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 476 matching lines @@
   base::TimeDelta delay =
       base::TimeDelta::FromMicroseconds(buffer->params.delay);
 
   base::TimeTicks delay_timestamp =
       base::TimeTicks() +
       base::TimeDelta::FromMicroseconds(buffer->params.delay_timestamp);
 
   DVLOG(4) << __func__ << " delay:" << delay << " delay_timestamp:" << delay
            << " frames_skipped:" << frames_skipped;
 
+  output_bus_->set_is_bitstream_format(audio_parameters_.IsBitstreamFormat());

[DaleCurtis, 2017/06/15 21:46:31]

if (audio_parameters_.IsBitstreamFormat()) {
  output_bus_->set_is_bitstream_format(true);
  output_bus_->set_data_size(0);
  output_bus_->set_frames(audio_parameters_.frames_per_buffer());
}

[AndyWu, 2017/08/02 01:43:39]

Done.

+  if (audio_parameters_.IsBitstreamFormat()) {
+    // 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(delay, delay_timestamp, frames_skipped,
                            output_bus_.get());
+  buffer->params.frames = output_bus_->frames();

[DaleCurtis, 2017/06/15 21:46:31]

Hmm, this is always audio_parameters_.frames_per_buffer() ? Is that a mistake?
Otherwise there's no point in sending this information over.

[AndyWu, 2017/08/02 01:43:39]

To make things clear, I changed to GetBitstreamFrames(). It should be PCM frame
count of a compressed audio frame.

+  buffer->params.data_size = output_bus_->data_size();
 }
 
 bool AudioOutputDevice::AudioThreadCallback::
     CurrentThreadIsAudioDeviceThread() {
   return thread_checker_.CalledOnValidThread();
 }
 
 }  // namespace media