Support reading pixels from HW-decoded video textures into canvas/webgl.

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"
@@ skipping 37 matching lines @@
       const gfx::Size& data_size,
       const gfx::Size& natural_size,
       base::TimeDelta timestamp);
 
   // Call prior to CreateFrame to ensure validity of frame configuration. Called
   // automatically by VideoDecoderConfig::IsValidConfig().
   // TODO(scherkus): VideoDecoderConfig shouldn't call this method
   static bool IsValidConfig(Format format, const gfx::Size& data_size,
                             const gfx::Size& natural_size);
 
+  // CB to write pixels from the texture backing this frame into the
+  // |void*| parameter.
+  typedef base::Callback<void(void*)> ReadPixelsCB;
+
   // Wraps a native texture of the given parameters with a VideoFrame.  When the
   // frame is destroyed |no_longer_needed.Run()| will be called.
   // |data_size| is the width and height of the frame data in pixels.
   // |natural_size| is the width and height of the frame when the frame's aspect
   // ratio is applied to |size|.
+  // |read_pixels_cb| may be used to do (slow!) readbacks from the
+  // texture to main memory.
   static scoped_refptr<VideoFrame> WrapNativeTexture(
       uint32 texture_id,
       uint32 texture_target,
       const gfx::Size& data_size,
       const gfx::Size& natural_size,
       base::TimeDelta timestamp,
+      const ReadPixelsCB& read_pixels_cb,
       const base::Closure& no_longer_needed);
 
+  // Read pixels from the native texture backing |*this| and write
+  // them to |*pixels| as RGBA.  |pixels| must point to a buffer at
+  // least as large as 4*data_size().width()*data_size().height().
+  void ReadPixelsFromNativeTexture(void* pixels);
+
   // Creates a frame with format equals to VideoFrame::EMPTY, width, height,
   // and timestamp are all 0.
   static scoped_refptr<VideoFrame> CreateEmptyFrame();
 
   // Allocates YV12 frame based on |width| and |height|, and sets its data to
   // the YUV equivalent of RGB(0,0,0).
   static scoped_refptr<VideoFrame> CreateBlackFrame(const gfx::Size& size);
 
   Format format() const { return format_; }
 
@@ skipping 64 matching lines @@
   // of the surface divided by the horizontal sampling period.  Note that
   // strides can be negative.
   int32 strides_[kMaxPlanes];
 
   // Array of data pointers to each plane.
   uint8* data_[kMaxPlanes];
 
   // Native texture ID, if this is a NATIVE_TEXTURE frame.
   uint32 texture_id_;
   uint32 texture_target_;
+  ReadPixelsCB read_pixels_cb_;
   base::Closure texture_no_longer_needed_;
 
   base::TimeDelta timestamp_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(VideoFrame);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_VIDEO_FRAME_H_