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0b489303d2
Bug: webrtc:12338 Change-Id: I85bff694dd2ead83c939c4d1945eff82e1296001 No-Presubmit: True Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/227161 Commit-Queue: Artem Titov <titovartem@webrtc.org> Reviewed-by: Harald Alvestrand <hta@webrtc.org> Cr-Commit-Position: refs/heads/master@{#34690}
100 lines
4.1 KiB
C++
100 lines
4.1 KiB
C++
/*
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* Copyright (c) 2018 The WebRTC project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#ifndef MODULES_AUDIO_PROCESSING_AGC2_RNN_VAD_SPECTRAL_FEATURES_INTERNAL_H_
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#define MODULES_AUDIO_PROCESSING_AGC2_RNN_VAD_SPECTRAL_FEATURES_INTERNAL_H_
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#include <stddef.h>
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#include <array>
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#include <vector>
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#include "api/array_view.h"
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#include "modules/audio_processing/agc2/rnn_vad/common.h"
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namespace webrtc {
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namespace rnn_vad {
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// At a sample rate of 24 kHz, the last 3 Opus bands are beyond the Nyquist
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// frequency. However, band #19 gets the contributions from band #18 because
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// of the symmetric triangular filter with peak response at 12 kHz.
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constexpr int kOpusBands24kHz = 20;
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static_assert(kOpusBands24kHz < kNumBands,
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"The number of bands at 24 kHz must be less than those defined "
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"in the Opus scale at 48 kHz.");
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// Number of FFT frequency bins covered by each band in the Opus scale at a
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// sample rate of 24 kHz for 20 ms frames.
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// Declared here for unit testing.
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constexpr std::array<int, kOpusBands24kHz - 1> GetOpusScaleNumBins24kHz20ms() {
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return {4, 4, 4, 4, 4, 4, 4, 4, 8, 8, 8, 8, 16, 16, 16, 24, 24, 32, 48};
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}
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// TODO(bugs.webrtc.org/10480): Move to a separate file.
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// Class to compute band-wise spectral features in the Opus perceptual scale
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// for 20 ms frames sampled at 24 kHz. The analysis methods apply triangular
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// filters with peak response at the each band boundary.
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class SpectralCorrelator {
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public:
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// Ctor.
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SpectralCorrelator();
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SpectralCorrelator(const SpectralCorrelator&) = delete;
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SpectralCorrelator& operator=(const SpectralCorrelator&) = delete;
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~SpectralCorrelator();
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// Computes the band-wise spectral auto-correlations.
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// `x` must:
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// - have size equal to `kFrameSize20ms24kHz`;
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// - be encoded as vectors of interleaved real-complex FFT coefficients
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// where x[1] = y[1] = 0 (the Nyquist frequency coefficient is omitted).
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void ComputeAutoCorrelation(
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rtc::ArrayView<const float> x,
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rtc::ArrayView<float, kOpusBands24kHz> auto_corr) const;
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// Computes the band-wise spectral cross-correlations.
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// `x` and `y` must:
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// - have size equal to `kFrameSize20ms24kHz`;
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// - be encoded as vectors of interleaved real-complex FFT coefficients where
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// x[1] = y[1] = 0 (the Nyquist frequency coefficient is omitted).
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void ComputeCrossCorrelation(
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rtc::ArrayView<const float> x,
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rtc::ArrayView<const float> y,
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rtc::ArrayView<float, kOpusBands24kHz> cross_corr) const;
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private:
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const std::vector<float> weights_; // Weights for each Fourier coefficient.
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};
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// TODO(bugs.webrtc.org/10480): Move to anonymous namespace in
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// spectral_features.cc. Given a vector of Opus-bands energy coefficients,
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// computes the log magnitude spectrum applying smoothing both over time and
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// over frequency. Declared here for unit testing.
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void ComputeSmoothedLogMagnitudeSpectrum(
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rtc::ArrayView<const float> bands_energy,
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rtc::ArrayView<float, kNumBands> log_bands_energy);
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// TODO(bugs.webrtc.org/10480): Move to anonymous namespace in
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// spectral_features.cc. Creates a DCT table for arrays having size equal to
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// `kNumBands`. Declared here for unit testing.
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std::array<float, kNumBands * kNumBands> ComputeDctTable();
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// TODO(bugs.webrtc.org/10480): Move to anonymous namespace in
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// spectral_features.cc. Computes DCT for `in` given a pre-computed DCT table.
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// In-place computation is not allowed and `out` can be smaller than `in` in
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// order to only compute the first DCT coefficients. Declared here for unit
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// testing.
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void ComputeDct(rtc::ArrayView<const float> in,
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rtc::ArrayView<const float, kNumBands * kNumBands> dct_table,
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rtc::ArrayView<float> out);
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} // namespace rnn_vad
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} // namespace webrtc
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#endif // MODULES_AUDIO_PROCESSING_AGC2_RNN_VAD_SPECTRAL_FEATURES_INTERNAL_H_
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