Implementation of 'AudioContext.getOutputTimestamp' method

media/audio/audio_device_thread.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MEDIA_AUDIO_AUDIO_DEVICE_THREAD_H_
 #define MEDIA_AUDIO_AUDIO_DEVICE_THREAD_H_
 
 #include <stdint.h>
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/shared_memory.h"
 #include "base/sync_socket.h"
 #include "base/synchronization/lock.h"
+#include "media/audio/audio_io.h"
 #include "media/base/audio_parameters.h"
 #include "media/base/media_export.h"
 
 namespace base {
 class MessageLoop;
 }
 
 namespace media {
 class AudioBus;
+struct AudioTimestamp;
 
 // Data transfer between browser and render process uses a combination
 // of sync sockets and shared memory. To read from the socket and render
 // data, we use a worker thread, a.k.a. the AudioDeviceThread, which reads
 // data from the browser via the socket and fills the shared memory from the
 // audio thread via the AudioDeviceThread::Callback interface/class.
 // For more details see the documentation in audio_device.h.
 //
 // TODO(tommi): Multiple audio input/output device instances should be able to
 // share the same thread instead of spinning one per instance.
@@ skipping 11 matching lines @@
     virtual ~Callback();
 
     // One time initialization for the callback object on the audio thread.
     void InitializeOnAudioThread();
 
     // Derived implementations must call shared_memory_.Map appropriately
     // before Process can be called.
     virtual void MapSharedMemory() = 0;
 
     // Called whenever we receive notifications about pending input data.
-    virtual void Process(uint32_t pending_data) = 0;
+    // It also provides the current audio stream timestamp on the device.
+    virtual void Process(uint32_t pending_data,
+                         const AudioTimestamp& timestamp) = 0;
 
    protected:
     // Protected so that derived classes can access directly.
     // The variables are 'const' since values are calculated/set in the
     // constructor and must never change.
     const AudioParameters audio_parameters_;
     const double samples_per_ms_;
     const double bytes_per_ms_;
     const uint32_t bytes_per_frame_;
 
     base::SharedMemory shared_memory_;
     const int memory_length_;
     const int total_segments_;
     int segment_length_;
 
    private:
     DISALLOW_COPY_AND_ASSIGN(Callback);
   };
 
   AudioDeviceThread();
   ~AudioDeviceThread();
 
+  // Represents a data packet to be received via the socket.
+  struct Packet {
+    uint32_t pending_data;
+    AudioTimestamp timestamp;
+  };
+
   // Starts the audio thread. The thread must not already be running.  If
   // |sychronized_buffers| is set, the browser expects to be notified via the
   // |socket| every time AudioDeviceThread::Process() completes.
   void Start(AudioDeviceThread::Callback* callback,
              base::SyncSocket::Handle socket,
              const char* thread_name,
              bool synchronized_buffers);
 
   // This tells the audio thread to stop and clean up the data.
   // The method can stop the thread synchronously or asynchronously.
@@ skipping 21 matching lines @@
 
   base::Lock thread_lock_;
   scoped_refptr<AudioDeviceThread::Thread> thread_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioDeviceThread);
 };
 
 }  // namespace media.
 
 #endif  // MEDIA_AUDIO_AUDIO_DEVICE_THREAD_H_