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Side by Side Diff: webrtc/modules/audio_processing/agc/pitch_internal.cc

Issue 1212543002: Pull the Voice Activity Detector out from the AGC (Closed) Base URL: https://chromium.googlesource.com/external/webrtc.git@master
Patch Set: Created 5 years, 6 months ago
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1 /*
2 * Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
3 *
4 * Use of this source code is governed by a BSD-style license
5 * that can be found in the LICENSE file in the root of the source
6 * tree. An additional intellectual property rights grant can be found
7 * in the file PATENTS. All contributing project authors may
8 * be found in the AUTHORS file in the root of the source tree.
9 */
10
11 #include "webrtc/modules/audio_processing/agc/pitch_internal.h"
12
13 #include <cmath>
14
15 // A 4-to-3 linear interpolation.
16 // The interpolation constants are derived as following:
17 // Input pitch parameters are updated every 7.5 ms. Within a 30-ms interval
18 // we are interested in pitch parameters of 0-5 ms, 10-15ms and 20-25ms. This is
19 // like interpolating 4-to-6 and keep the odd samples.
20 // The reason behind this is that LPC coefficients are computed for the first
21 // half of each 10ms interval.
22 static void PitchInterpolation(double old_val, const double* in, double* out) {
23 out[0] = 1. / 6. * old_val + 5. / 6. * in[0];
24 out[1] = 5. / 6. * in[1] + 1. / 6. * in[2];
25 out[2] = 0.5 * in[2] + 0.5 * in[3];
26 }
27
28
29 void GetSubframesPitchParameters(int sampling_rate_hz,
30 double* gains,
31 double* lags,
32 int num_in_frames,
33 int num_out_frames,
34 double* log_old_gain,
35 double* old_lag,
36 double* log_pitch_gain,
37 double* pitch_lag_hz) {
38 // Gain interpolation is in log-domain, also returned in log-domain.
39 for (int n = 0; n < num_in_frames; n++)
40 gains[n] = log(gains[n] + 1e-12);
41
42 // Interpolate lags and gains.
43 PitchInterpolation(*log_old_gain, gains, log_pitch_gain);
44 *log_old_gain = gains[num_in_frames - 1];
45 PitchInterpolation(*old_lag, lags, pitch_lag_hz);
46 *old_lag = lags[num_in_frames - 1];
47
48 // Convert pitch-lags to Hertz.
49 for (int n = 0; n < num_out_frames; n++) {
50 pitch_lag_hz[n] = (sampling_rate_hz) / (pitch_lag_hz[n]);
51 }
52 }
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