Allow audio system to handle synchronized low-latency audio I/O

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/message_loop.h"
 #include "base/threading/thread_restrictions.h"
 #include "base/time.h"
@@ skipping 288 matching lines @@
   LOG(ERROR) << "IO loop going away before the input device has been stopped";
   ShutDownOnIOThread();
 }
 
 // AudioInputDevice::AudioThreadCallback
 AudioInputDevice::AudioThreadCallback::AudioThreadCallback(
     const AudioParameters& audio_parameters,
     base::SharedMemoryHandle memory,
     int memory_length,
     CaptureCallback* capture_callback)
-    : AudioDeviceThread::Callback(audio_parameters, memory, memory_length),
+    : AudioDeviceThread::Callback(audio_parameters, 0, memory, memory_length),

[tommi (sloooow) - chröme, 2012/09/07 09:58:19]

It is a bit odd that the AudioInputDevice class passes 0 for the number of input
devices.  I know the reason for it but we're making an architectural change that
makes things confusing.  Will AudioInputDevice eventually be going away?

[Chris Rogers, 2012/09/07 20:34:01]

When I first created the AudioDevice class, I had anticipated that it could be
used for both input and/or output.  I think we have a great opportunity to
rework some of this code, and potentially remove AudioInputDevice.  Obviously we
need to look carefully here and discuss this.  But I'm optimistic that we can
actually simplify this all in the end, given some careful work.

       capture_callback_(capture_callback) {
   audio_bus_ = AudioBus::Create(audio_parameters_);
 }
 
 AudioInputDevice::AudioThreadCallback::~AudioThreadCallback() {
 }
 
 void AudioInputDevice::AudioThreadCallback::MapSharedMemory() {
   shared_memory_.Map(memory_length_);
 }
@@ skipping 16 matching lines @@
   // with nominal range -1.0 -> +1.0.
   audio_bus_->FromInterleaved(memory, audio_bus_->frames(), bytes_per_sample);
 
   // Deliver captured data to the client in floating point format
   // and update the audio-delay measurement.
   capture_callback_->Capture(audio_bus_.get(),
                              audio_delay_milliseconds, volume);
 }
 
 }  // namespace media