Downstream Communication with the Video Renderer

When connected to the Overlay Mixer, the Microsoft® DirectShow® Video Renderer filter does not actually render the video at all. The connection is an IOverlay connection rather than an IMemInputPin connection. This enables the Overlay Mixer to do the actual rendering, so that the Video Renderer is responsible only for creating the window and controlling its size and location on the desktop. This window can be a top-level window, or a child window within an application. The Overlay Mixer and Video Renderer hold a continual conversation during graph operation by means of IOverlay on the video renderer and IOverlayNotify on the Overlay Mixer. In addition to window size and position information, the Video Renderer passes its window handle through the Overlay Mixer to DirectDraw, which manages the rectangle clipping. Applications can control the Video Renderer through its IVideoWindow and IBasicVideo2 interfaces.