276 lines
11 KiB
C++
276 lines
11 KiB
C++
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/*
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* Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#include "modules/audio_processing/vad/vad_audio_proc.h"
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#include <math.h>
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#include <stdio.h>
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#include <string.h>
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#include "common_audio/third_party/ooura/fft_size_256/fft4g.h"
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#include "modules/audio_processing/vad/pitch_internal.h"
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#include "modules/audio_processing/vad/pole_zero_filter.h"
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#include "modules/audio_processing/vad/vad_audio_proc_internal.h"
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#include "rtc_base/checks.h"
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extern "C" {
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#include "modules/audio_coding/codecs/isac/main/source/filter_functions.h"
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#include "modules/audio_coding/codecs/isac/main/source/isac_vad.h"
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#include "modules/audio_coding/codecs/isac/main/source/pitch_estimator.h"
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#include "modules/audio_coding/codecs/isac/main/source/structs.h"
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}
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namespace webrtc {
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// The following structures are declared anonymous in iSAC's structs.h. To
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// forward declare them, we use this derived class trick.
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struct VadAudioProc::PitchAnalysisStruct : public ::PitchAnalysisStruct {};
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struct VadAudioProc::PreFiltBankstr : public ::PreFiltBankstr {};
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static constexpr float kFrequencyResolution =
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kSampleRateHz / static_cast<float>(VadAudioProc::kDftSize);
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static constexpr int kSilenceRms = 5;
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// TODO(turajs): Make a Create or Init for VadAudioProc.
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VadAudioProc::VadAudioProc()
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: audio_buffer_(),
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num_buffer_samples_(kNumPastSignalSamples),
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log_old_gain_(-2),
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old_lag_(50), // Arbitrary but valid as pitch-lag (in samples).
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pitch_analysis_handle_(new PitchAnalysisStruct),
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pre_filter_handle_(new PreFiltBankstr),
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high_pass_filter_(PoleZeroFilter::Create(kCoeffNumerator,
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kFilterOrder,
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kCoeffDenominator,
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kFilterOrder)) {
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static_assert(kNumPastSignalSamples + kNumSubframeSamples ==
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sizeof(kLpcAnalWin) / sizeof(kLpcAnalWin[0]),
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"lpc analysis window incorrect size");
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static_assert(kLpcOrder + 1 == sizeof(kCorrWeight) / sizeof(kCorrWeight[0]),
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"correlation weight incorrect size");
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// TODO(turajs): Are we doing too much in the constructor?
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float data[kDftSize];
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// Make FFT to initialize.
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ip_[0] = 0;
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WebRtc_rdft(kDftSize, 1, data, ip_, w_fft_);
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// TODO(turajs): Need to initialize high-pass filter.
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// Initialize iSAC components.
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WebRtcIsac_InitPreFilterbank(pre_filter_handle_.get());
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WebRtcIsac_InitPitchAnalysis(pitch_analysis_handle_.get());
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}
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VadAudioProc::~VadAudioProc() {}
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void VadAudioProc::ResetBuffer() {
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memcpy(audio_buffer_, &audio_buffer_[kNumSamplesToProcess],
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sizeof(audio_buffer_[0]) * kNumPastSignalSamples);
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num_buffer_samples_ = kNumPastSignalSamples;
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}
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int VadAudioProc::ExtractFeatures(const int16_t* frame,
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size_t length,
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AudioFeatures* features) {
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features->num_frames = 0;
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if (length != kNumSubframeSamples) {
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return -1;
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}
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// High-pass filter to remove the DC component and very low frequency content.
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// We have experienced that this high-pass filtering improves voice/non-voiced
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// classification.
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if (high_pass_filter_->Filter(frame, kNumSubframeSamples,
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&audio_buffer_[num_buffer_samples_]) != 0) {
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return -1;
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}
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num_buffer_samples_ += kNumSubframeSamples;
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if (num_buffer_samples_ < kBufferLength) {
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return 0;
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}
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RTC_DCHECK_EQ(num_buffer_samples_, kBufferLength);
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features->num_frames = kNum10msSubframes;
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features->silence = false;
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Rms(features->rms, kMaxNumFrames);
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for (size_t i = 0; i < kNum10msSubframes; ++i) {
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if (features->rms[i] < kSilenceRms) {
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// PitchAnalysis can cause NaNs in the pitch gain if it's fed silence.
