1 /*
2 * Copyright (c) 2013 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 // MSVC++ requires this to be set before any other includes to get M_PI.
12 #define _USE_MATH_DEFINES
13
14 #include "webrtc/common_audio/resampler/sinusoidal_linear_chirp_source.h"
15
16 #include <math.h>
17
18 namespace webrtc {
19
SinusoidalLinearChirpSource(int sample_rate,size_t samples,double max_frequency,double delay_samples)20 SinusoidalLinearChirpSource::SinusoidalLinearChirpSource(int sample_rate,
21 size_t samples,
22 double max_frequency,
23 double delay_samples)
24 : sample_rate_(sample_rate),
25 total_samples_(samples),
26 max_frequency_(max_frequency),
27 current_index_(0),
28 delay_samples_(delay_samples) {
29 // Chirp rate.
30 double duration = static_cast<double>(total_samples_) / sample_rate_;
31 k_ = (max_frequency_ - kMinFrequency) / duration;
32 }
33
Run(size_t frames,float * destination)34 void SinusoidalLinearChirpSource::Run(size_t frames, float* destination) {
35 for (size_t i = 0; i < frames; ++i, ++current_index_) {
36 // Filter out frequencies higher than Nyquist.
37 if (Frequency(current_index_) > 0.5 * sample_rate_) {
38 destination[i] = 0;
39 } else {
40 // Calculate time in seconds.
41 if (current_index_ < delay_samples_) {
42 destination[i] = 0;
43 } else {
44 // Sinusoidal linear chirp.
45 double t = (current_index_ - delay_samples_) / sample_rate_;
46 destination[i] =
47 sin(2 * M_PI * (kMinFrequency * t + (k_ / 2) * t * t));
48 }
49 }
50 }
51 }
52
Frequency(size_t position)53 double SinusoidalLinearChirpSource::Frequency(size_t position) {
54 return kMinFrequency + (position - delay_samples_) *
55 (max_frequency_ - kMinFrequency) / total_samples_;
56 }
57
58 } // namespace webrtc
59