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