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Diffstat (limited to 'third_party/libwebrtc/modules/audio_processing/agc2/rnn_vad/spectral_features_internal.h')
-rw-r--r-- | third_party/libwebrtc/modules/audio_processing/agc2/rnn_vad/spectral_features_internal.h | 100 |
1 files changed, 100 insertions, 0 deletions
diff --git a/third_party/libwebrtc/modules/audio_processing/agc2/rnn_vad/spectral_features_internal.h b/third_party/libwebrtc/modules/audio_processing/agc2/rnn_vad/spectral_features_internal.h new file mode 100644 index 0000000000..f4b293a567 --- /dev/null +++ b/third_party/libwebrtc/modules/audio_processing/agc2/rnn_vad/spectral_features_internal.h @@ -0,0 +1,100 @@ +/* + * 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_INTERNAL_H_ +#define MODULES_AUDIO_PROCESSING_AGC2_RNN_VAD_SPECTRAL_FEATURES_INTERNAL_H_ + +#include <stddef.h> + +#include <array> +#include <vector> + +#include "api/array_view.h" +#include "modules/audio_processing/agc2/rnn_vad/common.h" + +namespace webrtc { +namespace rnn_vad { + +// At a sample rate of 24 kHz, the last 3 Opus bands are beyond the Nyquist +// frequency. However, band #19 gets the contributions from band #18 because +// of the symmetric triangular filter with peak response at 12 kHz. +constexpr int kOpusBands24kHz = 20; +static_assert(kOpusBands24kHz < kNumBands, + "The number of bands at 24 kHz must be less than those defined " + "in the Opus scale at 48 kHz."); + +// Number of FFT frequency bins covered by each band in the Opus scale at a +// sample rate of 24 kHz for 20 ms frames. +// Declared here for unit testing. +constexpr std::array<int, kOpusBands24kHz - 1> GetOpusScaleNumBins24kHz20ms() { + return {4, 4, 4, 4, 4, 4, 4, 4, 8, 8, 8, 8, 16, 16, 16, 24, 24, 32, 48}; +} + +// TODO(bugs.webrtc.org/10480): Move to a separate file. +// Class to compute band-wise spectral features in the Opus perceptual scale +// for 20 ms frames sampled at 24 kHz. The analysis methods apply triangular +// filters with peak response at the each band boundary. +class SpectralCorrelator { + public: + // Ctor. + SpectralCorrelator(); + SpectralCorrelator(const SpectralCorrelator&) = delete; + SpectralCorrelator& operator=(const SpectralCorrelator&) = delete; + ~SpectralCorrelator(); + + // Computes the band-wise spectral auto-correlations. + // `x` must: + // - have size equal to `kFrameSize20ms24kHz`; + // - be encoded as vectors of interleaved real-complex FFT coefficients + // where x[1] = y[1] = 0 (the Nyquist frequency coefficient is omitted). + void ComputeAutoCorrelation( + rtc::ArrayView<const float> x, + rtc::ArrayView<float, kOpusBands24kHz> auto_corr) const; + + // Computes the band-wise spectral cross-correlations. + // `x` and `y` must: + // - have size equal to `kFrameSize20ms24kHz`; + // - be encoded as vectors of interleaved real-complex FFT coefficients where + // x[1] = y[1] = 0 (the Nyquist frequency coefficient is omitted). + void ComputeCrossCorrelation( + rtc::ArrayView<const float> x, + rtc::ArrayView<const float> y, + rtc::ArrayView<float, kOpusBands24kHz> cross_corr) const; + + private: + const std::vector<float> weights_; // Weights for each Fourier coefficient. +}; + +// TODO(bugs.webrtc.org/10480): Move to anonymous namespace in +// spectral_features.cc. Given a vector of Opus-bands energy coefficients, +// computes the log magnitude spectrum applying smoothing both over time and +// over frequency. Declared here for unit testing. +void ComputeSmoothedLogMagnitudeSpectrum( + rtc::ArrayView<const float> bands_energy, + rtc::ArrayView<float, kNumBands> log_bands_energy); + +// TODO(bugs.webrtc.org/10480): Move to anonymous namespace in +// spectral_features.cc. Creates a DCT table for arrays having size equal to +// `kNumBands`. Declared here for unit testing. +std::array<float, kNumBands * kNumBands> ComputeDctTable(); + +// TODO(bugs.webrtc.org/10480): Move to anonymous namespace in +// spectral_features.cc. Computes DCT for `in` given a pre-computed DCT table. +// In-place computation is not allowed and `out` can be smaller than `in` in +// order to only compute the first DCT coefficients. Declared here for unit +// testing. +void ComputeDct(rtc::ArrayView<const float> in, + rtc::ArrayView<const float, kNumBands * kNumBands> dct_table, + rtc::ArrayView<float> out); + +} // namespace rnn_vad +} // namespace webrtc + +#endif // MODULES_AUDIO_PROCESSING_AGC2_RNN_VAD_SPECTRAL_FEATURES_INTERNAL_H_ |