Support (E)AC3 passthrough

media/audio/audio_output_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_output_device.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <cmath>
@@ skipping 458 matching lines @@
   // Read and reset the number of frames skipped.
   AudioOutputBuffer* buffer =
       reinterpret_cast<AudioOutputBuffer*>(shared_memory_.memory());
   uint32_t frames_skipped = buffer->params.frames_skipped;
   buffer->params.frames_skipped = 0;
 
   DVLOG(4) << __func__ << " pending_data:" << pending_data
            << " frames_delayed(pre-round):" << frames_delayed
            << " frames_skipped:" << frames_skipped;
 
+  output_bus_->set_is_raw_format(audio_parameters_.IsRawFormat());

[DaleCurtis, 2016/11/04 21:24:53]

What happens if you output zeros when in bitstreaming mode? Is that still
silence? If so I think it makes sense to not modify AudioBus and just always
send even multiples of 4 bytes in frames. Padding the last buffer with zeros.

[chcunningham, 2017/06/14 20:03:08]

Also curious about the meaning of zeroes.

+  if (audio_parameters_.IsRawFormat()) {
+    // Reset the data size and frame count.
+    // For compressed audio formats, the data size and frame count will be
+    // updated by |render_callback_|.
+    output_bus_->set_data_size(0);
+    output_bus_->set_frames(audio_parameters_.frames_per_buffer());
+    ;
+  }
   // Update the audio-delay measurement, inform about the number of skipped
   // frames, and ask client to render audio.  Since |output_bus_| is wrapping
   // the shared memory the Render() call is writing directly into the shared
   // memory.
   render_callback_->Render(output_bus_.get(), std::round(frames_delayed),
                            frames_skipped);
+  buffer->params.frames = output_bus_->frames();
+  buffer->params.data_size = output_bus_->data_size();
 }
 
 bool AudioOutputDevice::AudioThreadCallback::
     CurrentThreadIsAudioDeviceThread() {
   return thread_checker_.CalledOnValidThread();
 }
 
 }  // namespace media