media: Add support for playback of VP8 Alpha video streams

media/ffmpeg/ffmpeg_common.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/ffmpeg/ffmpeg_common.h"
 
 #include "base/basictypes.h"
 #include "base/logging.h"
 #include "media/base/decoder_buffer.h"
 #include "media/base/video_frame.h"
@@ skipping 364 matching lines @@
     // TODO(tomfinegan): libavcodec doesn't know about VP9.
     format = VideoFrame::YV12;
     coded_size = natural_size;
   }
 
   bool is_encrypted = false;
   AVDictionaryEntry* key = av_dict_get(stream->metadata, "enc_key_id", NULL, 0);
   if (key)
     is_encrypted = true;
 
+  AVDictionaryEntry* webm_alpha =
+      av_dict_get(stream->metadata, "alpha_mode", NULL, 0);
+  if (webm_alpha && !strcmp(webm_alpha->value, "1")) {
+    format = VideoFrame::YV12A;
+  }
+
   config->Initialize(codec,
                      profile,
                      format,
                      coded_size, visible_rect, natural_size,
                      stream->codec->extradata, stream->codec->extradata_size,
                      is_encrypted,
                      true);
 }
 
 void VideoDecoderConfigToAVCodecContext(
@@ skipping 88 matching lines @@
 VideoFrame::Format PixelFormatToVideoFormat(PixelFormat pixel_format) {
   switch (pixel_format) {
     case PIX_FMT_YUV422P:
       return VideoFrame::YV16;
     // TODO(scherkus): We should be paying attention to the color range of each
     // format and scaling as appropriate when rendering. Regular YUV has a range
     // of 16-239 where as YUVJ has a range of 0-255.
     case PIX_FMT_YUV420P:
     case PIX_FMT_YUVJ420P:
       return VideoFrame::YV12;
+    case PIX_FMT_YUVA420P:
+      return VideoFrame::YV12A;
     default:
       DVLOG(1) << "Unsupported PixelFormat: " << pixel_format;
   }
   return VideoFrame::INVALID;
 }
 
 PixelFormat VideoFormatToPixelFormat(VideoFrame::Format video_format) {
   switch (video_format) {
     case VideoFrame::YV16:
       return PIX_FMT_YUV422P;
     case VideoFrame::YV12:
       return PIX_FMT_YUV420P;
+    case VideoFrame::YV12A:
+      return PIX_FMT_YUVA420P;
     default:
       DVLOG(1) << "Unsupported VideoFrame::Format: " << video_format;
   }
   return PIX_FMT_NONE;
 }
 
 }  // namespace media