modules/audio_processing/aec3/subtractor.cc

/*
 *  Copyright (c) 2017 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/aec3/subtractor.h"

#include <algorithm>
#include <numeric>

#include "api/array_view.h"
#include "modules/audio_processing/logging/apm_data_dumper.h"
#include "rtc_base/checks.h"
#include "rtc_base/safe_minmax.h"

namespace webrtc {

namespace {

void PredictionError(const Aec3Fft& fft,
                     const FftData& S,
                     rtc::ArrayView<const float> y,
                     std::array<float, kBlockSize>* e,
                     FftData* E,
                     std::array<float, kBlockSize>* s) {
  std::array<float, kFftLength> s_scratch;
  fft.Ifft(S, &s_scratch);
  constexpr float kScale = 1.0f / kFftLengthBy2;
  std::transform(y.begin(), y.end(), s_scratch.begin() + kFftLengthBy2,
                 e->begin(), [&](float a, float b) { return a - b * kScale; });
  std::for_each(e->begin(), e->end(),
                [](float& a) { a = rtc::SafeClamp(a, -32768.f, 32767.f); });
  fft.ZeroPaddedFft(*e, E);

  if (s) {
    for (size_t k = 0; k < s->size(); ++k) {
      (*s)[k] = kScale * s_scratch[k + kFftLengthBy2];
    }
  }
}
}  // namespace

Subtractor::Subtractor(ApmDataDumper* data_dumper,
                       Aec3Optimization optimization)
    : fft_(),
      data_dumper_(data_dumper),
      optimization_(optimization),
      main_filter_(kAdaptiveFilterLength, optimization, data_dumper_),
      shadow_filter_(kAdaptiveFilterLength, optimization, data_dumper_) {
  RTC_DCHECK(data_dumper_);
}

Subtractor::~Subtractor() = default;

void Subtractor::HandleEchoPathChange(
    const EchoPathVariability& echo_path_variability) {
  use_shadow_filter_frequency_response_ = false;
  if (echo_path_variability.delay_change) {
    main_filter_.HandleEchoPathChange();
    shadow_filter_.HandleEchoPathChange();
    G_main_.HandleEchoPathChange();
    G_shadow_.HandleEchoPathChange();
    converged_filter_ = false;
    converged_filter_counter_ = 0;
  }
}

void Subtractor::Process(const RenderBuffer& render_buffer,
                         const rtc::ArrayView<const float> capture,
                         const RenderSignalAnalyzer& render_signal_analyzer,
                         const AecState& aec_state,
                         SubtractorOutput* output) {
  RTC_DCHECK_EQ(kBlockSize, capture.size());
  rtc::ArrayView<const float> y = capture;
  FftData& E_main = output->E_main;
  FftData E_shadow;
  std::array<float, kBlockSize>& e_main = output->e_main;
  std::array<float, kBlockSize>& e_shadow = output->e_shadow;

  FftData S;
  FftData& G = S;

  // Form the output of the main filter.
  main_filter_.Filter(render_buffer, &S);
  PredictionError(fft_, S, y, &e_main, &E_main, &output->s_main);

  // Form the output of the shadow filter.
  shadow_filter_.Filter(render_buffer, &S);
  PredictionError(fft_, S, y, &e_shadow, &E_shadow, nullptr);

  // Determine which frequency response should be used.
  const auto sum_of_squares = [](float a, float b) { return a + b * b; };
  const float e2_main =
      std::accumulate(e_main.begin(), e_main.end(), 0.f, sum_of_squares);
  const float e2_shadow =
      std::accumulate(e_shadow.begin(), e_shadow.end(), 0.f, sum_of_squares);
  const float y2 = std::accumulate(y.begin(), y.end(), 0.f, sum_of_squares);

  if (e2_main < e2_shadow && e2_main < 0.1 * y2) {
    use_shadow_filter_frequency_response_ = false;
  } else if (e2_shadow < e2_main && e2_shadow < 0.01 * y2) {
    use_shadow_filter_frequency_response_ = true;
  }

  // Flag whether the filter has at some point converged.
  // TODO(peah): Consider using a timeout for this.
  if (!converged_filter_) {
    if (y2 > kBlockSize * 100.f * 100.f) {
      if (e2_main < 0.3 * y2) {
        converged_filter_ = (++converged_filter_counter_) > 10;
      } else {
        converged_filter_counter_ = 0;
      }
    }
  }

  // Compute spectra for future use.
  E_main.Spectrum(optimization_, &output->E2_main);
  E_shadow.Spectrum(optimization_, &output->E2_shadow);

  // Update the main filter.
  G_main_.Compute(render_buffer, render_signal_analyzer, *output, main_filter_,
                  aec_state.SaturatedCapture(), &G);
  main_filter_.Adapt(render_buffer, G);
  data_dumper_->DumpRaw("aec3_subtractor_G_main", G.re);
  data_dumper_->DumpRaw("aec3_subtractor_G_main", G.im);

  // Update the shadow filter.
  G_shadow_.Compute(render_buffer, render_signal_analyzer, E_shadow,
                    shadow_filter_.SizePartitions(),
                    aec_state.SaturatedCapture(), &G);
  shadow_filter_.Adapt(render_buffer, G);

  data_dumper_->DumpRaw("aec3_subtractor_G_shadow", G.re);
  data_dumper_->DumpRaw("aec3_subtractor_G_shadow", G.im);

  main_filter_.DumpFilter("aec3_subtractor_H_main");
  shadow_filter_.DumpFilter("aec3_subtractor_H_shadow");
}

}  // namespace webrtc