audio_output_device.h revision 5821806d5e7f356e8fa4b058a389a808ea183019 
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/message_loop.h"
65#include "base/shared_memory.h"
66#include "media/base/media_export.h"
67#include "media/audio/audio_device_thread.h"
68#include "media/audio/audio_output_ipc.h"
69#include "media/audio/audio_parameters.h"
70#include "media/audio/scoped_loop_observer.h"
71#include "media/base/audio_renderer_sink.h"
72
73namespace media {
74
75class MEDIA_EXPORT AudioOutputDevice
76    : NON_EXPORTED_BASE(public AudioRendererSink),
77      public AudioOutputIPCDelegate,
78      NON_EXPORTED_BASE(public ScopedLoopObserver) {
79 public:
80  // AudioRendererSink implementation.
81  virtual void Initialize(const AudioParameters& params,
82                          RenderCallback* callback) OVERRIDE;
83  virtual void InitializeIO(const AudioParameters& params,
84                            int input_channels,
85                            RenderCallback* callback) OVERRIDE;
86  virtual void Start() OVERRIDE;
87  virtual void Stop() OVERRIDE;
88  virtual void Play() OVERRIDE;
89  virtual void Pause(bool flush) OVERRIDE;
90  virtual bool SetVolume(double volume) OVERRIDE;
91
92  // Methods called on IO thread ----------------------------------------------
93  // AudioOutputIPCDelegate methods.
94  virtual void OnStateChanged(AudioOutputIPCDelegate::State state) OVERRIDE;
95  virtual void OnStreamCreated(base::SharedMemoryHandle handle,
96                               base::SyncSocket::Handle socket_handle,
97                               int length) OVERRIDE;
98  virtual void OnIPCClosed() OVERRIDE;
99
100  // Creates an uninitialized AudioOutputDevice. Clients must call Initialize()
101  // before using.
102  // TODO(tommi): When all dependencies on |content| have been removed
103  // from AudioOutputDevice, move this class over to media/audio.
104  AudioOutputDevice(AudioOutputIPC* ipc,
105                    const scoped_refptr<base::MessageLoopProxy>& io_loop);
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  // Methods called on IO thread ----------------------------------------------
115  // The following methods are tasks posted on the IO thread that needs to
116  // be executed on that thread. They interact with AudioMessageFilter and
117  // sends IPC messages on that thread.
118  void CreateStreamOnIOThread(const AudioParameters& params,
119                              int input_channels);
120  void PlayOnIOThread();
121  void PauseOnIOThread(bool flush);
122  void ShutDownOnIOThread();
123  void SetVolumeOnIOThread(double volume);
124
125  // MessageLoop::DestructionObserver implementation for the IO loop.
126  // If the IO loop dies before we do, we shut down the audio thread from here.
127  virtual void WillDestroyCurrentMessageLoop() OVERRIDE;
128
129  AudioParameters audio_parameters_;
130
131  // The number of optional synchronized input channels having the same
132  // sample-rate and buffer-size as specified in audio_parameters_.
133  int input_channels_;
134
135  RenderCallback* callback_;
136
137  // A pointer to the IPC layer that takes care of sending requests over to
138  // the AudioRendererHost.
139  AudioOutputIPC* ipc_;
140
141  // Our stream ID on the message filter. Only accessed on the IO thread.
142  // Must only be modified on the IO thread.
143  int stream_id_;
144
145  // State of Play() / Pause() calls before OnStreamCreated() is called.
146  bool play_on_start_;
147
148  // Set to |true| when OnStreamCreated() is called.
149  // Set to |false| when ShutDownOnIOThread() is called.
150  // This is for use with play_on_start_ to track Play() / Pause() state.
151  // Must only be touched from the IO thread.
152  bool is_started_;
153
154  // Our audio thread callback class.  See source file for details.
155  class AudioThreadCallback;
156
157  // In order to avoid a race between OnStreamCreated and Stop(), we use this
158  // guard to control stopping and starting the audio thread.
159  base::Lock audio_thread_lock_;
160  AudioDeviceThread audio_thread_;
161  scoped_ptr<AudioOutputDevice::AudioThreadCallback> audio_callback_;
162
163  // Temporary hack to ignore OnStreamCreated() due to the user calling Stop()
164  // so we don't start the audio thread pointing to a potentially freed
165  // |callback_|.
166  //
167  // TODO(scherkus): Replace this by changing AudioRendererSink to either accept
168  // the callback via Start(). See http://crbug.com/151051 for details.
169  bool stopping_hack_;
170
171  DISALLOW_COPY_AND_ASSIGN(AudioOutputDevice);
172};
173
174}  // namespace media
175
176#endif  // MEDIA_AUDIO_AUDIO_OUTPUT_DEVICE_H_
177