Pass more detailed audio hardware configuration information to the renderer

media/audio/mac/audio_manager_mac.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/mac/audio_manager_mac.h"
 
 #include <CoreAudio/AudioHardware.h>
 #include <string>
 
 #include "base/bind.h"
@@ skipping 318 matching lines @@
   AudioDeviceID audio_device_id = GetAudioDeviceIdByUId(true, device_id);
   AudioInputStream* stream = NULL;
   if (audio_device_id != kAudioObjectUnknown)
     stream = new AUAudioInputStream(this, params, audio_device_id);
 
   return stream;
 }
 
 AudioParameters AudioManagerMac::GetPreferredOutputStreamParameters(
     const AudioParameters& input_params) {
-  ChannelLayout channel_layout = CHANNEL_LAYOUT_STEREO;
+  ChannelLayout channel_layout = CHANNEL_LAYOUT_UNSUPPORTED;
+  
   int input_channels = 0;
   if (input_params.IsValid()) {
     channel_layout = input_params.channel_layout();

[DaleCurtis, 2013/03/06 19:19:30]

Instead of doing this I think you should use FFmpegCommon::GuessChannelLayout()
(please move this function into the channel_layout.{cc,h} file when
CHANNEL_LAYOUT is NOT channel_layout_discrete. This will fix
http://crbug.com/169396 

[Chris Rogers, 2013/03/07 00:34:17]

I think I've changed it to be more in line with your thinking here.

     input_channels = input_params.input_channels();
 
     if (CommandLine::ForCurrentProcess()->HasSwitch(
         switches::kEnableWebAudioInput)) {
       // TODO(crogers): given the limitations of the AudioOutputStream
       // back-ends used with kEnableWebAudioInput, we hard-code to stereo.
       // Specifically, this is a limitation of AudioSynchronizedStream which
       // can be removed as part of the work to consolidate these back-ends.
       channel_layout = CHANNEL_LAYOUT_STEREO;
     }
   }
 
-  return AudioParameters(
-      AudioParameters::AUDIO_PCM_LOW_LATENCY, channel_layout, input_channels,
-      AUAudioOutputStream::HardwareSampleRate(), 16,
+  AudioParameters params(
+      AudioParameters::AUDIO_PCM_LOW_LATENCY,
+      channel_layout,
+      input_channels,
+      AUAudioOutputStream::HardwareSampleRate(),
+      16,
       kDefaultLowLatencyBufferSize);
+
+  if (channel_layout == CHANNEL_LAYOUT_UNSUPPORTED) {
+    int channels = 2;
+    int channels_per_frame;
+    AudioHardwareUnifiedStream::GetDefaultOutputChannels(
+      &channels, &channels_per_frame);

[DaleCurtis, 2013/03/06 19:19:30]

4 space indent.

[Chris Rogers, 2013/03/07 00:34:17]

Done.

+
+    params.SetDiscreteChannels(channels);
+  }
+  
+  return params;
 }
 
 void AudioManagerMac::CreateDeviceListener() {
   DCHECK(GetMessageLoop()->BelongsToCurrentThread());
   output_device_listener_.reset(new AudioDeviceListenerMac(base::Bind(
       &AudioManagerMac::DelayedDeviceChange, base::Unretained(this))));
 }
 
 void AudioManagerMac::DestroyDeviceListener() {
   DCHECK(GetMessageLoop()->BelongsToCurrentThread());
   output_device_listener_.reset();
 }
 
 void AudioManagerMac::DelayedDeviceChange() {
   // TODO(dalecurtis): This is ridiculous, but we need to delay device changes
   // to workaround threading issues with OSX property listener callbacks.  See
   // http://crbug.com/158170
   GetMessageLoop()->PostDelayedTask(FROM_HERE, base::Bind(
       &AudioManagerMac::NotifyAllOutputDeviceChangeListeners,
       base::Unretained(this)), base::TimeDelta::FromSeconds(2));
 }
 
 AudioManager* CreateAudioManager() {
   return new AudioManagerMac();
 }
 
 }  // namespace media