Support Opus Ambisonics playback

content/renderer/media/audio_renderer_mixer_manager.cc

Index: content/renderer/media/audio_renderer_mixer_manager.cc
diff --git a/content/renderer/media/audio_renderer_mixer_manager.cc b/content/renderer/media/audio_renderer_mixer_manager.cc
index f22bdc3f6d7c94d38cff3ee3f6ac4e05466c47ac..03b5fe86820095cda9a96fcbf29f813243d0fa49 100644
--- a/content/renderer/media/audio_renderer_mixer_manager.cc
+++ b/content/renderer/media/audio_renderer_mixer_manager.cc
@@ -70,10 +70,17 @@ media::AudioParameters GetMixerOutputParams(
 
   DCHECK_NE(output_buffer_size, 0);
 
+  // If the input has discrete channel layout, the hardware channel mapping is

[DaleCurtis, 2017/03/29 22:46:55]

Is this necessary here? I would have thought the browser side would handle it
appropriately.

[flim-chromium, 2017/03/30 19:35:10]

Without this check, I get the browser failing with an "Aw, Snap!" page crash.
Should this be handled somewhere else instead?

[DaleCurtis, 2017/03/30 20:22:21]

What's crashing?

[flim-chromium, 2017/03/31 00:12:14]

The stack trace is:

[1:12:0330/163613.993344:FATAL:audio_converter.cc(35)] Check failed:
input_params.IsValid(). 
#0 0x7f6c917eca6b base::debug::StackTrace::StackTrace()
#1 0x7f6c917eb76c base::debug::StackTrace::StackTrace()
#2 0x7f6c9185496f logging::LogMessage::~LogMessage()
#3 0x7f6c88445ff0 media::AudioConverter::AudioConverter()
#4 0x7f6c8844ecf2 media::AudioRendererMixer::AudioRendererMixer()
#5 0x7f6c8c0a5485 content::AudioRendererMixerManager::GetMixer()
#6 0x7f6c88454507 media::AudioRendererMixerInput::Start()
#7 0x7f6c7ca40e1f media::WebAudioSourceProviderImpl::Start()
#8 0x7f6c8832cd15 media::AudioRendererImpl::OnAudioBufferStreamInitialized()
...

where input_params in audio_converter.cc(35) has DISCRETE layout but 0 channels.

[DaleCurtis, 2017/03/31 19:06:53]

Seem like AudioConverter needs to be taught how to handle discrete channels.

[flim-chromium, 2017/04/05 18:19:34]

As discussed offline, I've removed this and added a webaudio check in
AudioRendererImpl instead.

+  // unknown. Default to the hardware channel layout instead. Any input
+  // channels beyond the hardware channel count will not be played out.
+  media::ChannelLayout channel_layout =
+      input_params.channel_layout() == media::CHANNEL_LAYOUT_DISCRETE
+          ? hardware_params.channel_layout()
+          : input_params.channel_layout();
+
   // Force to 16-bit output for now since we know that works everywhere;
   // ChromeOS does not support other bit depths.
-  media::AudioParameters params(input_params.format(),
-                                input_params.channel_layout(),
+  media::AudioParameters params(input_params.format(), channel_layout,
                                 output_sample_rate, 16, output_buffer_size);
 
   // Specify the latency info to be passed to the browser side.