audio_utility.cc revision 5d1f7b1de12d16ceb2c938c56701a3e8bfa558f7 
1// Copyright 2014 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#include "media/cast/test/utility/audio_utility.h"
6
7#include "base/time/time.h"
8#include "media/base/audio_bus.h"
9#include "media/cast/cast_config.h"
10
11namespace media {
12namespace cast {
13
14TestAudioBusFactory::TestAudioBusFactory(int num_channels,
15                                         int sample_rate,
16                                         float sine_wave_frequency,
17                                         float volume)
18    : num_channels_(num_channels),
19      sample_rate_(sample_rate),
20      volume_(volume),
21      source_(num_channels, sine_wave_frequency, sample_rate) {
22  CHECK_LT(0, num_channels);
23  CHECK_LT(0, sample_rate);
24  CHECK_LE(0.0f, volume_);
25  CHECK_LE(volume_, 1.0f);
26}
27
28TestAudioBusFactory::~TestAudioBusFactory() {}
29
30scoped_ptr<AudioBus> TestAudioBusFactory::NextAudioBus(
31    const base::TimeDelta& duration) {
32  const int num_samples = static_cast<int>((sample_rate_ * duration) /
33                                           base::TimeDelta::FromSeconds(1));
34  scoped_ptr<AudioBus> bus(AudioBus::Create(num_channels_, num_samples));
35  source_.OnMoreData(bus.get(), AudioBuffersState());
36  bus->Scale(volume_);
37  return bus.Pass();
38}
39
40scoped_ptr<PcmAudioFrame> ToPcmAudioFrame(const AudioBus& audio_bus,
41                                          int sample_rate) {
42  scoped_ptr<PcmAudioFrame> audio_frame(new PcmAudioFrame());
43  audio_frame->channels = audio_bus.channels();
44  audio_frame->frequency = sample_rate;
45  audio_frame->samples.resize(audio_bus.channels() * audio_bus.frames());
46  audio_bus.ToInterleaved(audio_bus.frames(),
47                          sizeof(audio_frame->samples.front()),
48                          &audio_frame->samples.front());
49  return audio_frame.Pass();
50}
51
52int CountZeroCrossings(const std::vector<int16>& samples) {
53  // The sample values must pass beyond |kAmplitudeThreshold| on the opposite
54  // side of zero before a crossing will be counted.
55  const int kAmplitudeThreshold = 1000;  // Approx. 3% of max amplitude.
56
57  int count = 0;
58  std::vector<int16>::const_iterator i = samples.begin();
59  int16 last = 0;
60  for (; i != samples.end() && abs(last) < kAmplitudeThreshold; ++i)
61    last = *i;
62  for (; i != samples.end(); ++i) {
63    if (abs(*i) >= kAmplitudeThreshold && (last < 0) != (*i < 0)) {
64      ++count;
65      last = *i;
66    }
67  }
68  return count;
69}
70
71}  // namespace cast
72}  // namespace media
73