Use multiple shared memory buffers cyclically for audio capture.

content/common/media/audio_messages.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.
 
 // IPC messages for the audio.
 // Multiply-included message file, hence no include guard.
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 30 matching lines @@
 #else
 IPC_MESSAGE_CONTROL4(AudioMsg_NotifyStreamCreated,
                      int /* stream id */,
                      base::SharedMemoryHandle /* handle */,
                      base::FileDescriptor /* socket handle */,
                      uint32 /* length */)
 #endif
 
 // Tell the renderer process that an audio input stream has been created.
 // The renderer process would be given a SyncSocket that it should read
-// from from then on.
+// from from then on. It is also given total number of shared memory handles.
 #if defined(OS_WIN)
-IPC_MESSAGE_CONTROL4(AudioInputMsg_NotifyStreamCreated,
+IPC_MESSAGE_CONTROL3(AudioInputMsg_NotifyStreamCreated,
+                     int /* stream id */,
+                     base::SyncSocket::Handle /* socket handle */,
+                     uint32 /* total shared memory handles */)
+
+#else
+IPC_MESSAGE_CONTROL3(AudioInputMsg_NotifyStreamCreated,
+                     int /* stream id */,
+                     base::FileDescriptor /* socket handle */,
+                     uint32 /* total shared memory handles */)
+#endif
+
+// Tell the renderer process that a shared memory handle has been created.
+IPC_MESSAGE_CONTROL4(AudioInputMsg_NotifySharedMemoryCreated,
                      int /* stream id */,
                      base::SharedMemoryHandle /* handle */,
-                     base::SyncSocket::Handle /* socket handle */,
-                     uint32 /* length */)
-#else
-IPC_MESSAGE_CONTROL4(AudioInputMsg_NotifyStreamCreated,
-                     int /* stream id */,
-                     base::SharedMemoryHandle /* handle */,
-                     base::FileDescriptor /* socket handle */,
-                     uint32 /* length */)
-#endif
+                     uint32 /* length */,
+                     uint32 /* handle index */)
 
 // Notification message sent from AudioRendererHost to renderer after an output
 // device change has occurred.
 IPC_MESSAGE_CONTROL3(AudioMsg_NotifyDeviceChanged,
                      int /* stream_id */,
                      int /* new_buffer_size */,
                      int /* new_sample_rate */)
 
 // Notification message sent from AudioRendererHost to renderer for state
 // update after the renderer has requested a Create/Start/Close.
@@ skipping 15 matching lines @@
                      std::string /* device_id */)
 
 // Messages sent from the renderer to the browser.
 
 // Request that got sent to browser for creating an audio output stream
 IPC_MESSAGE_CONTROL2(AudioHostMsg_CreateStream,
                      int /* stream_id */,
                      media::AudioParameters /* params */)
 
 // Request that got sent to browser for creating an audio input stream
-IPC_MESSAGE_CONTROL4(AudioInputHostMsg_CreateStream,
+IPC_MESSAGE_CONTROL5(AudioInputHostMsg_CreateStream,
                      int /* stream_id */,
                      media::AudioParameters /* params */,
                      std::string /* device_id */,
-                     bool /* automatic_gain_control */)
+                     bool /* automatic_gain_control */,
+                     int /* shared memory count */)
 
 // Indicate that audio for a stream is produced by the specified render view.
 IPC_MESSAGE_CONTROL2(AudioHostMsg_AssociateStreamWithProducer,
                      int /* stream_id */,
                      int /* render_view_id */)
 
 // Indicate that audio for a stream is consumed by the specified render view.
 IPC_MESSAGE_CONTROL2(AudioInputHostMsg_AssociateStreamWithConsumer,
                      int /* stream_id */,
                      int /* render_view_id */)
@@ skipping 31 matching lines @@
 // Set audio volume of the input stream specified by stream_id.
 IPC_MESSAGE_CONTROL2(AudioInputHostMsg_SetVolume,
                      int /* stream_id */,
                      double /* volume */)
 
 // Start the device referenced by the session_id for the input stream specified
 // by stream_id.
 IPC_MESSAGE_CONTROL2(AudioInputHostMsg_StartDevice,
                      int /* stream_id */,
                      int /* session_id */)