modules/audio_processing/aec3/filter_analyzer.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/filter_analyzer.h"
#include <math.h>

#include <algorithm>
#include <array>
#include <numeric>

#include "modules/audio_processing/aec3/aec3_common.h"
#include "modules/audio_processing/aec3/render_buffer.h"
#include "modules/audio_processing/logging/apm_data_dumper.h"
#include "rtc_base/atomic_ops.h"
#include "rtc_base/checks.h"

namespace webrtc {
namespace {

size_t FindPeakIndex(rtc::ArrayView<const float> filter_time_domain,
                     size_t peak_index_in,
                     size_t start_sample,
                     size_t end_sample) {
  size_t peak_index_out = peak_index_in;
  float max_h2 =
      filter_time_domain[peak_index_out] * filter_time_domain[peak_index_out];
  for (size_t k = start_sample; k <= end_sample; ++k) {
    float tmp = filter_time_domain[k] * filter_time_domain[k];
    if (tmp > max_h2) {
      peak_index_out = k;
      max_h2 = tmp;
    }
  }

  return peak_index_out;
}

}  // namespace

int FilterAnalyzer::instance_count_ = 0;

FilterAnalyzer::FilterAnalyzer(const EchoCanceller3Config& config)
    : data_dumper_(
          new ApmDataDumper(rtc::AtomicOps::Increment(&instance_count_))),
      bounded_erl_(config.ep_strength.bounded_erl),
      default_gain_(config.ep_strength.default_gain),
      h_highpass_(GetTimeDomainLength(config.filter.main.length_blocks), 0.f),
      filter_length_blocks_(config.filter.main_initial.length_blocks),
      consistent_filter_detector_(config) {
  Reset();
}

FilterAnalyzer::~FilterAnalyzer() = default;

void FilterAnalyzer::Reset() {
  delay_blocks_ = 0;
  blocks_since_reset_ = 0;
  gain_ = default_gain_;
  peak_index_ = 0;
  ResetRegion();
  consistent_filter_detector_.Reset();
}

void FilterAnalyzer::Update(rtc::ArrayView<const float> filter_time_domain,
                            const RenderBuffer& render_buffer) {
  SetRegionToAnalyze(filter_time_domain);
  AnalyzeRegion(filter_time_domain, render_buffer);
}

void FilterAnalyzer::AnalyzeRegion(
    rtc::ArrayView<const float> filter_time_domain,
    const RenderBuffer& render_buffer) {
  RTC_DCHECK_LT(region_.start_sample_, filter_time_domain.size());
  RTC_DCHECK_LT(peak_index_, filter_time_domain.size());
  RTC_DCHECK_LT(region_.end_sample_, filter_time_domain.size());

  // Preprocess the filter to avoid issues with low-frequency components in the
  // filter.
  PreProcessFilter(filter_time_domain);
  data_dumper_->DumpRaw("aec3_linear_filter_processed_td", h_highpass_);

  RTC_DCHECK_EQ(h_highpass_.size(), filter_time_domain.size());

  peak_index_ = FindPeakIndex(h_highpass_, peak_index_, region_.start_sample_,
                              region_.end_sample_);
  delay_blocks_ = peak_index_ >> kBlockSizeLog2;
  UpdateFilterGain(h_highpass_, peak_index_);
  filter_length_blocks_ = filter_time_domain.size() * (1.f / kBlockSize);

  consistent_estimate_ = consistent_filter_detector_.Detect(
      h_highpass_, region_, render_buffer.Block(-delay_blocks_)[0], peak_index_,
      delay_blocks_);
}

void FilterAnalyzer::UpdateFilterGain(
    rtc::ArrayView<const float> filter_time_domain,
    size_t peak_index) {
  bool sufficient_time_to_converge =
      ++blocks_since_reset_ > 5 * kNumBlocksPerSecond;

  if (sufficient_time_to_converge && consistent_estimate_) {
    gain_ = fabsf(filter_time_domain[peak_index]);
  } else {
    if (gain_) {
      gain_ = std::max(gain_, fabsf(filter_time_domain[peak_index]));
    }
  }

