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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_STATIONARITY_ESTIMATOR_H_
#define MODULES_AUDIO_PROCESSING_AEC3_STATIONARITY_ESTIMATOR_H_
#include <stddef.h>
#include <array>
#include <atomic>
#include <memory>
#include "api/array_view.h"
#include "modules/audio_processing/aec3/aec3_common.h" // kFftLengthBy2Plus1...
#include "modules/audio_processing/aec3/reverb_model.h"
#include "rtc_base/checks.h"
namespace webrtc {
class ApmDataDumper;
struct SpectrumBuffer;
class StationarityEstimator {
public:
StationarityEstimator();
~StationarityEstimator();
// Reset the stationarity estimator.
void Reset();
// Update just the noise estimator. Usefull until the delay is known
void UpdateNoiseEstimator(
ArrayView<const std::array<float, kFftLengthBy2Plus1>> spectrum);
// Update the flag indicating whether this current frame is stationary. For
// getting a more robust estimation, it looks at future and/or past frames.
void UpdateStationarityFlags(
const SpectrumBuffer& spectrum_buffer,
ArrayView<const float> render_reverb_contribution_spectrum,
int idx_current,
int num_lookahead);
// Returns true if the current band is stationary.
bool IsBandStationary(size_t band) const {
return stationarity_flags_[band] && (hangovers_[band] == 0);
}
// Returns true if the current block is estimated as stationary.
bool IsBlockStationary() const;
private:
static constexpr int kWindowLength = 13;
// Returns the power of the stationary noise spectrum at a band.
float GetStationarityPowerBand(size_t k) const { return noise_.Power(k); }
// Get an estimation of the stationarity for the current band by looking
// at the past/present/future available data.
bool EstimateBandStationarity(const SpectrumBuffer& spectrum_buffer,
ArrayView<const float> average_reverb,
const std::array<int, kWindowLength>& indexes,
size_t band) const;
// True if all bands at the current point are stationary.
bool AreAllBandsStationary();
// Update the hangover depending on the stationary status of the current
// frame.
void UpdateHangover();
// Smooth the stationarity detection by looking at neighbouring frequency
// bands.
void SmoothStationaryPerFreq();
class NoiseSpectrum {
public:
NoiseSpectrum();
~NoiseSpectrum();
// Reset the noise power spectrum estimate state.
void Reset();
// Update the noise power spectrum with a new frame.
void Update(
ArrayView<const std::array<float, kFftLengthBy2Plus1>> spectrum);
// Get the noise estimation power spectrum.
ArrayView<const float> Spectrum() const { return noise_spectrum_; }
// Get the noise power spectrum at a certain band.
float Power(size_t band) const {
RTC_DCHECK_LT(band, noise_spectrum_.size());
return noise_spectrum_[band];
}
private:
// Get the update coefficient to be used for the current frame.
float GetAlpha() const;
// Update the noise power spectrum at a certain band with a new frame.
float UpdateBandBySmoothing(float power_band,
float power_band_noise,
float alpha) const;
std::array<float, kFftLengthBy2Plus1> noise_spectrum_;
size_t block_counter_;
};
static std::atomic<int> instance_count_;
std::unique_ptr<ApmDataDumper> data_dumper_;
NoiseSpectrum noise_;
std::array<int, kFftLengthBy2Plus1> hangovers_;
std::array<bool, kFftLengthBy2Plus1> stationarity_flags_;
};
} // namespace webrtc
#endif // MODULES_AUDIO_PROCESSING_AEC3_STATIONARITY_ESTIMATOR_H_
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