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 #include "media/audio/audio_util.h"
  14
  15 namespace media {
  16
  17 //////////////////////////////////////////////////////////////////////////////
  18 // SineWaveAudioSource implementation.
  19
  20 SineWaveAudioSource::SineWaveAudioSource(int channels,
  21                                          double freq, double sample_freq)
  22     : channels_(channels),
  23       f_(freq / sample_freq),
  24       time_state_(0),
  25       cap_(0),
  26       callbacks_(0),
  27       errors_(0) {
  28 }
  29
  30 // The implementation could be more efficient if a lookup table is constructed
  31 // but it is efficient enough for our simple needs.
  32 int SineWaveAudioSource::OnMoreData(AudioBus* audio_bus,
  33                                     AudioBuffersState audio_buffers) {
  34   base::AutoLock auto_lock(time_lock_);
  35   callbacks_++;
  36
  37   // The table is filled with s(t) = kint16max*sin(Theta*t),
  38   // where Theta = 2*PI*fs.
  39   // We store the discrete time value |t| in a member to ensure that the
  40   // next pass starts at a correct state.
  41   int max_frames = cap_ > 0 ?
  42       std::min(audio_bus->frames(), cap_ - time_state_) : audio_bus->frames();
  43   for (int i = 0; i < max_frames; ++i)
  44     audio_bus->channel(0)[i] = sin(2.0 * M_PI * f_ * time_state_++);
  45   for (int i = 1; i < audio_bus->channels(); ++i) {
  46     memcpy(audio_bus->channel(i), audio_bus->channel(0),
  47            max_frames * sizeof(*audio_bus->channel(i)));
  48   }
  49   return max_frames;
  50 }
  51
  52 int SineWaveAudioSource::OnMoreIOData(AudioBus* source,
  53                                       AudioBus* dest,
  54                                       AudioBuffersState audio_buffers) {
  55   return OnMoreData(dest, audio_buffers);
  56 }
  57
  58 void SineWaveAudioSource::OnError(AudioOutputStream* stream) {
  59   errors_++;
  60 }
  61
  62 void SineWaveAudioSource::CapSamples(int cap) {
  63   base::AutoLock auto_lock(time_lock_);
  64   DCHECK_GT(cap, 0);
  65   cap_ = cap;
  66 }
  67
  68 void SineWaveAudioSource::Reset() {
  69   base::AutoLock auto_lock(time_lock_);
  70   time_state_ = 0;
  71 }
  72
  73 }  // namespace media