chromium/third_party/webrtc/modules/audio_processing/agc2/noise_level_estimator.cc

/*
 *  Copyright (c) 2016 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/agc2/noise_level_estimator.h"

#include <stddef.h>

#include <algorithm>
#include <cmath>
#include <numeric>

#include "api/audio/audio_view.h"
#include "modules/audio_processing/logging/apm_data_dumper.h"
#include "rtc_base/checks.h"

namespace webrtc {
namespace {

constexpr int kFramesPerSecond = …;

float FrameEnergy(DeinterleavedView<const float> audio) { … }

float EnergyToDbfs(float signal_energy, int num_samples) { … }

// Updates the noise floor with instant decay and slow attack. This tuning is
// specific for AGC2, so that (i) it can promptly increase the gain if the noise
// floor drops (instant decay) and (ii) in case of music or fast speech, due to
// which the noise floor can be overestimated, the gain reduction is slowed
// down.
float SmoothNoiseFloorEstimate(float current_estimate, float new_estimate) { … }

class NoiseFloorEstimator : public NoiseLevelEstimator { … };

}  // namespace

std::unique_ptr<NoiseLevelEstimator> CreateNoiseFloorEstimator(
    ApmDataDumper* data_dumper) { … }

}  // namespace webrtc