modules/audio_processing/agc2/noise_spectrum_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_spectrum_estimator.h"

#include <string.h>
#include <algorithm>

#include "api/array_view.h"
#include "modules/audio_processing/logging/apm_data_dumper.h"
#include "rtc_base/arraysize.h"

namespace webrtc {
namespace {
constexpr float kMinNoisePower = 100.f;
}  // namespace

NoiseSpectrumEstimator::NoiseSpectrumEstimator(ApmDataDumper* data_dumper)
    : data_dumper_(data_dumper) {
  Initialize();
}

void NoiseSpectrumEstimator::Initialize() {
  std::fill(noise_spectrum_, noise_spectrum_ + arraysize(noise_spectrum_),
            kMinNoisePower);
}

void NoiseSpectrumEstimator::Update(rtc::ArrayView<const float> spectrum,
                                    bool first_update) {
  RTC_DCHECK_EQ(65, spectrum.size());

  if (first_update) {
    // Initialize the noise spectral estimate with the signal spectrum.
    std::copy(spectrum.data(), spectrum.data() + spectrum.size(),
              noise_spectrum_);
  } else {
    // Smoothly update the noise spectral estimate towards the signal spectrum
    // such that the magnitude of the updates are limited.
    for (size_t k = 0; k < spectrum.size(); ++k) {
      if (noise_spectrum_[k] < spectrum[k]) {
        noise_spectrum_[k] = std::min(
            1.01f * noise_spectrum_[k],
            noise_spectrum_[k] + 0.05f * (spectrum[k] - noise_spectrum_[k]));
      } else {
        noise_spectrum_[k] = std::max(
            0.99f * noise_spectrum_[k],
            noise_spectrum_[k] + 0.05f * (spectrum[k] - noise_spectrum_[k]));
      }
    }
  }

  // Ensure that the noise spectal estimate does not become too low.
  for (auto& v : noise_spectrum_) {
    v = std::max(v, kMinNoisePower);
  }

  data_dumper_->DumpRaw("lc_noise_spectrum", 65, noise_spectrum_);
  data_dumper_->DumpRaw("lc_signal_spectrum", spectrum);
}

}  // namespace webrtc