] * data[1];
	if (curr_magn_sqr < prev_magn_sqr && curr_magn_sqr < next_magn_sqr) {
	index_peak = kNumDftCoefficients - 1;
	}
	} else {
	// A peak is found, do a simple quadratic interpolation to get a more
	// accurate estimate of the peak location.
	fractional_index =
	QuadraticInterpolation(prev_magn_sqr, curr_magn_sqr, next_magn_sqr);
	}
	f_peak[i] = (index_peak + fractional_index) * kFrequencyResolution;
	}
	}

	// Using iSAC functions to estimate pitch gains & lags.
	void VadAudioProc::PitchAnalysis(double* log_pitch_gains,
	double* pitch_lags_hz,
	size_t length) {
	// TODO(turajs): This can be "imported" from iSAC & and the next two
	// constants.
	RTC_DCHECK_GE(length, kNum10msSubframes);
	const int kNumPitchSubframes = 4;
	double gains[kNumPitchSubframes];
	double lags[kNumPitchSubframes];

	const int kNumSubbandFrameSamples = 240;
	const int kNumLookaheadSamples = 24;

	float lower[kNumSubbandFrameSamples];
	float upper[kNumSubbandFrameSamples];
	double lower_lookahead[kNumSubbandFrameSamples];
	double upper_lookahead[kNumSubbandFrameSamples];
	double lower_lookahead_pre_filter[kNumSubbandFrameSamples +
	kNumLookaheadSamples];

	// Split signal to lower and upper bands
	WebRtcIsac_SplitAndFilterFloat(&audio_buffer_[kNumPastSignalSamples], lower,
	upper, lower_lookahead, upper_lookahead,
	pre_filter_handle_.get());
	WebRtcIsac_PitchAnalysis(lower_lookahead, lower_lookahead_pre_filter,
	pitch_analysis_handle_.get(), lags, gains);

	// Lags are computed on lower-band signal with sampling rate half of the
	// input signal.
	GetSubframesPitchParameters(
	kSampleRateHz / 2, gains, lags, kNumPitchSubframes, kNum10msSubframes,
	&log_old_gain_, &old_lag_, log_pitch_gains, pitch_lags_hz);
	}

	void VadAudioProc::Rms(double* rms, size_t length_rms) {
	RTC_DCHECK_GE(length_rms, kNum10msSubframes);
	size_t offset = kNumPastSignalSamples;
	for (size_t i = 0; i < kNum10msSubframes; i++) {
	rms[i] = 0;
	for (size_t n = 0; n < kNumSubframeSamples; n++, offset++)
	rms[i] += audio_buffer_[offset] * audio_buffer_[offset];
	rms[i] = sqrt(rms[i] / kNumSubframeSamples);
	}
	}

	} // namespace webrtc