Use multiple shared memory buffers cyclically for audio capture.

media/audio/audio_output_device.cc

 // 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.
 
 #include "media/audio/audio_output_device.h"
 
 #include "base/debug/trace_event.h"
 #include "base/message_loop.h"
 #include "base/threading/thread_restrictions.h"
 #include "base/time.h"
@@ skipping 239 matching lines @@
 
 // AudioOutputDevice::AudioThreadCallback
 
 AudioOutputDevice::AudioThreadCallback::AudioThreadCallback(
     const AudioParameters& audio_parameters,
     base::SharedMemoryHandle memory,
     int memory_length,
     AudioRendererSink::RenderCallback* render_callback)
     : AudioDeviceThread::Callback(audio_parameters,
                                   memory,
-                                  memory_length),
+                                  memory_length,
+                                  1),
       render_callback_(render_callback) {
 }
 
 AudioOutputDevice::AudioThreadCallback::~AudioThreadCallback() {
 }
 
 void AudioOutputDevice::AudioThreadCallback::MapSharedMemory() {
+  CHECK_EQ(1, total_segments_);

[DaleCurtis, 2013/03/07 02:04:37]

TMYK: http://what-if.xkcd.com/3/

   CHECK(shared_memory_.Map(TotalSharedMemorySizeInBytes(memory_length_)));
 
   // Calculate output and input memory size.
   int output_memory_size = AudioBus::CalculateMemorySize(audio_parameters_);
   int input_channels = audio_parameters_.input_channels();
   int frames = audio_parameters_.frames_per_buffer();
   int input_memory_size =
       AudioBus::CalculateMemorySize(input_channels, frames);
 
   int io_size = output_memory_size + input_memory_size;
@@ skipping 45 matching lines @@
   // TODO(dalecurtis): Technically this is not always correct.  Due to channel
   // padding for alignment, there may be more data available than this.  We're
   // relying on AudioSyncReader::Read() to parse this with that in mind.  Rename
   // these methods to Set/GetActualFrameCount().
   SetActualDataSizeInBytes(
       &shared_memory_, memory_length_,
       num_frames * sizeof(*output_bus_->channel(0)) * output_bus_->channels());
 }
 
 }  // namespace media.