reverb_decay_estimator.h

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/*

 *  Copyright (c) 2018 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.

*/

#ifndef MODULES_AUDIO_PROCESSING_AEC3_REVERB_DECAY_ESTIMATOR_H_

#define MODULES_AUDIO_PROCESSING_AEC3_REVERB_DECAY_ESTIMATOR_H_

#include <array>

#include <optional>

#include <vector>

#include "api/array_view.h"

#include "modules/audio_processing/aec3/aec3_common.h"  // kMaxAdaptiveFilter...

namespace webrtc {

class ApmDataDumper;

struct EchoCanceller3Config;

// Class for estimating the decay of the late reverb.

class ReverbDecayEstimator {

 public:

  explicit ReverbDecayEstimator(const EchoCanceller3Config& config);

  ~ReverbDecayEstimator();

  // Updates the decay estimate.

  void Update(rtc::ArrayView<const float> filter,

              const std::optional<float>& filter_quality,

              int filter_delay_blocks,

              bool usable_linear_filter,

              bool stationary_signal);

  // Returns the decay for the exponential model. The parameter `mild` indicates

  // which exponential decay to return, the default one or a milder one.

  float Decay(bool mild) const {

    if (use_adaptive_echo_decay_) {

      return decay_;

    } else {

      return mild ? mild_decay_ : decay_;

  // Dumps debug data.

  void Dump(ApmDataDumper* data_dumper) const;

 private:

  void EstimateDecay(rtc::ArrayView<const float> filter, int peak_block);

  void AnalyzeFilter(rtc::ArrayView<const float> filter);

  void ResetDecayEstimation();

  // Class for estimating the decay of the late reverb from the linear filter.

  class LateReverbLinearRegressor {

   public:

    // Resets the estimator to receive a specified number of data points.

    void Reset(int num_data_points);

    // Accumulates estimation data.

    void Accumulate(float z);

    // Estimates the decay.

    float Estimate();

    // Returns whether an estimate is available.

    bool EstimateAvailable() const { return n_ == N_ && N_ != 0; }

   public:

    float nz_ = 0.f;

    float nn_ = 0.f;

    float count_ = 0.f;

    int N_ = 0;

    int n_ = 0;

};

  // Class for identifying the length of the early reverb from the linear

  // filter. For identifying the early reverberations, the impulse response is

  // divided in sections and the tilt of each section is computed by a linear

  // regressor.

  class EarlyReverbLengthEstimator {

   public:

    explicit EarlyReverbLengthEstimator(int max_blocks);

    ~EarlyReverbLengthEstimator();

    // Resets the estimator.

    void Reset();

    // Accumulates estimation data.

    void Accumulate(float value, float smoothing);

    // Estimates the size in blocks of the early reverb.

    int Estimate();

    // Dumps debug data.

    void Dump(ApmDataDumper* data_dumper) const;

   private:

    std::vector<float> numerators_smooth_;

    std::vector<float> numerators_;

    int coefficients_counter_;

    int block_counter_ = 0;

    int n_sections_ = 0;

};

  const int filter_length_blocks_;

  const int filter_length_coefficients_;

  const bool use_adaptive_echo_decay_;

  LateReverbLinearRegressor late_reverb_decay_estimator_;

  EarlyReverbLengthEstimator early_reverb_estimator_;

  int late_reverb_start_;

  int late_reverb_end_;

  int block_to_analyze_ = 0;

  int estimation_region_candidate_size_ = 0;

  bool estimation_region_identified_ = false;

  std::vector<float> previous_gains_;

  float decay_;

  float mild_decay_;

  float tail_gain_ = 0.f;

  float smoothing_constant_ = 0.f;

};

}  // namespace webrtc

#endif  // MODULES_AUDIO_PROCESSING_AEC3_REVERB_DECAY_ESTIMATOR_H_