tor-browser

erl_estimator.cc (5125B)

---

/*
*  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/erl_estimator.h"

#include <algorithm>
#include <array>
#include <cstddef>
#include <iterator>
#include <numeric>
#include <vector>

#include "api/array_view.h"
#include "modules/audio_processing/aec3/aec3_common.h"
#include "rtc_base/checks.h"

namespace webrtc {

namespace {

constexpr float kMinErl = 0.01f;
constexpr float kMaxErl = 1000.f;

}  // namespace

ErlEstimator::ErlEstimator(size_t startup_phase_length_blocks_)
   : startup_phase_length_blocks__(startup_phase_length_blocks_) {
 erl_.fill(kMaxErl);
 hold_counters_.fill(0);
 erl_time_domain_ = kMaxErl;
 hold_counter_time_domain_ = 0;
}

ErlEstimator::~ErlEstimator() = default;

void ErlEstimator::Reset() {
 blocks_since_reset_ = 0;
}

void ErlEstimator::Update(
   const std::vector<bool>& converged_filters,
   ArrayView<const std::array<float, kFftLengthBy2Plus1>> render_spectra,
   ArrayView<const std::array<float, kFftLengthBy2Plus1>> capture_spectra) {
 const size_t num_capture_channels = converged_filters.size();
 RTC_DCHECK_EQ(capture_spectra.size(), num_capture_channels);

 // Corresponds to WGN of power -46 dBFS.
 constexpr float kX2Min = 44015068.0f;

 const auto first_converged_iter =
     std::find(converged_filters.begin(), converged_filters.end(), true);
 const bool any_filter_converged =
     first_converged_iter != converged_filters.end();

 if (++blocks_since_reset_ < startup_phase_length_blocks__ ||
     !any_filter_converged) {
   return;
 }

 // Use the maximum spectrum across capture and the maximum across render.
 std::array<float, kFftLengthBy2Plus1> max_capture_spectrum_data;
 std::array<float, kFftLengthBy2Plus1> max_capture_spectrum =
     capture_spectra[/*channel=*/0];
 if (num_capture_channels > 1) {
   // Initialize using the first channel with a converged filter.
   const size_t first_converged =
       std::distance(converged_filters.begin(), first_converged_iter);
   RTC_DCHECK_GE(first_converged, 0);
   RTC_DCHECK_LT(first_converged, num_capture_channels);
   max_capture_spectrum_data = capture_spectra[first_converged];

   for (size_t ch = first_converged + 1; ch < num_capture_channels; ++ch) {
     if (!converged_filters[ch]) {
       continue;
     }
     for (size_t k = 0; k < kFftLengthBy2Plus1; ++k) {
       max_capture_spectrum_data[k] =
           std::max(max_capture_spectrum_data[k], capture_spectra[ch][k]);
     }
   }
   max_capture_spectrum = max_capture_spectrum_data;
 }

 const size_t num_render_channels = render_spectra.size();
 std::array<float, kFftLengthBy2Plus1> max_render_spectrum_data;
 ArrayView<const float, kFftLengthBy2Plus1> max_render_spectrum =
     render_spectra[/*channel=*/0];
 if (num_render_channels > 1) {
   std::copy(render_spectra[0].begin(), render_spectra[0].end(),
             max_render_spectrum_data.begin());
   for (size_t ch = 1; ch < num_render_channels; ++ch) {
     for (size_t k = 0; k < kFftLengthBy2Plus1; ++k) {
       max_render_spectrum_data[k] =
           std::max(max_render_spectrum_data[k], render_spectra[ch][k]);
     }
   }
   max_render_spectrum = max_render_spectrum_data;
 }

 const auto& X2 = max_render_spectrum;
 const auto& Y2 = max_capture_spectrum;

 // Update the estimates in a maximum statistics manner.
 for (size_t k = 1; k < kFftLengthBy2; ++k) {
   if (X2[k] > kX2Min) {
     const float new_erl = Y2[k] / X2[k];
     if (new_erl < erl_[k]) {
       hold_counters_[k - 1] = 1000;
       erl_[k] += 0.1f * (new_erl - erl_[k]);
       erl_[k] = std::max(erl_[k], kMinErl);
     }
   }
 }

 std::for_each(hold_counters_.begin(), hold_counters_.end(),
               [](int& a) { --a; });
 std::transform(hold_counters_.begin(), hold_counters_.end(), erl_.begin() + 1,
                erl_.begin() + 1, [](int a, float b) {
                  return a > 0 ? b : std::min(kMaxErl, 2.f * b);
                });

 erl_[0] = erl_[1];
 erl_[kFftLengthBy2] = erl_[kFftLengthBy2 - 1];

 // Compute ERL over all frequency bins.
 const float X2_sum = std::accumulate(X2.begin(), X2.end(), 0.0f);

 if (X2_sum > kX2Min * X2.size()) {
   const float Y2_sum = std::accumulate(Y2.begin(), Y2.end(), 0.0f);
   const float new_erl = Y2_sum / X2_sum;
   if (new_erl < erl_time_domain_) {
     hold_counter_time_domain_ = 1000;
     erl_time_domain_ += 0.1f * (new_erl - erl_time_domain_);
     erl_time_domain_ = std::max(erl_time_domain_, kMinErl);
   }
 }

 --hold_counter_time_domain_;
 erl_time_domain_ = (hold_counter_time_domain_ > 0)
                        ? erl_time_domain_
                        : std::min(kMaxErl, 2.f * erl_time_domain_);
}

}  // namespace webrtc