text: // Copyright (c) 2012 The Chromium Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  #ifndef MEDIA_AUDIO_SIMPLE_SOURCES_H_
  #define MEDIA_AUDIO_SIMPLE_SOURCES_H_
  
  #include "base/synchronization/lock.h"
  #include "media/audio/audio_io.h"
  #include "media/base/seekable_buffer.h"
  
  namespace media {
  
  // An audio source that produces a pure sinusoidal tone.
  class MEDIA_EXPORT SineWaveAudioSource
      : public AudioOutputStream::AudioSourceCallback {
   public:
    // |channels| is the number of audio channels, |freq| is the frequency in
    // hertz and it has to be less than half of the sampling frequency
    // |sample_freq| or else you will get aliasing.
    SineWaveAudioSource(int channels, double freq, double sample_freq);
    virtual ~SineWaveAudioSource() {}
  
    // Return up to |cap| samples of data via OnMoreData().  Use Reset() to
    // allow more data to be served.
    void CapSamples(int cap);
    void Reset();
  
    // Implementation of AudioSourceCallback.
    virtual int OnMoreData(AudioBus* audio_bus,
                           AudioBuffersState audio_buffers) OVERRIDE;
    virtual int OnMoreIOData(AudioBus* source,
                             AudioBus* dest,
                             AudioBuffersState audio_buffers) OVERRIDE;
    virtual void OnError(AudioOutputStream* stream) OVERRIDE;
  
    // The number of OnMoreData()+OnMoreIOData() and OnError() calls respectively.
    int callbacks() { return callbacks_; }
    int errors() { return errors_; }
  
   protected:
    int channels_;
    double f_;
    int time_state_;
    int cap_;
    int callbacks_;
    int errors_;
    base::Lock time_lock_;
  };
  
  }  // namespace media
  
  #endif  // MEDIA_AUDIO_SIMPLE_SOURCES_H_
  