media/audio/audio_output_device.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 // Audio rendering unit utilizing audio output stream provided by browser
   6 // process through IPC.
   7 //
   8 // Relationship of classes.
   9 //
  10 //  AudioOutputController                AudioOutputDevice
  11 //           ^                                ^
  12 //           |                                |
  13 //           v               IPC              v
  14 //    AudioRendererHost  <---------> AudioOutputIPC (AudioMessageFilter)
  15 //
  16 // Transportation of audio samples from the render to the browser process
  17 // is done by using shared memory in combination with a sync socket pair
  18 // to generate a low latency transport. The AudioOutputDevice user registers an
  19 // AudioOutputDevice::RenderCallback at construction and will be polled by the
  20 // AudioOutputDevice for audio to be played out by the underlying audio layers.
  21 //
  22 // State sequences.
  23 //
  24 //            Task [IO thread]                  IPC [IO thread]
  25 //
  26 // Start -> CreateStreamOnIOThread -----> CreateStream ------>
  27 //       <- OnStreamCreated <- AudioMsg_NotifyStreamCreated <-
  28 //       ---> PlayOnIOThread -----------> PlayStream -------->
  29 //
  30 // Optionally Play() / Pause() sequences may occur:
  31 // Play -> PlayOnIOThread --------------> PlayStream --------->
  32 // Pause -> PauseOnIOThread ------------> PauseStream -------->
  33 // (note that Play() / Pause() sequences before OnStreamCreated are
  34 //  deferred until OnStreamCreated, with the last valid state being used)
  35 //
  36 // AudioOutputDevice::Render => audio transport on audio thread =>
  37 //                               |
  38 // Stop --> ShutDownOnIOThread -------->  CloseStream -> Close
  39 //
  40 // This class utilizes several threads during its lifetime, namely:
  41 // 1. Creating thread.
  42 //    Must be the main render thread.
  43 // 2. Control thread (may be the main render thread or another thread).
  44 //    The methods: Start(), Stop(), Play(), Pause(), SetVolume()
  45 //    must be called on the same thread.
  46 // 3. IO thread (internal implementation detail - not exposed to public API)
  47 //    The thread within which this class receives all the IPC messages and
  48 //    IPC communications can only happen in this thread.
  49 // 4. Audio transport thread (See AudioDeviceThread).
  50 //    Responsible for calling the AudioThreadCallback implementation that in
  51 //    turn calls AudioRendererSink::RenderCallback which feeds audio samples to
  52 //    the audio layer in the browser process using sync sockets and shared
  53 //    memory.
  54 //
  55 // Implementation notes:
  56 // - The user must call Stop() before deleting the class instance.
  57
  58 #ifndef MEDIA_AUDIO_AUDIO_OUTPUT_DEVICE_H_
  59 #define MEDIA_AUDIO_AUDIO_OUTPUT_DEVICE_H_
  60
  61 #include "base/basictypes.h"
  62 #include "base/bind.h"
  63 #include "base/memory/scoped_ptr.h"
  64 #include "base/memory/shared_memory.h"
  65 #include "base/message_loop/message_loop.h"
  66 #include "media/audio/audio_device_thread.h"
  67 #include "media/audio/audio_output_ipc.h"
  68 #include "media/audio/audio_parameters.h"
  69 #include "media/audio/scoped_loop_observer.h"
  70 #include "media/base/audio_renderer_sink.h"
  71 #include "media/base/media_export.h"
  72
  73 namespace media {
  74
  75 class MEDIA_EXPORT AudioOutputDevice
  76     : NON_EXPORTED_BASE(public AudioRendererSink),
  77       NON_EXPORTED_BASE(public AudioOutputIPCDelegate),
  78       NON_EXPORTED_BASE(public ScopedLoopObserver) {
  79  public:
  80   // NOTE: Clients must call Initialize() before using.
  81   AudioOutputDevice(scoped_ptr<AudioOutputIPC> ipc,
  82                     const scoped_refptr<base::MessageLoopProxy>& io_loop);
  83
  84   // Initialize function for clients wishing to have unified input and
  85   // output, |params| may specify |input_channels| > 0, representing a
  86   // number of input channels which will be at the same sample-rate
  87   // and buffer-size as the output as specified in |params|. |session_id| is
  88   // used for the browser to select the correct input device.
  89   // In this case, the callback's RenderIO() method will be called instead
  90   // of Render(), providing the synchronized input data at the same time as
  91   // when new output data is to be rendered.
