media/filters/null_audio_renderer.h

   1 // Copyright (c) 2011 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 #ifndef MEDIA_FILTERS_NULL_AUDIO_RENDERER_H_
   6 #define MEDIA_FILTERS_NULL_AUDIO_RENDERER_H_
   7
   8 // NullAudioRenderer effectively uses an extra thread to "throw away" the
   9 // audio data at a rate resembling normal playback speed.  It's just like
  10 // decoding to /dev/null!
  11 //
  12 // NullAudioRenderer can also be used in situations where the client has no
  13 // audio device or we haven't written an audio implementation for a particular
  14 // platform yet.
  15
  16 #include <deque>
  17
  18 #include "base/memory/scoped_ptr.h"
  19 #include "base/threading/platform_thread.h"
  20 #include "media/base/buffers.h"
  21 #include "media/base/filters.h"
  22 #include "media/filters/audio_renderer_base.h"
  23
  24 namespace media {
  25
  26 class MEDIA_EXPORT NullAudioRenderer
  27     : public AudioRendererBase,
  28       public base::PlatformThread::Delegate {
  29  public:
  30   NullAudioRenderer();
  31   virtual ~NullAudioRenderer();
  32
  33   // AudioRenderer implementation.
  34   virtual void SetVolume(float volume);
  35
  36   // PlatformThread::Delegate implementation.
  37   virtual void ThreadMain();
  38
  39  protected:
  40   // AudioRendererBase implementation.
  41   virtual bool OnInitialize(int bits_per_channel,
  42                             ChannelLayout channel_layout,
  43                             int sample_rate);
  44   virtual void OnStop();
  45
  46  private:
  47   // A number to convert bytes written in FillBuffer to milliseconds based on
  48   // the audio format.
  49   size_t bytes_per_millisecond_;
  50
  51   // A buffer passed to FillBuffer to advance playback.
  52   scoped_array<uint8> buffer_;
  53   size_t buffer_size_;
  54
  55   // Separate thread used to throw away data.
  56   base::PlatformThreadHandle thread_;
  57
  58   // Shutdown flag.
  59   bool shutdown_;
  60
  61   DISALLOW_COPY_AND_ASSIGN(NullAudioRenderer);
  62 };
  63
  64 }  // namespace media
  65
  66 #endif  // MEDIA_FILTERS_NULL_AUDIO_RENDERER_H_