Use passthrough decoder for (E)AC3 formats

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 a38e57a3770d17ad947a4fed7eada3b0b9349f9b..1e33f6bd2f9224d26bc105bae411e7b351ca8c43 100644
--- a/media/filters/android/media_codec_audio_decoder.cc
+++ b/media/filters/android/media_codec_audio_decoder.cc
@@ -4,11 +4,14 @@
 
 #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"
 #include "base/logging.h"
 #include "base/threading/thread_task_runner_handle.h"
+#include "media/base/ac3_util.h"
 #include "media/base/android/sdk_media_codec_bridge.h"
 #include "media/base/audio_buffer.h"
 #include "media/base/audio_timestamp_helper.h"
@@ -21,6 +24,8 @@ MediaCodecAudioDecoder::MediaCodecAudioDecoder(
     scoped_refptr<base::SingleThreadTaskRunner> task_runner)
     : task_runner_(task_runner),
       state_(STATE_UNINITIALIZED),
+      is_passthrough_(false),
+      sample_format_(kSampleFormatS16),
       channel_count_(0),
       channel_layout_(CHANNEL_LAYOUT_NONE),
       sample_rate_(0),
@@ -60,6 +65,19 @@ void MediaCodecAudioDecoder::Initialize(const AudioDecoderConfig& config,
   DCHECK_EQ(state_, STATE_UNINITIALIZED);
 
   InitCB bound_init_cb = BindToCurrentLoop(init_cb);
+  sample_format_ = kSampleFormatS16;
+  is_passthrough_ = false;
+
+  if (config.codec() == kCodecAC3) {
+    sample_format_ = kSampleFormatAc3;
+    is_passthrough_ = true;
+  } else if (config.codec() == kCodecEAC3) {
+    sample_format_ = kSampleFormatEac3;
+    is_passthrough_ = true;
+  }
+
+  // TODO(tsunghung): Add |is_passthrough_| in the following statement
+  // to enable passthrough decoder.
 
   // We can support only the codecs that AudioCodecBridge can decode.
   const bool is_codec_supported = config.codec() == kCodecVorbis ||
@@ -353,14 +371,42 @@ bool MediaCodecAudioDecoder::OnDecodedFrame(
   // of channels which can be different from |config_| value.
   DCHECK_GT(channel_count_, 0);
 
-  // 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 = 0;
+  scoped_refptr<AudioBuffer> audio_buffer;
+
+  if (is_passthrough_) {
+    const uint8_t* data = nullptr;
+    size_t data_size;
+    MediaCodecStatus status = media_codec->GetOutputBufferAddress(
+        out.index, out.offset, &data, &data_size);
+
+    if (status != MEDIA_CODEC_OK || !data) {
+      media_codec->ReleaseOutputBuffer(out.index, false);
+      return false;
+    }
+
+    if (config_.codec() == kCodecAC3) {
+      frame_count = Ac3Util::ParseTotalAc3SampleCount(data, data_size);
+    } else if (config_.codec() == kCodecEAC3) {
+      frame_count = Ac3Util::ParseTotalEac3SampleCount(data, data_size);
+    } else {
+      NOTREACHED() << "Unsupported passthrough format.";
+    }
 
-  // Create AudioOutput buffer based on current parameters.
-  scoped_refptr<AudioBuffer> audio_buffer =
-      AudioBuffer::CreateBuffer(kSampleFormatS16, channel_layout_,
-                                channel_count_, sample_rate_, frame_count);
+    // Create AudioOutput buffer based on current parameters.
+    audio_buffer = AudioBuffer::CreateBitstreamBuffer(
+        sample_format_, channel_layout_, channel_count_, sample_rate_,
+        frame_count, out.size);
+  } else {
+    // Android MediaCodec can only output 16bit PCM audio.
+    const int bytes_per_frame = sizeof(uint16_t) * channel_count_;
+    frame_count = out.size / bytes_per_frame;
+
+    // Create AudioOutput buffer based on current parameters.
+    audio_buffer =
+        AudioBuffer::CreateBuffer(sample_format_, channel_layout_,
+                                  channel_count_, sample_rate_, frame_count);
+  }
 
   // Copy data into AudioBuffer.
   CHECK_LE(out.size, audio_buffer->data_size());