Modifies size of ring buffer in shared memory on the audio capture side

media/audio/audio_input_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_input_device.h"
 
 #include "base/bind.h"
 #include "base/memory/scoped_vector.h"
 #include "base/threading/thread_restrictions.h"
 #include "base/time/time.h"
 #include "media/audio/audio_manager_base.h"
 #include "media/base/audio_bus.h"
 
 namespace media {
 
 // The number of shared memory buffer segments indicated to browser process
 // in order to avoid data overwriting. This number can be any positive number,
 // dependent how fast the renderer process can pick up captured data from
 // shared memory.
-static const int kRequestedSharedMemoryCount = 10;
+// TODO(henrika): figure out a suitable size of this ring buffer.
+// We have seen reports in Chrome where segments of repeated input audio has
+// damaged AEC performance in WebRTC clients. By setting its value to 1, we
+// reduce the number of places in Chrome where such a patteren could possibly
+// be created. The original value of kRequestedSharedMemoryCount was 10.
+// See b/13976602 for details.
+static const int kRequestedSharedMemoryCount = 1;
 
 // Takes care of invoking the capture callback on the audio thread.
 // An instance of this class is created for each capture stream in
 // OnLowLatencyCreated().
 class AudioInputDevice::AudioThreadCallback
     : public AudioDeviceThread::Callback {
  public:
   AudioThreadCallback(const AudioParameters& audio_parameters,
                       base::SharedMemoryHandle memory,
                       int memory_length,
@@ skipping 283 matching lines @@
   // and update the audio-delay measurement.
   int audio_delay_milliseconds = pending_data / bytes_per_ms_;
   capture_callback_->Capture(
       audio_bus, audio_delay_milliseconds, volume, key_pressed);
 
   if (++current_segment_id_ >= total_segments_)
     current_segment_id_ = 0;
 }
 
 }  // namespace media