media: Add support for playback of VP8 Alpha video streams

webkit/media/filter_helpers.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 "webkit/media/filter_helpers.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "media/base/filter_collection.h"
 #include "media/base/media_switches.h"
@@ skipping 18 matching lines @@
   }
 }
 
 // Constructs and adds the default video decoders to |filter_collection|.
 //
 // Note that decoders in the |filter_collection| are initialized in order.
 static void AddDefaultDecodersToCollection(
     const scoped_refptr<base::MessageLoopProxy>& message_loop,
     media::FilterCollection* filter_collection) {
 
-  scoped_refptr<media::FFmpegVideoDecoder> ffmpeg_video_decoder =
-      new media::FFmpegVideoDecoder(message_loop);
-  filter_collection->GetVideoDecoders()->push_back(ffmpeg_video_decoder);
-
   // TODO(phajdan.jr): Remove ifdefs when libvpx with vp9 support is released
   // (http://crbug.com/174287) .
 #if !defined(MEDIA_DISABLE_LIBVPX)
   const CommandLine* cmd_line = CommandLine::ForCurrentProcess();
-  if (cmd_line->HasSwitch(switches::kEnableVp9Playback)) {
+  if (cmd_line->HasSwitch(switches::kEnableVp9Playback) ||
+      cmd_line->HasSwitch(switches::kEnableVp8AlphaPlayback) ) {
     scoped_refptr<media::VpxVideoDecoder> vpx_video_decoder =
         new media::VpxVideoDecoder(message_loop);
     filter_collection->GetVideoDecoders()->push_back(vpx_video_decoder);
   }
 #endif  // !defined(MEDIA_DISABLE_LIBVPX)
+
+  scoped_refptr<media::FFmpegVideoDecoder> ffmpeg_video_decoder =
+      new media::FFmpegVideoDecoder(message_loop);
+  filter_collection->GetVideoDecoders()->push_back(ffmpeg_video_decoder);

[scherkus (not reviewing), 2013/04/10 00:22:24]

FYI this means that we'll no longer use FFmpeg's VP8 decoder when one of those
two flags are enabled.

Not something you need to worry about for now ... but one day :)

[vignesh, 2013/04/10 17:59:16]

That's not really true, there are checks in vpx_video_decoder.cc (lines 115-126)
to make sure that it handles the right format of videos when the right flags are
passed. For instance, a VP8 video without alpha will always use FFmpeg's VP8
decoder.

 }
 
 void BuildMediaSourceCollection(
     const scoped_refptr<media::ChunkDemuxer>& demuxer,
     const scoped_refptr<base::MessageLoopProxy>& message_loop,
     media::FilterCollection* filter_collection) {
   DCHECK(demuxer);
   filter_collection->SetDemuxer(demuxer);
 
   // Remove GPUVideoDecoder until it supports codec config changes.
   // TODO(acolwell): Remove this once http://crbug.com/151045 is fixed.
   DCHECK_LE(filter_collection->GetVideoDecoders()->size(), 1u);
   filter_collection->GetVideoDecoders()->clear();
 
   AddDefaultDecodersToCollection(message_loop, filter_collection);
 }
 
 void BuildDefaultCollection(
     const scoped_refptr<media::DataSource>& data_source,
     const scoped_refptr<base::MessageLoopProxy>& message_loop,
     media::FilterCollection* filter_collection,
     const media::FFmpegNeedKeyCB& need_key_cb) {
   filter_collection->SetDemuxer(new media::FFmpegDemuxer(
       message_loop, data_source, need_key_cb));
 
   AddDefaultDecodersToCollection(message_loop, filter_collection);
 }
 
 }  // webkit_media