media: Add support for playback of VP8 Alpha video streams

media/filters/ffmpeg_demuxer.cc

Index: media/filters/ffmpeg_demuxer.cc
diff --git a/media/filters/ffmpeg_demuxer.cc b/media/filters/ffmpeg_demuxer.cc
index 56929bcf05172823e0aab9b2ba7d8fe64e4c81b2..257d4aa8ea9094447646a2f2cdd6cb9c91065f3a 100644
--- a/media/filters/ffmpeg_demuxer.cc
+++ b/media/filters/ffmpeg_demuxer.cc
@@ -27,6 +27,10 @@
 #include "media/filters/ffmpeg_glue.h"
 #include "media/filters/ffmpeg_h264_to_annex_b_bitstream_converter.h"
 
+extern "C" {
+#include "third_party/ffmpeg/libavcodec/avcodec.h"

[scherkus (not reviewing), 2013/02/22 23:18:01]

this include should go inside ffmpeg_common.h

[vignesh, 2013/02/25 21:51:42]

Done.

+}
+
 namespace media {
 
 //
@@ -70,6 +74,11 @@ FFmpegDemuxerStream::FFmpegDemuxerStream(
 }
 
 void FFmpegDemuxerStream::EnqueuePacket(ScopedAVPacket packet) {
+

[scherkus (not reviewing), 2013/02/22 23:18:01]

remove extra blank line

[vignesh, 2013/02/25 21:51:42]

Done.

+  uint8_t* side_data;
+  int side_data_size = 0;
+  AVPacket* pkt;
+
   DCHECK(message_loop_->BelongsToCurrentThread());
 
   if (stopped_ || end_of_stream_) {
@@ -83,11 +92,21 @@ void FFmpegDemuxerStream::EnqueuePacket(ScopedAVPacket packet) {
     LOG(ERROR) << "Format conversion failed.";
   }
 
+  // Get the alpha data if any

[scherkus (not reviewing), 2013/02/22 23:18:01]

nit: I'm sure side data is used for more than just alpha -- I'd rephrase this to
talk about side data and include an example of VP8 alpha

[vignesh, 2013/02/25 21:51:42]

Done.

+  pkt = packet.get();
+  av_packet_split_side_data(pkt);
+  side_data = av_packet_get_side_data(pkt,
+                                      AV_PKT_DATA_MATROSKA_BLOCKADDITIONAL,
+                                      &side_data_size);
+
   // If a packet is returned by FFmpeg's av_parser_parse2() the packet will
   // reference inner memory of FFmpeg.  As such we should transfer the packet
   // into memory we control.
   scoped_refptr<DecoderBuffer> buffer;
-  buffer = DecoderBuffer::CopyFrom(packet->data, packet->size);
+  buffer = DecoderBuffer::CopyFrom(pkt->data, pkt->size);
+  if (side_data_size) {
+    buffer->SetSideData(side_data, side_data_size);
+  }
   buffer->SetTimestamp(ConvertStreamTimestamp(
       stream_->time_base, packet->pts));
   buffer->SetDuration(ConvertStreamTimestamp(