DirectDraw Exclusive Mode

The Overlay Mixer's DirectDraw exclusive mode enables games to display video on some part of the screen. In this mode, the Overlay Mixer renders the video directly to a DirectDraw surface created by the game application, rather than to a window provided by the Video Renderer. This enables games to control the color key. The Overlay Mixer exposes only one input pin in DirectDraw exclusive mode, which means that no mixing of Line 21 or DVD subpicture can be performed in this mode.

To use the Overlay Mixer in DirectDraw exclusive mode, create an instance of the Overlay Mixer and obtain its IDDrawExclModeVideo interface before building the filter graph, and add the DirectDraw surfaces to the Overlay Mixer. The Overlay Mixer will ensure that the rendering is done into the DirectDraw surface. One significant limitation of this mode is that the game does not get access to the actual video bits. If you use IDDrawExclModeVideo, your application creates the primary surface, and the Overlay Mixer creates the overlay surface.

You can also use DirectDraw exclusive mode to perform windowless rendering—for example, in a Web page—but this is not recommended, because the Overlay Mixer does not perform any mixing in this mode. This means that no line 21 or subpicture data can be displayed. To write a DVD playback application in windowless mode, the recommended approach is to use the MSWebDVD ActiveX® control.