chromium/third_party/webrtc/modules/audio_processing/vad/pitch_internal.cc

/*
 *  Copyright (c) 2012 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/vad/pitch_internal.h"

#include <cmath>

namespace webrtc {

// A 4-to-3 linear interpolation.
// The interpolation constants are derived as following:
// Input pitch parameters are updated every 7.5 ms. Within a 30-ms interval
// we are interested in pitch parameters of 0-5 ms, 10-15ms and 20-25ms. This is
// like interpolating 4-to-6 and keep the odd samples.
// The reason behind this is that LPC coefficients are computed for the first
// half of each 10ms interval.
static void PitchInterpolation(double old_val, const double* in, double* out) { … }

void GetSubframesPitchParameters(int sampling_rate_hz,
                                 double* gains,
                                 double* lags,
                                 int num_in_frames,
                                 int num_out_frames,
                                 double* log_old_gain,
                                 double* old_lag,
                                 double* log_pitch_gain,
                                 double* pitch_lag_hz) { … }

}  // namespace webrtc