spectral_features.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_AGC2_RNN_VAD_SPECTRAL_FEATURES_H_

#define MODULES_AUDIO_PROCESSING_AGC2_RNN_VAD_SPECTRAL_FEATURES_H_

#include <array>

#include <cstddef>

#include <memory>

#include <vector>

#include "api/array_view.h"

#include "modules/audio_processing/agc2/rnn_vad/common.h"

#include "modules/audio_processing/agc2/rnn_vad/ring_buffer.h"

#include "modules/audio_processing/agc2/rnn_vad/spectral_features_internal.h"

#include "modules/audio_processing/agc2/rnn_vad/symmetric_matrix_buffer.h"

#include "modules/audio_processing/utility/pffft_wrapper.h"

namespace webrtc {

namespace rnn_vad {

// Class to compute spectral features.

class SpectralFeaturesExtractor {

 public:

  SpectralFeaturesExtractor();

  SpectralFeaturesExtractor(const SpectralFeaturesExtractor&) = delete;

  SpectralFeaturesExtractor& operator=(const SpectralFeaturesExtractor&) =

      delete;

  ~SpectralFeaturesExtractor();

  // Resets the internal state of the feature extractor.

  void Reset();

  // Analyzes a pair of reference and lagged frames from the pitch buffer,

  // detects silence and computes features. If silence is detected, the output

  // is neither computed nor written.

  bool CheckSilenceComputeFeatures(

      rtc::ArrayView<const float, kFrameSize20ms24kHz> reference_frame,

      rtc::ArrayView<const float, kFrameSize20ms24kHz> lagged_frame,

      rtc::ArrayView<float, kNumBands - kNumLowerBands> higher_bands_cepstrum,

      rtc::ArrayView<float, kNumLowerBands> average,

      rtc::ArrayView<float, kNumLowerBands> first_derivative,

      rtc::ArrayView<float, kNumLowerBands> second_derivative,

      rtc::ArrayView<float, kNumLowerBands> bands_cross_corr,

      float* variability);

 private:

  void ComputeAvgAndDerivatives(

      rtc::ArrayView<float, kNumLowerBands> average,

      rtc::ArrayView<float, kNumLowerBands> first_derivative,

      rtc::ArrayView<float, kNumLowerBands> second_derivative) const;

  void ComputeNormalizedCepstralCorrelation(

      rtc::ArrayView<float, kNumLowerBands> bands_cross_corr);

  float ComputeVariability() const;

  const std::array<float, kFrameSize20ms24kHz / 2> half_window_;

  Pffft fft_;

  std::unique_ptr<Pffft::FloatBuffer> fft_buffer_;

  std::unique_ptr<Pffft::FloatBuffer> reference_frame_fft_;

  std::unique_ptr<Pffft::FloatBuffer> lagged_frame_fft_;

  SpectralCorrelator spectral_correlator_;

  std::array<float, kOpusBands24kHz> reference_frame_bands_energy_;

  std::array<float, kOpusBands24kHz> lagged_frame_bands_energy_;

  std::array<float, kOpusBands24kHz> bands_cross_corr_;

  const std::array<float, kNumBands * kNumBands> dct_table_;

  RingBuffer<float, kNumBands, kCepstralCoeffsHistorySize>

      cepstral_coeffs_ring_buf_;

  SymmetricMatrixBuffer<float, kCepstralCoeffsHistorySize> cepstral_diffs_buf_;

};

}  // namespace rnn_vad

}  // namespace webrtc

#endif  // MODULES_AUDIO_PROCESSING_AGC2_RNN_VAD_SPECTRAL_FEATURES_H_