audio_device_thread.h revision 1e9bf3e0803691d0a228da41fc608347b6db4340 
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#ifndef MEDIA_AUDIO_AUDIO_DEVICE_THREAD_H_
6#define MEDIA_AUDIO_AUDIO_DEVICE_THREAD_H_
7
8#include "base/basictypes.h"
9#include "base/memory/ref_counted.h"
10#include "base/memory/scoped_ptr.h"
11#include "base/memory/shared_memory.h"
12#include "base/sync_socket.h"
13#include "base/synchronization/lock.h"
14#include "media/audio/audio_parameters.h"
15#include "media/base/media_export.h"
16
17namespace base {
18class MessageLoop;
19}
20
21namespace media {
22class AudioBus;
23
24// Data transfer between browser and render process uses a combination
25// of sync sockets and shared memory. To read from the socket and render
26// data, we use a worker thread, a.k.a. the AudioDeviceThread, which reads
27// data from the browser via the socket and fills the shared memory from the
28// audio thread via the AudioDeviceThread::Callback interface/class.
29// For more details see the documentation in audio_device.h.
30//
31// TODO(tommi): Multiple audio input/output device instances should be able to
32// share the same thread instead of spinning one per instance.
33class MEDIA_EXPORT AudioDeviceThread {
34 public:
35  // This is the callback interface/base class that Audio[Output|Input]Device
36  // implements to render input/output data. The callbacks run on the
37  // thread owned by AudioDeviceThread.
38  class Callback {
39   public:
40    Callback(const AudioParameters& audio_parameters,
41             base::SharedMemoryHandle memory,
42             int memory_length,
43             int total_segments);
44    virtual ~Callback();
45
46    // One time initialization for the callback object on the audio thread.
47    void InitializeOnAudioThread();
48
49    // Derived implementations must call shared_memory_.Map appropriately
50    // before Process can be called.
51    virtual void MapSharedMemory() = 0;
52
53    // Called whenever we receive notifications about pending data.
54    virtual void Process(int pending_data) = 0;
55
56   protected:
57    // Protected so that derived classes can access directly.
58    // The variables are 'const' since values are calculated/set in the
59    // constructor and must never change.
60    const AudioParameters audio_parameters_;
61    const int samples_per_ms_;
62    const int bytes_per_ms_;
63
64    base::SharedMemory shared_memory_;
65    const int memory_length_;
66    const int total_segments_;
67    int segment_length_;
68
69   private:
70    DISALLOW_COPY_AND_ASSIGN(Callback);
71  };
72
73  AudioDeviceThread();
74  ~AudioDeviceThread();
75
76  // Starts the audio thread. The thread must not already be running.  If
77  // |sychronized_buffers| is set, the browser expects to be notified via the
78  // |socket| every time AudioDeviceThread::Process() completes.
79  void Start(AudioDeviceThread::Callback* callback,
80             base::SyncSocket::Handle socket,
81             const char* thread_name,
82             bool synchronized_buffers);
83
84  // This tells the audio thread to stop and clean up the data.
85  // The method can stop the thread synchronously or asynchronously.
86  // In the latter case, the thread will still be running after Stop()
87  // returns, but the callback pointer is cleared so no further callbacks will
88  // be made (IOW after Stop() returns, it is safe to delete the callback).
89  // The |loop_for_join| parameter is required for asynchronous operation
90  // in order to join the worker thread and close the thread handle later via a
91  // posted task.
92  // If set to NULL, function will wait for the thread to exit before returning.
93  void Stop(base::MessageLoop* loop_for_join);
94
95  // Returns true if the thread is stopped or stopping.
96  bool IsStopped();
97
98 private:
99  // Our own private SimpleThread override.  We implement this in a
100  // private class so that we get the following benefits:
101  // 1) AudioDeviceThread doesn't expose SimpleThread methods.
102  //    I.e. the caller can't call Start()/Stop() - which would be bad.
103  // 2) We override ThreadMain to add additional on-thread initialization
104  //    while still synchronized with SimpleThread::Start() to provide
105  //    reliable initialization.
106  class Thread;
107
108  base::Lock thread_lock_;
109  scoped_refptr<AudioDeviceThread::Thread> thread_;
110
111  DISALLOW_COPY_AND_ASSIGN(AudioDeviceThread);
112};
113
114}  // namespace media.
115
116#endif  // MEDIA_AUDIO_AUDIO_DEVICE_THREAD_H_
117