media: Add support for playback of VP8 Alpha video streams

media/base/video_frame.h

 // 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.
 
 #ifndef MEDIA_BASE_VIDEO_FRAME_H_
 #define MEDIA_BASE_VIDEO_FRAME_H_
 
 #include "base/callback.h"
 #include "base/md5.h"
 #include "media/base/buffers.h"
 #include "ui/gfx/rect.h"
 #include "ui/gfx/size.h"
 
 namespace media {
 
 class MEDIA_EXPORT VideoFrame : public base::RefCountedThreadSafe<VideoFrame> {
  public:
   enum {
     kFrameSizeAlignment = 16,
     kFrameSizePadding = 16,
     kFrameAddressAlignment = 32
   };
 
   enum {
-    kMaxPlanes = 3,
+    kMaxPlanes = 4,
 
     kRGBPlane = 0,
 
     kYPlane = 0,
     kUPlane = 1,
     kVPlane = 2,
+    kAPlane = 3,
   };
 
   // Surface formats roughly based on FOURCC labels, see:
   // http://www.fourcc.org/rgb.php
   // http://www.fourcc.org/yuv.php
   // Keep in sync with WebKit::WebVideoFrame!
   enum Format {
     INVALID = 0,  // Invalid format value.  Used for error reporting.
     RGB32 = 4,  // 32bpp RGB packed with extra byte 8:8:8
     YV12 = 6,  // 12bpp YVU planar 1x1 Y, 2x2 VU samples
     YV16 = 7,  // 16bpp YVU planar 1x1 Y, 2x1 VU samples
     EMPTY = 9,  // An empty frame.
     I420 = 11,  // 12bpp YVU planar 1x1 Y, 2x2 UV samples.
     NATIVE_TEXTURE = 12,  // Native texture.  Pixel-format agnostic.
+    YV12A = 13,  // 20bpp YUVA planar 1x1 Y, 2x2 VU, 1x1 A samples.
   };
 
   // Creates a new frame in system memory with given parameters. Buffers for
   // the frame are allocated but not initialized.
   // |coded_size| is the width and height of the frame data in pixels.
   // |visible_rect| is the visible portion of |coded_size|, after cropping (if
   // any) is applied.
   // |natural_size| is the width and height of the frame when the frame's aspect
   // ratio is applied to |visible_rect|.
   static scoped_refptr<VideoFrame> CreateFrame(
@@ skipping 102 matching lines @@
     return timestamp_;
   }
   void SetTimestamp(const base::TimeDelta& timestamp) {
     timestamp_ = timestamp;
   }
 
   // Used to keep a running hash of seen frames.  Expects an initialized MD5
   // context.  Calls MD5Update with the context and the contents of the frame.
   void HashFrameForTesting(base::MD5Context* context);
 
+  bool HasAlpha() const {

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

this method is a bit deceiving

for example ... if format == NATIVE_TEXTURE, it would *seem* that this would be
an OK method to call when in reality it will hit a NOTREACHED().

where is this method used? I actually couldn't find a caller but I could have
skipped over it

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

sorry, this was a method  i used while debugging. it's not used anywhere now.
removing.

+    return IsValidPlane(kAPlane);
+  }
+
  private:
   friend class base::RefCountedThreadSafe<VideoFrame>;
   // Clients must use the static CreateFrame() method to create a new frame.
   VideoFrame(Format format,
              const gfx::Size& coded_size,
              const gfx::Rect& visible_rect,
              const gfx::Size& natural_size,
              base::TimeDelta timestamp);
   virtual ~VideoFrame();
 
@@ skipping 33 matching lines @@
   base::Closure no_longer_needed_cb_;
 
   base::TimeDelta timestamp_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(VideoFrame);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_VIDEO_FRAME_H_