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// Bail out here instead.
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features->silence = true;
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ResetBuffer();
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return 0;
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}
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}
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PitchAnalysis(features->log_pitch_gain, features->pitch_lag_hz,
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kMaxNumFrames);
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FindFirstSpectralPeaks(features->spectral_peak, kMaxNumFrames);
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ResetBuffer();
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return 0;
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}
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// Computes |kLpcOrder + 1| correlation coefficients.
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void VadAudioProc::SubframeCorrelation(double* corr,
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size_t length_corr,
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size_t subframe_index) {
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RTC_DCHECK_GE(length_corr, kLpcOrder + 1);
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double windowed_audio[kNumSubframeSamples + kNumPastSignalSamples];
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size_t buffer_index = subframe_index * kNumSubframeSamples;
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for (size_t n = 0; n < kNumSubframeSamples + kNumPastSignalSamples; n++)
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windowed_audio[n] = audio_buffer_[buffer_index++] * kLpcAnalWin[n];
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WebRtcIsac_AutoCorr(corr, windowed_audio,
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kNumSubframeSamples + kNumPastSignalSamples, kLpcOrder);
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}
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// Compute `kNum10msSubframes` sets of LPC coefficients, one per 10 ms input.
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// The analysis window is 15 ms long and it is centered on the first half of
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// each 10ms sub-frame. This is equivalent to computing LPC coefficients for the
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// first half of each 10 ms subframe.
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void VadAudioProc::GetLpcPolynomials(double* lpc, size_t length_lpc) {
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RTC_DCHECK_GE(length_lpc, kNum10msSubframes * (kLpcOrder + 1));
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double corr[kLpcOrder + 1];
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double reflec_coeff[kLpcOrder];
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for (size_t i = 0, offset_lpc = 0; i < kNum10msSubframes;
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i++, offset_lpc += kLpcOrder + 1) {
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SubframeCorrelation(corr, kLpcOrder + 1, i);
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corr[0] *= 1.0001;
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// This makes Lev-Durb a bit more stable.
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for (size_t k = 0; k < kLpcOrder + 1; k++) {
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corr[k] *= kCorrWeight[k];
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}
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WebRtcIsac_LevDurb(&lpc[offset_lpc], reflec_coeff, corr, kLpcOrder);
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}
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}
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// Fit a second order curve to these 3 points and find the location of the
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// extremum. The points are inverted before curve fitting.
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static float QuadraticInterpolation(float prev_val,
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float curr_val,
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float next_val) {
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// Doing the interpolation in |1 / A(z)|^2.
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float fractional_index = 0;
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next_val = 1.0f / next_val;
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prev_val = 1.0f / prev_val;
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curr_val = 1.0f / curr_val;
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fractional_index =
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-(next_val - prev_val) * 0.5f / (next_val + prev_val - 2.f * curr_val);
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RTC_DCHECK_LT(fabs(fractional_index), 1);
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return fractional_index;
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}
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// 1 / A(z), where A(z) is defined by `lpc` is a model of the spectral envelope
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// of the input signal. The local maximum of the spectral envelope corresponds
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// with the local minimum of A(z). It saves complexity, as we save one
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// inversion. Furthermore, we find the first local maximum of magnitude squared,
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// to save on one square root.
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void VadAudioProc::FindFirstSpectralPeaks(double* f_peak,
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size_t length_f_peak) {
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RTC_DCHECK_GE(length_f_peak, kNum10msSubframes);
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double lpc[kNum10msSubframes * (kLpcOrder + 1)];
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// For all sub-frames.
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GetLpcPolynomials(lpc, kNum10msSubframes * (kLpcOrder + 1));
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const size_t kNumDftCoefficients = kDftSize / 2 + 1;
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float data[kDftSize];
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for (size_t i = 0; i < kNum10msSubframes; i++) {
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// Convert to float with zero pad.
