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 "media/audio/audio_device_thread.h"
  66 #include "media/audio/audio_output_ipc.h"
  67 #include "media/audio/audio_parameters.h"
  68 #include "media/audio/scoped_task_runner_observer.h"
  69 #include "media/base/audio_renderer_sink.h"
  70 #include "media/base/media_export.h"
  71
  72 namespace media {
  73
  74 class MEDIA_EXPORT AudioOutputDevice
  75     : NON_EXPORTED_BASE(public AudioRendererSink),
  76       NON_EXPORTED_BASE(public AudioOutputIPCDelegate),
  77       NON_EXPORTED_BASE(public ScopedTaskRunnerObserver) {
  78  public:
  79   // NOTE: Clients must call Initialize() before using.
  80   AudioOutputDevice(
  81       scoped_ptr<AudioOutputIPC> ipc,
  82       const scoped_refptr<base::SingleThreadTaskRunner>& io_task_runner);
  83
  84   // Initialize the stream using |session_id|, which is used for the browser
  85   // to select the correct input device.
  86   void InitializeWithSessionId(const AudioParameters& params,
  87                                RenderCallback* callback,
  88                                int session_id);
  89
  90   // AudioRendererSink implementation.
  91   void Initialize(const AudioParameters& params,
  92                   RenderCallback* callback) override;
  93   void Start() override;
  94   void Stop() override;
  95   void Play() override;
  96   void Pause() override;
  97   bool SetVolume(double volume) override;
  98
  99   // Methods called on IO thread ----------------------------------------------
 100   // AudioOutputIPCDelegate methods.
 101   void OnStateChanged(AudioOutputIPCDelegate::State state) override;
 102   void OnStreamCreated(base::SharedMemoryHandle handle,
 103                        base::SyncSocket::Handle socket_handle,
 104                        int length) override;
 105   void OnIPCClosed() override;
 106
 107  protected:
 108   // Magic required by ref_counted.h to avoid any code deleting the object
 109   // accidentally while there are references to it.
 110   friend class base::RefCountedThreadSafe<AudioOutputDevice>;
 111   ~AudioOutputDevice() override;
 112
 113  private:
 114   // Note: The ordering of members in this enum is critical to correct behavior!
 115   enum State {
 116     IPC_CLOSED,  // No more IPCs can take place.
 117     IDLE,  // Not started.
 118     CREATING_STREAM,  // Waiting for OnStreamCreated() to be called back.
 119     PAUSED,  // Paused.  OnStreamCreated() has been called.  Can Play()/Stop().
 120     PLAYING,  // Playing back.  Can Pause()/Stop().
 121   };
 122
 123   // Methods called on IO thread ----------------------------------------------
 124   // The following methods are tasks posted on the IO thread that need to
 125   // be executed on that thread.  They use AudioOutputIPC to send IPC messages
 126   // upon state changes.
 127   void CreateStreamOnIOThread(const AudioParameters& params);
 128   void PlayOnIOThread();
 129   void PauseOnIOThread();
 130   void ShutDownOnIOThread();
 131   void SetVolumeOnIOThread(double volume);
 132
 133   // base::MessageLoop::DestructionObserver implementation for the IO loop.
 134   // If the IO loop dies before we do, we shut down the audio thread from here.
 135   void WillDestroyCurrentMessageLoop() override;
 136
 137   AudioParameters audio_parameters_;
 138
 139   RenderCallback* callback_;
 140
 141   // A pointer to the IPC layer that takes care of sending requests over to
 142   // the AudioRendererHost.  Only valid when state_ != IPC_CLOSED and must only
 143   // be accessed on the IO thread.
 144   scoped_ptr<AudioOutputIPC> ipc_;
 145
 146   // Current state (must only be accessed from the IO thread).  See comments for
 147   // State enum above.
 148   State state_;
 149
 150   // State of Play() / Pause() calls before OnStreamCreated() is called.
 151   bool play_on_start_;
 152
 153   // The media session ID used to identify which input device to be started.
 154   // Only used by Unified IO.
 155   int session_id_;
 156
 157   // Our audio thread callback class.  See source file for details.
 158   class AudioThreadCallback;
 159
 160   // In order to avoid a race between OnStreamCreated and Stop(), we use this
 161   // guard to control stopping and starting the audio thread.
 162   base::Lock audio_thread_lock_;
 163   AudioDeviceThread audio_thread_;
 164   scoped_ptr<AudioOutputDevice::AudioThreadCallback> audio_callback_;
 165
 166   // Temporary hack to ignore OnStreamCreated() due to the user calling Stop()
 167   // so we don't start the audio thread pointing to a potentially freed
 168   // |callback_|.
 169   //
 170   // TODO(scherkus): Replace this by changing AudioRendererSink to either accept
 171   // the callback via Start(). See http://crbug.com/151051 for details.
 172   bool stopping_hack_;
 173
 174   DISALLOW_COPY_AND_ASSIGN(AudioOutputDevice);
 175 };
 176
 177 }  // namespace media
 178
 179 #endif  // MEDIA_AUDIO_AUDIO_OUTPUT_DEVICE_H_