This is the VideoCaptureDevice implementation for windows.

media/video/capture/win/sink_filter_observer_win.h

Index: media/video/capture/win/sink_filter_observer_win.h
===================================================================
--- media/video/capture/win/sink_filter_observer_win.h	(revision 0)
+++ media/video/capture/win/sink_filter_observer_win.h	(revision 0)
@@ -0,0 +1,24 @@
+// Copyright (c) 2011 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.
+
+// Observer class of Sinkfilter. The implementor of this class receive video
+// frames from the SinkFilter DirectShow filter.
+
+#ifndef MEDIA_VIDEO_CAPTURE_WIN_SINK_FILTER_OBSERVER_WIN_H_
+#define MEDIA_VIDEO_CAPTURE_WIN_SINK_FILTER_OBSERVER_WIN_H_
+
+namespace media {
+
+class SinkFilterObserver {
+ public:
+  // SinkFilter will call this function with all frames delivered to it.
+  // buffer in only valid during this function call.
+  virtual void FrameReceived(const uint8* buffer, int length) = 0;
+ protected:
+  virtual ~SinkFilterObserver();
+};
+
+}  // namespace media
+
+#endif  // MEDIA_VIDEO_CAPTURE_WIN_SINK_FILTER_OBSERVER_WIN_H_