Always use the source channel layout with AudioBufferConverter.

media/filters/audio_renderer_impl.cc

Index: media/filters/audio_renderer_impl.cc
diff --git a/media/filters/audio_renderer_impl.cc b/media/filters/audio_renderer_impl.cc
index 0dff76f37d7f3a222a30befb0bb057ee54f66d6c..16e3b44d1c03c50797381b5f237fc4d03ef4f9c1 100644
--- a/media/filters/audio_renderer_impl.cc
+++ b/media/filters/audio_renderer_impl.cc
@@ -283,13 +283,18 @@ void AudioRendererImpl::Initialize(DemuxerStream* stream,
   } else {
     // TODO(rileya): Support hardware config changes
     const AudioParameters& hw_params = hardware_config_->GetOutputConfig();
-    audio_parameters_.Reset(hw_params.format(),
-                            hw_params.channel_layout(),
-                            hw_params.channels(),
-                            hw_params.input_channels(),
-                            hw_params.sample_rate(),
-                            hw_params.bits_per_sample(),
-                            hardware_config_->GetHighLatencyBufferSize());
+    audio_parameters_.Reset(
+        hw_params.format(),
+        // To avoid unnecessary upmixing and platform specific issues around
+        // channel layouts (http://crbug.com/266674) only allow channel down

[wolenetz, 2014/05/30 23:01:00]

nit: Upmixing is still allowed, but to no higher than the channels initialized
here (which are no longer the full hw support, but whatever the first init
segment had). Adjust comment?

[DaleCurtis, 2014/05/30 23:08:57]

Done.

+        // mixing within the AudioBufferConverter.
+        stream->audio_decoder_config().channel_layout(),
+        ChannelLayoutToChannelCount(
+            stream->audio_decoder_config().channel_layout()),
+        hw_params.input_channels(),
+        hw_params.sample_rate(),
+        hw_params.bits_per_sample(),
+        hardware_config_->GetHighLatencyBufferSize());
   }
 
   audio_clock_.reset(new AudioClock(audio_parameters_.sample_rate()));