Support Opus Ambisonics playback

media/renderers/audio_renderer_impl.cc

Index: media/renderers/audio_renderer_impl.cc
diff --git a/media/renderers/audio_renderer_impl.cc b/media/renderers/audio_renderer_impl.cc
index 7cb22ffb1695abb831acbfac99a6b19983c33dae..8fbb8416c6d9917f685001a48a09c56afc2af969 100644
--- a/media/renderers/audio_renderer_impl.cc
+++ b/media/renderers/audio_renderer_impl.cc
@@ -49,6 +49,7 @@ AudioRendererImpl::AudioRendererImpl(
       last_audio_memory_usage_(0),
       last_decoded_sample_rate_(0),
       last_decoded_channel_layout_(CHANNEL_LAYOUT_NONE),
+      last_decoded_channels_(0),
       playback_rate_(0.0),
       state_(kUninitialized),
       buffering_state_(BUFFERING_HAVE_NOTHING),
@@ -361,6 +362,8 @@ void AudioRendererImpl::Initialize(DemuxerStream* stream,
                             stream->audio_decoder_config().samples_per_second(),
                             stream->audio_decoder_config().bits_per_channel(),
                             buffer_size);
+    audio_parameters_.set_channels_for_discrete(
+        stream->audio_decoder_config().channels());
     buffer_converter_.reset();
   } else {
     // To allow for seamless sample rate adaptations (i.e. changes from say
@@ -378,8 +381,7 @@ void AudioRendererImpl::Initialize(DemuxerStream* stream,
     }
 #endif
 
-    int stream_channel_count = ChannelLayoutToChannelCount(
-        stream->audio_decoder_config().channel_layout());
+    int stream_channel_count = stream->audio_decoder_config().channels();
 
     bool try_supported_channel_layouts = false;
 #if defined(OS_WIN)
@@ -419,20 +421,24 @@ void AudioRendererImpl::Initialize(DemuxerStream* stream,
     //   renderer. Browser-side will down-mix to the hardware config. If the
     //   hardware later changes to equal stream channels, browser-side will stop
     //   down-mixing and use the data from all stream channels.
+    bool use_hw_config = hw_channel_count > stream_channel_count;
     ChannelLayout renderer_channel_layout =
-        hw_channel_count > stream_channel_count
-            ? hw_channel_layout
-            : stream->audio_decoder_config().channel_layout();
+        use_hw_config ? hw_channel_layout
+                      : stream->audio_decoder_config().channel_layout();
 
     audio_parameters_.Reset(hw_params.format(), renderer_channel_layout,
                             sample_rate, hw_params.bits_per_sample(),
                             media::AudioLatency::GetHighLatencyBufferSize(
                                 sample_rate, preferred_buffer_size));
+    if (!use_hw_config)
+      audio_parameters_.set_channels_for_discrete(stream_channel_count);
   }
 
   last_decoded_channel_layout_ =
       stream->audio_decoder_config().channel_layout();
 
+  last_decoded_channels_ = stream->audio_decoder_config().channels();
+
   audio_clock_.reset(
       new AudioClock(base::TimeDelta(), audio_parameters_.sample_rate()));
 
@@ -580,6 +586,7 @@ void AudioRendererImpl::DecodedAudioReady(
 
       if (last_decoded_channel_layout_ != buffer->channel_layout()) {
         last_decoded_channel_layout_ = buffer->channel_layout();
+        last_decoded_channels_ = buffer->channel_count();
 
         // Input layouts should never be discrete.
         DCHECK_NE(last_decoded_channel_layout_, CHANNEL_LAYOUT_DISCRETE);
@@ -965,14 +972,10 @@ void AudioRendererImpl::ConfigureChannelMask() {
   DCHECK(audio_parameters_.IsValid());
   DCHECK_NE(last_decoded_channel_layout_, CHANNEL_LAYOUT_NONE);
   DCHECK_NE(last_decoded_channel_layout_, CHANNEL_LAYOUT_UNSUPPORTED);
-  DCHECK_NE(last_decoded_channel_layout_, CHANNEL_LAYOUT_DISCRETE);
-
-  const int input_channel_count =
-      ChannelLayoutToChannelCount(last_decoded_channel_layout_);
 
   // If we're actually downmixing the signal, no mask is necessary, but ensure
   // we clear any existing mask if present.
-  if (input_channel_count >= audio_parameters_.channels()) {
+  if (last_decoded_channels_ >= audio_parameters_.channels()) {
     algorithm_->SetChannelMask(
         std::vector<bool>(audio_parameters_.channels(), true));
     return;
@@ -980,7 +983,7 @@ void AudioRendererImpl::ConfigureChannelMask() {
 
   // Determine the matrix used to upmix the channels.
   std::vector<std::vector<float>> matrix;
-  ChannelMixingMatrix(last_decoded_channel_layout_, input_channel_count,
+  ChannelMixingMatrix(last_decoded_channel_layout_, last_decoded_channels_,
                       audio_parameters_.channel_layout(),
                       audio_parameters_.channels())
       .CreateTransformationMatrix(&matrix);