Support (E)AC3 passthrough

media/base/audio_bus.h

 // 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.
 
 #ifndef MEDIA_BASE_AUDIO_BUS_H_
 #define MEDIA_BASE_AUDIO_BUS_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 54 matching lines @@
   // Uses channels() and frames_per_buffer() from AudioParameters if given.
   static int CalculateMemorySize(int channels, int frames);
   static int CalculateMemorySize(const AudioParameters& params);
 
   // Methods that are expected to be called after AudioBus::CreateWrapper() in
   // order to wrap externally allocated memory. Note: It is illegal to call
   // these methods when using a factory method other than CreateWrapper().
   void SetChannelData(int channel, float* data);
   void set_frames(int frames);
 
+  int data_size() const { return data_size_; }
+  void set_data_size(int data_size);

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

hacker_style() methods must be inline; I know we have some on here that aren't,
but don't add more. But that said, why are these changes necessary? Last we
discussed the RAW formats are all CBR, so you should be able to just construct a
single channel AudioBus with frames/4 size (1 byte vs float). Then you shouldn't
need to modify this class at all.

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

Thanks, I fixed hacker_style() methods.

Last time you pointed out that both AC3 and EAC3 are CBR. However, there are
more RAW formats:
https://developer.android.com/reference/android/media/AudioFormat.html
DTS-HD MA is VBR:
http://www.audiogurus.com/learn/electronics/dts-hd-master-audio/186
Do we really want to support CBR only?

One question, how to get "audio bit rate" in AudioRendererImpl::Initialize()?
That would be the key if we want to support CBR only and keep changes minimum.

+
+  int is_raw_format() const { return is_raw_format_; }
+  void set_is_raw_format(bool is_raw_format);
+
   // Overwrites the sample values stored in this AudioBus instance with values
   // from a given interleaved |source_buffer| with expected layout
   // [ch0, ch1, ..., chN, ch0, ch1, ...] and sample values in the format
   // corresponding to the given SourceSampleTypeTraits.
   // The sample values are converted to float values by means of the method
   // convert_to_float32() provided by the SourceSampleTypeTraits. For a list of
   // ready-to-use SampleTypeTraits, see file audio_sample_types.h.
   // If |num_frames_to_write| is less than frames(), the remaining frames are
   // zeroed out. If |num_frames_to_write| is more than frames(), this results in
   // undefined behavior.
@@ skipping 117 matching lines @@
 
   template <class TargetSampleTypeTraits>
   static void CopyConvertFromAudioBusToInterleavedTarget(
       const AudioBus* source,
       int read_offset_in_frames,
       int num_frames_to_read,
       typename TargetSampleTypeTraits::ValueType* dest_buffer);
 
   // Contiguous block of channel memory.
   std::unique_ptr<float, base::AlignedFreeDeleter> data_;
+  int data_size_;
+  bool is_raw_format_;
 
   // One float pointer per channel pointing to a contiguous block of memory for
   // that channel. If the memory is owned by this instance, this will
   // point to the memory in |data_|. Otherwise, it may point to memory provided
   // by the client.
   std::vector<float*> channel_data_;
   int frames_;
 
   // Protect SetChannelData() and set_frames() for use by CreateWrapper().
   bool can_set_channel_data_;
@@ skipping 98 matching lines @@
 
   AudioBusRefCounted(int channels, int frames);
   ~AudioBusRefCounted() override;
 
   DISALLOW_COPY_AND_ASSIGN(AudioBusRefCounted);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_AUDIO_BUS_H_