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 virtual void Initialize(const AudioParameters& params, 92 RenderCallback* callback) OVERRIDE; 93 virtual void Start() OVERRIDE; 94 virtual void Stop() OVERRIDE; 95 virtual void Play() OVERRIDE; 96 virtual void Pause() OVERRIDE; 97 virtual bool SetVolume(double volume) OVERRIDE; 98 99 // Methods called on IO thread ---------------------------------------------- 100 // AudioOutputIPCDelegate methods. 101 virtual void OnStateChanged(AudioOutputIPCDelegate::State state) OVERRIDE; 102 virtual void OnStreamCreated(base::SharedMemoryHandle handle, 103 base::SyncSocket::Handle socket_handle, 104 int length) OVERRIDE; 105 virtual 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 virtual ~AudioOutputDevice(); 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 virtual 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_ 180
