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
18namespace webrtc {
19
20SinusoidalLinearChirpSource::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
34void 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
53double SinusoidalLinearChirpSource::Frequency(size_t position) {
54  return kMinFrequency + (position - delay_samples_) *
55      (max_frequency_ - kMinFrequency) / total_samples_;
56}
57
58}  // namespace webrtc
59