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memset(data, 0, sizeof(data));
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for (size_t n = 0; n < kLpcOrder + 1; n++) {
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data[n] = static_cast<float>(lpc[i * (kLpcOrder + 1) + n]);
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}
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// Transform to frequency domain.
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WebRtc_rdft(kDftSize, 1, data, ip_, w_fft_);
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size_t index_peak = 0;
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float prev_magn_sqr = data[0] * data[0];
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float curr_magn_sqr = data[2] * data[2] + data[3] * data[3];
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float next_magn_sqr;
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bool found_peak = false;
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for (size_t n = 2; n < kNumDftCoefficients - 1; n++) {
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next_magn_sqr =
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data[2 * n] * data[2 * n] + data[2 * n + 1] * data[2 * n + 1];
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if (curr_magn_sqr < prev_magn_sqr && curr_magn_sqr < next_magn_sqr) {
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found_peak = true;
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index_peak = n - 1;
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break;
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}
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prev_magn_sqr = curr_magn_sqr;
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curr_magn_sqr = next_magn_sqr;
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}
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float fractional_index = 0;
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if (!found_peak) {
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// Checking if |kNumDftCoefficients - 1| is the local minimum.
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next_magn_sqr = data[1] * data[1];
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if (curr_magn_sqr < prev_magn_sqr && curr_magn_sqr < next_magn_sqr) {
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index_peak = kNumDftCoefficients - 1;
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}
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} else {
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// A peak is found, do a simple quadratic interpolation to get a more
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// accurate estimate of the peak location.
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fractional_index =
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QuadraticInterpolation(prev_magn_sqr, curr_magn_sqr, next_magn_sqr);
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}
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f_peak[i] = (index_peak + fractional_index) * kFrequencyResolution;
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}
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}
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// Using iSAC functions to estimate pitch gains & lags.
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void VadAudioProc::PitchAnalysis(double* log_pitch_gains,
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double* pitch_lags_hz,
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size_t length) {
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// TODO(turajs): This can be "imported" from iSAC & and the next two
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// constants.
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RTC_DCHECK_GE(length, kNum10msSubframes);
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const int kNumPitchSubframes = 4;
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double gains[kNumPitchSubframes];
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double lags[kNumPitchSubframes];
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const int kNumSubbandFrameSamples = 240;
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const int kNumLookaheadSamples = 24;
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float lower[kNumSubbandFrameSamples];
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float upper[kNumSubbandFrameSamples];
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double lower_lookahead[kNumSubbandFrameSamples];
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double upper_lookahead[kNumSubbandFrameSamples];
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double lower_lookahead_pre_filter[kNumSubbandFrameSamples +
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kNumLookaheadSamples];
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// Split signal to lower and upper bands
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WebRtcIsac_SplitAndFilterFloat(&audio_buffer_[kNumPastSignalSamples], lower,
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upper, lower_lookahead, upper_lookahead,
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pre_filter_handle_.get());
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WebRtcIsac_PitchAnalysis(lower_lookahead, lower_lookahead_pre_filter,
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pitch_analysis_handle_.get(), lags, gains);
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// Lags are computed on lower-band signal with sampling rate half of the
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// input signal.
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GetSubframesPitchParameters(
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kSampleRateHz / 2, gains, lags, kNumPitchSubframes, kNum10msSubframes,
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&log_old_gain_, &old_lag_, log_pitch_gains, pitch_lags_hz);
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}
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void VadAudioProc::Rms(double* rms, size_t length_rms) {
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RTC_DCHECK_GE(length_rms, kNum10msSubframes);
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size_t offset = kNumPastSignalSamples;
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for (size_t i = 0; i < kNum10msSubframes; i++) {
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rms[i] = 0;
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for (size_t n = 0; n < kNumSubframeSamples; n++, offset++)
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rms[i] += audio_buffer_[offset] * audio_buffer_[offset];
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rms[i] = sqrt(rms[i] / kNumSubframeSamples);
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}
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}
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} // namespace webrtc
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