Support (E)AC3 passthrough

media/filters/audio_renderer_algorithm.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/filters/audio_renderer_algorithm.h"
 
 #include <algorithm>
 #include <cmath>
 
 #include "base/logging.h"
@@ skipping 59 matching lines @@
 // is blocked for a significant amount of time, decoding can stall. By
 // maintaining a larger audio buffer we are more resilient to underflows
 // caused by long running main thread tasks.
 // TODO(watk,xhwang): Delete this when decrypting moves to the media thread
 // (http://crbug.com/403462).
 static const int kStartingCapacityForEncryptedInMs = 500;
 
 AudioRendererAlgorithm::AudioRendererAlgorithm()
     : channels_(0),
       samples_per_second_(0),
+      is_bitstream_format_(false),
       muted_partial_frame_(0),
       capacity_(0),
       output_time_(0.0),
       search_block_center_offset_(0),
       search_block_index_(0),
       num_candidate_blocks_(0),
       target_block_index_(0),
       ola_window_size_(0),
       ola_hop_size_(0),
       num_complete_frames_(0),
       initial_capacity_(0),
       max_capacity_(0) {}
 
 AudioRendererAlgorithm::~AudioRendererAlgorithm() {}
 
 void AudioRendererAlgorithm::Initialize(const AudioParameters& params,
                                         bool is_encrypted) {
   CHECK(params.IsValid());
 
   channels_ = params.channels();
   samples_per_second_ = params.sample_rate();
+  is_bitstream_format_ = params.IsBitstreamFormat();
   initial_capacity_ = capacity_ = std::max(
       params.frames_per_buffer() * 2,
       ConvertMillisecondsToFrames(is_encrypted
                                       ? kStartingCapacityForEncryptedInMs
                                       : kStartingCapacityInMs));
   max_capacity_ =
       std::max(initial_capacity_, kMaxCapacityInSeconds * samples_per_second_);
   num_candidate_blocks_ = ConvertMillisecondsToFrames(kWsolaSearchIntervalMs);
   ola_window_size_ = ConvertMillisecondsToFrames(kOlaWindowSizeMs);
 
@@ skipping 39 matching lines @@
 int AudioRendererAlgorithm::FillBuffer(AudioBus* dest,
                                        int dest_offset,
                                        int requested_frames,
                                        double playback_rate) {
   if (playback_rate == 0)
     return 0;
 
   DCHECK_GT(playback_rate, 0);
   DCHECK_EQ(channels_, dest->channels());
 
+  dest->set_is_bitstream_format(is_bitstream_format_);

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

this block too could use some documentation for future readers about why we skip
logic below.

[AndyWu, 2017/08/02 01:43:41]

Done.

+  if (is_bitstream_format_) {
+    dest->set_data_size(0);

[DaleCurtis, 2017/06/15 21:46:32]

Why?

[AndyWu, 2017/08/02 01:43:40]

Removed.

+    dest->set_frames(0);
+
+    return audio_buffer_.ReadFrames(requested_frames, dest_offset, dest);
+  }
+
   // Optimize the muted case to issue a single clear instead of performing
   // the full crossfade and clearing each crossfaded frame.
   if (playback_rate < kMinPlaybackRate || playback_rate > kMaxPlaybackRate) {
     int frames_to_render =
         std::min(static_cast<int>(audio_buffer_.frames() / playback_rate),
                  requested_frames);
 
     // Compute accurate number of frames to actually skip in the source data.
     // Includes the leftover partial frame from last request. However, we can
     // only skip over complete frames, so a partial frame may remain for next
@@ skipping 278 matching lines @@
     }
   }
 
   target_block_wrapper_ =
       AudioBus::WrapVector(target_block_->frames(), active_target_channels);
   search_block_wrapper_ =
       AudioBus::WrapVector(search_block_->frames(), active_search_channels);
 }
 
 }  // namespace media