Support (E)AC3 passthrough

media/filters/android/media_codec_audio_decoder.cc

Index: media/filters/android/media_codec_audio_decoder.cc
diff --git a/media/filters/android/media_codec_audio_decoder.cc b/media/filters/android/media_codec_audio_decoder.cc
index c818d88cb751f21ab3c227913c55d9fa1bd87909..03192890458769673c354865c329cacf23002d22 100644
--- a/media/filters/android/media_codec_audio_decoder.cc
+++ b/media/filters/android/media_codec_audio_decoder.cc
@@ -4,6 +4,8 @@
 
 #include "media/filters/android/media_codec_audio_decoder.h"
 
+#include <cmath>
+
 #include "base/android/build_info.h"
 #include "base/bind.h"
 #include "base/callback_helpers.h"
@@ -21,6 +23,7 @@ MediaCodecAudioDecoder::MediaCodecAudioDecoder(
     scoped_refptr<base::SingleThreadTaskRunner> task_runner)
     : task_runner_(task_runner),
       state_(STATE_UNINITIALIZED),
+      is_passthrough_(false),
       channel_count_(0),
       channel_layout_(CHANNEL_LAYOUT_NONE),
       sample_rate_(0),
@@ -60,11 +63,12 @@ void MediaCodecAudioDecoder::Initialize(const AudioDecoderConfig& config,
   DCHECK_EQ(state_, STATE_UNINITIALIZED);
 
   InitCB bound_init_cb = BindToCurrentLoop(init_cb);
+  is_passthrough_ = (config.codec() == kCodecRaw);
 
   // We can support only the codecs that AudioCodecBridge can decode.
-  const bool is_codec_supported = config.codec() == kCodecVorbis ||
-                                  config.codec() == kCodecAAC ||
-                                  config.codec() == kCodecOpus;
+  const bool is_codec_supported =
+      config.codec() == kCodecVorbis || config.codec() == kCodecAAC ||
+      config.codec() == kCodecOpus || is_passthrough_;
   if (!is_codec_supported) {
     DVLOG(1) << "Unsuported codec " << GetCodecName(config.codec());
     bound_init_cb.Run(false);
@@ -297,6 +301,15 @@ void MediaCodecAudioDecoder::OnInputDataQueued(bool success) {
   if (input_queue_.front().first->end_of_stream() && success)
     return;
 
+  if (is_passthrough_ && success) {
+    scoped_refptr<DecoderBuffer> decoder_buffer = input_queue_.front().first;
+
+    if (!decoder_buffer->end_of_stream()) {
+      duration_queue_.push_back(std::make_pair(decoder_buffer->timestamp(),
+                                               decoder_buffer->duration()));
+    }
+  }
+
   input_queue_.front().second.Run(success ? DecodeStatus::OK
                                           : DecodeStatus::DECODE_ERROR);
   input_queue_.pop_front();
@@ -355,12 +368,35 @@ bool MediaCodecAudioDecoder::OnDecodedFrame(
 
   // Android MediaCodec can only output 16bit PCM audio.
   const int bytes_per_frame = sizeof(uint16_t) * channel_count_;
-  const size_t frame_count = out.size / bytes_per_frame;
+  size_t frame_count = out.size / bytes_per_frame;
+
+  if (is_passthrough_) {
+    // Retrieve duratioin information from PTS-duration pair queue.
+    base::TimeDelta duration;
+    while (!duration_queue_.empty()) {
+      PtsDurationPair pts_duration = duration_queue_.front();
+      duration_queue_.pop_front();
+
+      base::TimeDelta diff = pts_duration.first - out.pts;
+      if (diff.magnitude() < base::TimeDelta::FromMicroseconds(1)) {
+        duration = pts_duration.second;
+        break;
+      }
+    }
+
+    // Calculate the frame count of this compressed audio buffer.
+    frame_count =
+        std::round(config_.samples_per_second() * duration.InSecondsF());
+  }
+
+  const SampleFormat sample_format =
+      is_passthrough_ ? kSampleFormatRaw : kSampleFormatS16;
+  const size_t size = is_passthrough_ ? out.size : 0;
 
   // Create AudioOutput buffer based on current parameters.
   scoped_refptr<AudioBuffer> audio_buffer =
-      AudioBuffer::CreateBuffer(kSampleFormatS16, channel_layout_,
-                                channel_count_, sample_rate_, frame_count);
+      AudioBuffer::CreateBuffer(sample_format, channel_layout_, channel_count_,
+                                sample_rate_, frame_count, size);
 
   // Copy data into AudioBuffer.
   CHECK_LE(out.size, audio_buffer->data_size());