media/audio/simple_sources.cc

   1 // Copyright (c) 2012 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 // MSVC++ requires this to be set before any other includes to get M_PI.
   5 #define _USE_MATH_DEFINES
   6 #include <cmath>
   7
   8 #include "media/audio/simple_sources.h"
   9
  10 #include <algorithm>
  11
  12 #include "base/logging.h"
  13
  14 namespace media {
  15
  16 //////////////////////////////////////////////////////////////////////////////
  17 // SineWaveAudioSource implementation.
  18
  19 SineWaveAudioSource::SineWaveAudioSource(int channels,
  20                                          double freq, double sample_freq)
  21     : channels_(channels),
  22       f_(freq / sample_freq),
  23       time_state_(0),
  24       cap_(0),
  25       callbacks_(0),
  26       errors_(0) {
  27 }
  28
  29 // The implementation could be more efficient if a lookup table is constructed
  30 // but it is efficient enough for our simple needs.
  31 int SineWaveAudioSource::OnMoreData(AudioBus* audio_bus,
  32                                     AudioBuffersState audio_buffers) {
  33   base::AutoLock auto_lock(time_lock_);
  34   callbacks_++;
  35
  36   // The table is filled with s(t) = kint16max*sin(Theta*t),
  37   // where Theta = 2*PI*fs.
  38   // We store the discrete time value |t| in a member to ensure that the
  39   // next pass starts at a correct state.
  40   int max_frames = cap_ > 0 ?
  41       std::min(audio_bus->frames(), cap_ - time_state_) : audio_bus->frames();
  42   for (int i = 0; i < max_frames; ++i)
  43     audio_bus->channel(0)[i] = sin(2.0 * M_PI * f_ * time_state_++);
  44   for (int i = 1; i < audio_bus->channels(); ++i) {
  45     memcpy(audio_bus->channel(i), audio_bus->channel(0),
  46            max_frames * sizeof(*audio_bus->channel(i)));
  47   }
  48   return max_frames;
  49 }
  50
  51 void SineWaveAudioSource::OnError(AudioOutputStream* stream) {
  52   errors_++;
  53 }
  54
  55 void SineWaveAudioSource::CapSamples(int cap) {
  56   base::AutoLock auto_lock(time_lock_);
  57   DCHECK_GT(cap, 0);
  58   cap_ = cap;
  59 }
  60
  61 void SineWaveAudioSource::Reset() {
  62   base::AutoLock auto_lock(time_lock_);
  63   time_state_ = 0;
  64 }
  65
  66 }  // namespace media