media/audio/audio_output_dispatcher.h

   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
   5 // AudioOutputDispatcher is a single-threaded base class that dispatches
   6 // creation and deletion of audio output streams. AudioOutputProxy objects use
   7 // this class to allocate and recycle actual audio output streams. When playback
   8 // is started, the proxy calls StartStream() to get an output stream that it
   9 // uses to play audio. When playback is stopped, the proxy returns the stream
  10 // back to the dispatcher by calling StopStream().
  11 //
  12 // AudioManagerBase creates one specialization of AudioOutputDispatcher on the
  13 // audio thread for each possible set of audio parameters. I.e streams with
  14 // different parameters are managed independently.  The AudioOutputDispatcher
  15 // instance is then deleted on the audio thread when the AudioManager shuts
  16 // down.
  17
  18 #ifndef MEDIA_AUDIO_AUDIO_OUTPUT_DISPATCHER_H_
  19 #define MEDIA_AUDIO_AUDIO_OUTPUT_DISPATCHER_H_
  20
  21 #include "base/basictypes.h"
  22 #include "base/memory/ref_counted.h"
  23 #include "base/timer/timer.h"
  24 #include "media/audio/audio_io.h"
  25 #include "media/audio/audio_manager.h"
  26 #include "media/audio/audio_parameters.h"
  27
  28 namespace base {
  29 class MessageLoopProxy;
  30 }
  31
  32 namespace media {
  33
  34 class AudioOutputProxy;
  35
  36 class MEDIA_EXPORT AudioOutputDispatcher
  37     : public base::RefCountedThreadSafe<AudioOutputDispatcher> {
  38  public:
  39   AudioOutputDispatcher(AudioManager* audio_manager,
  40                         const AudioParameters& params,
  41                         const std::string& output_device_id,
  42                         const std::string& input_device_id);
  43
  44   // Called by AudioOutputProxy to open the stream.
  45   // Returns false, if it fails to open it.
  46   virtual bool OpenStream() = 0;
  47
  48   // Called by AudioOutputProxy when the stream is started.
  49   // Uses |callback| to get source data and report errors, if any.
  50   // Does *not* take ownership of this callback.
  51   // Returns true if started successfully, false otherwise.
  52   virtual bool StartStream(AudioOutputStream::AudioSourceCallback* callback,
  53                            AudioOutputProxy* stream_proxy) = 0;
  54
  55   // Called by AudioOutputProxy when the stream is stopped.
  56   // Ownership of the |stream_proxy| is passed to the dispatcher.
  57   virtual void StopStream(AudioOutputProxy* stream_proxy) = 0;
  58
  59   // Called by AudioOutputProxy when the volume is set.
  60   virtual void StreamVolumeSet(AudioOutputProxy* stream_proxy,
  61                                double volume) = 0;
  62
  63   // Called by AudioOutputProxy when the stream is closed.
  64   virtual void CloseStream(AudioOutputProxy* stream_proxy) = 0;
  65
  66   // Called on the audio thread when the AudioManager is shutting down.
  67   virtual void Shutdown() = 0;
  68
  69   // Accessor to the input device id used by unified IO.
  70   const std::string& input_device_id() const { return input_device_id_; }
  71
  72  protected:
  73   friend class base::RefCountedThreadSafe<AudioOutputDispatcher>;
  74   friend class AudioOutputProxyTest;
  75
  76   virtual ~AudioOutputDispatcher();
  77
  78   // A no-reference-held pointer (we don't want circular references) back to the
  79   // AudioManager that owns this object.
  80   AudioManager* audio_manager_;
  81   const scoped_refptr<base::MessageLoopProxy> message_loop_;
  82   const AudioParameters params_;
  83   const std::string output_device_id_;
  84   const std::string input_device_id_;
  85
  86  private:
  87   DISALLOW_COPY_AND_ASSIGN(AudioOutputDispatcher);
  88 };
  89
  90 }  // namespace media
  91
  92 #endif  // MEDIA_AUDIO_AUDIO_OUTPUT_DISPATCHER_H_