  92   void InitializeUnifiedStream(const AudioParameters& params,
  93                                RenderCallback* callback,
  94                                int session_id);
  95
  96   // AudioRendererSink implementation.
  97   virtual void Initialize(const AudioParameters& params,
  98                           RenderCallback* callback) OVERRIDE;
  99   virtual void Start() OVERRIDE;
 100   virtual void Stop() OVERRIDE;
 101   virtual void Play() OVERRIDE;
 102   virtual void Pause() OVERRIDE;
 103   virtual bool SetVolume(double volume) OVERRIDE;
 104
 105   // Methods called on IO thread ----------------------------------------------
 106   // AudioOutputIPCDelegate methods.
 107   virtual void OnStateChanged(AudioOutputIPCDelegate::State state) OVERRIDE;
 108   virtual void OnStreamCreated(base::SharedMemoryHandle handle,
 109                                base::SyncSocket::Handle socket_handle,
 110                                int length) OVERRIDE;
 111   virtual void OnIPCClosed() OVERRIDE;
 112
 113  protected:
 114   // Magic required by ref_counted.h to avoid any code deleting the object
 115   // accidentally while there are references to it.
 116   friend class base::RefCountedThreadSafe<AudioOutputDevice>;
 117   virtual ~AudioOutputDevice();
 118
 119  private:
 120   // Note: The ordering of members in this enum is critical to correct behavior!
 121   enum State {
 122     IPC_CLOSED,  // No more IPCs can take place.
 123     IDLE,  // Not started.
 124     CREATING_STREAM,  // Waiting for OnStreamCreated() to be called back.
 125     PAUSED,  // Paused.  OnStreamCreated() has been called.  Can Play()/Stop().
 126     PLAYING,  // Playing back.  Can Pause()/Stop().
 127   };
 128
 129   // Methods called on IO thread ----------------------------------------------
 130   // The following methods are tasks posted on the IO thread that need to
 131   // be executed on that thread.  They use AudioOutputIPC to send IPC messages
 132   // upon state changes.
 133   void CreateStreamOnIOThread(const AudioParameters& params);
 134   void PlayOnIOThread();
 135   void PauseOnIOThread();
 136   void ShutDownOnIOThread();
 137   void SetVolumeOnIOThread(double volume);
 138
 139   // base::MessageLoop::DestructionObserver implementation for the IO loop.
 140   // If the IO loop dies before we do, we shut down the audio thread from here.
 141   virtual void WillDestroyCurrentMessageLoop() OVERRIDE;
 142
 143   AudioParameters audio_parameters_;
 144
 145   RenderCallback* callback_;
 146
 147   // A pointer to the IPC layer that takes care of sending requests over to
 148   // the AudioRendererHost.  Only valid when state_ != IPC_CLOSED and must only
 149   // be accessed on the IO thread.
 150   scoped_ptr<AudioOutputIPC> ipc_;
 151
 152   // Current state (must only be accessed from the IO thread).  See comments for
 153   // State enum above.
 154   State state_;
 155
 156   // State of Play() / Pause() calls before OnStreamCreated() is called.
 157   bool play_on_start_;
 158
 159   // The media session ID used to identify which input device to be started.
 160   // Only used by Unified IO.
 161   int session_id_;
 162
 163   // Our audio thread callback class.  See source file for details.
 164   class AudioThreadCallback;
 165
 166   // In order to avoid a race between OnStreamCreated and Stop(), we use this
 167   // guard to control stopping and starting the audio thread.
 168   base::Lock audio_thread_lock_;
 169   AudioDeviceThread audio_thread_;
 170   scoped_ptr<AudioOutputDevice::AudioThreadCallback> audio_callback_;
 171
 172   // Temporary hack to ignore OnStreamCreated() due to the user calling Stop()
 173   // so we don't start the audio thread pointing to a potentially freed
 174   // |callback_|.
 175   //
 176   // TODO(scherkus): Replace this by changing AudioRendererSink to either accept
 177   // the callback via Start(). See http://crbug.com/151051 for details.
 178   bool stopping_hack_;
 179
 180   DISALLOW_COPY_AND_ASSIGN(AudioOutputDevice);
 181 };
 182
 183 }  // namespace media
 184
 185 #endif  // MEDIA_AUDIO_AUDIO_OUTPUT_DEVICE_H_