media: Add support for playback of VP8 Alpha video streams

media/filters/ffmpeg_demuxer.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/ffmpeg_demuxer.h"
 
 #include <algorithm>
 #include <string>
 
 #include "base/bind.h"
@@ skipping 52 matching lines @@
   // Calculate the duration.
   duration_ = ConvertStreamTimestamp(stream->time_base, stream->duration);
 
   if (stream_->codec->codec_id == CODEC_ID_H264) {
     bitstream_converter_.reset(
         new FFmpegH264ToAnnexBBitstreamConverter(stream_->codec));
   }
 }
 
 void FFmpegDemuxerStream::EnqueuePacket(ScopedAVPacket packet) {
+  uint8* side_data;
+  int side_data_size = 0;
+  AVPacket* pkt;

[scherkus (not reviewing), 2013/02/27 07:28:26]

nit: this is C++! we can move these closer to where we use them ;)

(i.e., lines 93-95)

[vignesh, 2013/03/28 21:45:12]

yeah, i was writing this along side when i made the ffmpeg change. hence the C
mindset :)

+
   DCHECK(message_loop_->BelongsToCurrentThread());
 
   if (stopped_ || end_of_stream_) {
     NOTREACHED() << "Attempted to enqueue packet on a stopped stream";
     return;
   }
 
   // Convert the packet if there is a bitstream filter.
   if (packet->data && bitstream_converter_enabled_ &&
       !bitstream_converter_->ConvertPacket(packet.get())) {
     LOG(ERROR) << "Format conversion failed.";
   }
 
+  // Get side data if any. For now, the only type of side_data is VP8 Alpha. We
+  // keep this generic so that other side_data types in the future can be
+  // handled the same way as well.
+  pkt = packet.get();

[scherkus (not reviewing), 2013/02/27 07:28:26]

nit: can we inline the packet.get() calls instead of storing it as a local
variable?

[vignesh, 2013/03/28 21:45:12]

Done.

+  av_packet_split_side_data(pkt);
+  side_data = av_packet_get_side_data(pkt,
+                                      AV_PKT_DATA_MATROSKA_BLOCKADDITIONAL,

[scherkus (not reviewing), 2013/02/27 07:28:26]

is it safe to call this method with this enum for non-matroska formats? (e.g.,
mp3, mp4, avi, wav, ogg)

what happens when we do?

[vignesh, 2013/03/28 21:45:12]

we are requesting a very specific type of side data (which won't be present in
non-matroska formats of course). so, the method will return a NULL, setting
side_data_size to 0. So it is safe.

+                                      &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);
+  if (side_data_size > 0) {
+    buffer = DecoderBuffer::CopyFrom(pkt->data, pkt->size,
+                                     side_data, side_data_size);
+  } else {
+    buffer = DecoderBuffer::CopyFrom(pkt->data, pkt->size);
+  }
   buffer->SetTimestamp(ConvertStreamTimestamp(
       stream_->time_base, packet->pts));
   buffer->SetDuration(ConvertStreamTimestamp(
       stream_->time_base, packet->duration));
   if (buffer->GetTimestamp() != kNoTimestamp() &&
       last_packet_timestamp_ != kNoTimestamp() &&
       last_packet_timestamp_ < buffer->GetTimestamp()) {
     buffered_ranges_.Add(last_packet_timestamp_, buffer->GetTimestamp());
     demuxer_->NotifyBufferingChanged();
   }
@@ skipping 577 matching lines @@
   }
   for (size_t i = 0; i < buffered.size(); ++i)
     host_->AddBufferedTimeRange(buffered.start(i), buffered.end(i));
 }
 
 void FFmpegDemuxer::OnDataSourceError() {
   host_->OnDemuxerError(PIPELINE_ERROR_READ);
 }
 
 }  // namespace media