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 SingleThreadTaskRunner;
  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& device_id);
  42
  43   // Called by AudioOutputProxy to open the stream.
  44   // Returns false, if it fails to open it.
  45   virtual bool OpenStream() = 0;
  46
  47   // Called by AudioOutputProxy when the stream is started.
  48   // Uses |callback| to get source data and report errors, if any.
  49   // Does *not* take ownership of this callback.
  50   // Returns true if started successfully, false otherwise.
  51   virtual bool StartStream(AudioOutputStream::AudioSourceCallback* callback,
  52                            AudioOutputProxy* stream_proxy) = 0;
  53
  54   // Called by AudioOutputProxy when the stream is stopped.
  55   // Ownership of the |stream_proxy| is passed to the dispatcher.
  56   virtual void StopStream(AudioOutputProxy* stream_proxy) = 0;
  57
  58   // Called by AudioOutputProxy when the volume is set.
  59   virtual void StreamVolumeSet(AudioOutputProxy* stream_proxy,
  60                                double volume) = 0;
  61
  62   // Called by AudioOutputProxy when the stream is closed.
  63   virtual void CloseStream(AudioOutputProxy* stream_proxy) = 0;
  64
  65   // Called on the audio thread when the AudioManager is shutting down.
  66   virtual void Shutdown() = 0;
  67
  68   const std::string& device_id() const { return device_id_; }
  69
  70  protected:
  71   friend class base::RefCountedThreadSafe<AudioOutputDispatcher>;
  72   virtual ~AudioOutputDispatcher();
  73
  74   // A no-reference-held pointer (we don't want circular references) back to the
  75   // AudioManager that owns this object.
  76   AudioManager* audio_manager_;
  77   const scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
  78   const AudioParameters params_;
  79   std::string device_id_;
  80
  81  private:
  82   DISALLOW_COPY_AND_ASSIGN(AudioOutputDispatcher);
  83 };
  84
  85 }  // namespace media
  86
  87 #endif  // MEDIA_AUDIO_AUDIO_OUTPUT_DISPATCHER_H_