  if (bounded_erl_ && gain_) {
    gain_ = std::max(gain_, 0.01f);
  }
}

void FilterAnalyzer::PreProcessFilter(
    rtc::ArrayView<const float> filter_time_domain) {
  RTC_DCHECK_GE(h_highpass_.capacity(), filter_time_domain.size());
  h_highpass_.resize(filter_time_domain.size());
  // Minimum phase high-pass filter with cutoff frequency at about 600 Hz.
  constexpr std::array<float, 3> h = {{0.7929742f, -0.36072128f, -0.47047766f}};

  std::fill(h_highpass_.begin() + region_.start_sample_,
            h_highpass_.begin() + region_.end_sample_ + 1, 0.f);
  for (size_t k = std::max(h.size() - 1, region_.start_sample_);
       k <= region_.end_sample_; ++k) {
    for (size_t j = 0; j < h.size(); ++j) {
      h_highpass_[k] += filter_time_domain[k - j] * h[j];
    }
  }
}

void FilterAnalyzer::ResetRegion() {
  region_.start_sample_ = 0;
  region_.end_sample_ = 0;
}

void FilterAnalyzer::SetRegionToAnalyze(
    rtc::ArrayView<const float> filter_time_domain) {
  constexpr size_t kNumberBlocksToUpdate = 1;
  auto& r = region_;
    r.start_sample_ =
        r.end_sample_ == filter_time_domain.size() - 1 ? 0 : r.end_sample_ + 1;
    r.end_sample_ =
        std::min(r.start_sample_ + kNumberBlocksToUpdate * kBlockSize - 1,
                 filter_time_domain.size() - 1);
}

FilterAnalyzer::ConsistentFilterDetector::ConsistentFilterDetector(
    const EchoCanceller3Config& config)
    : active_render_threshold_(config.render_levels.active_render_limit *
                               config.render_levels.active_render_limit *
                               kFftLengthBy2) {}

void FilterAnalyzer::ConsistentFilterDetector::Reset() {
  significant_peak_ = false;
  filter_floor_accum_ = 0.f;
  filter_secondary_peak_ = 0.f;
  filter_floor_low_limit_ = 0;
  filter_floor_high_limit_ = 0;
  consistent_estimate_counter_ = 0;
  consistent_delay_reference_ = -10;
}

bool FilterAnalyzer::ConsistentFilterDetector::Detect(
    rtc::ArrayView<const float> filter_to_analyze,
    const FilterRegion& region,
    rtc::ArrayView<const float> x_block,
    size_t peak_index,
    int delay_blocks) {
  if (region.start_sample_ == 0) {
    filter_floor_accum_ = 0.f;
    filter_secondary_peak_ = 0.f;
    filter_floor_low_limit_ = peak_index < 64 ? 0 : peak_index - 64;
    filter_floor_high_limit_ =
        peak_index > filter_to_analyze.size() - 129 ? 0 : peak_index + 128;
  }

  for (size_t k = region.start_sample_;
       k < std::min(region.end_sample_ + 1, filter_floor_low_limit_); ++k) {
    float abs_h = fabsf(filter_to_analyze[k]);
    filter_floor_accum_ += abs_h;
    filter_secondary_peak_ = std::max(filter_secondary_peak_, abs_h);
  }

  for (size_t k = std::max(filter_floor_high_limit_, region.start_sample_);
       k <= region.end_sample_; ++k) {
    float abs_h = fabsf(filter_to_analyze[k]);
    filter_floor_accum_ += abs_h;
    filter_secondary_peak_ = std::max(filter_secondary_peak_, abs_h);
  }

  if (region.end_sample_ == filter_to_analyze.size() - 1) {
    float filter_floor = filter_floor_accum_ /
                         (filter_floor_low_limit_ + filter_to_analyze.size() -
                          filter_floor_high_limit_);

    float abs_peak = fabsf(filter_to_analyze[peak_index]);
    significant_peak_ = abs_peak > 10.f * filter_floor &&
                        abs_peak > 2.f * filter_secondary_peak_;
  }

  if (significant_peak_) {
    const float x_energy = std::inner_product(x_block.begin(), x_block.end(),
                                              x_block.begin(), 0.f);
    const bool active_render_block = x_energy > active_render_threshold_;

    if (consistent_delay_reference_ == delay_blocks) {
      if (active_render_block) {
        ++consistent_estimate_counter_;
      }
    } else {
      consistent_estimate_counter_ = 0;
      consistent_delay_reference_ = delay_blocks;
    }
  }
  return consistent_estimate_counter_ > 1.5f * kNumBlocksPerSecond;
}

}  // namespace webrtc