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>
 #include <utility>
 
 #include "base/callback_helpers.h"
 #include "base/macros.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/threading/thread_restrictions.h"
 #include "base/time/time.h"
 #include "base/timer/timer.h"
 #include "base/trace_event/trace_event.h"
 #include "build/build_config.h"
 #include "media/audio/audio_device_description.h"
 #include "media/audio/audio_output_controller.h"
 #include "media/base/limits.h"
 
 namespace media {
 
+static const int kMaxFramesPerCompressedAudioBuffer = 4096;

[DaleCurtis, 2016/11/01 23:05:13]

This needs to be a property of the AudioParameters class; that said where did
you get this number from?

[AndyWu, 2016/11/04 18:04:24]

Done, thanks for your help.

+
 // Takes care of invoking the render callback on the audio thread.
 // An instance of this class is created for each capture stream in
 // OnStreamCreated().
 class AudioOutputDevice::AudioThreadCallback
     : public AudioDeviceThread::Callback {
  public:
   AudioThreadCallback(const AudioParameters& audio_parameters,
                       base::SharedMemoryHandle memory,
                       int memory_length,
                       AudioRendererSink::RenderCallback* render_callback);
@@ skipping 432 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());
+  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(kMaxFramesPerCompressedAudioBuffer);
+  }
   // 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