Overlay Mixer

The Overlay Mixer filter acts as a video renderer filter that takes advantage of DirectDraw hardware capabilities to provide higher quality video playback. It guarantees the use of a destination color-keyed DirectDraw hardware overlay surface for video input to its first (or primary) input pin. The Overlay Mixer filter also supports other enhancements and features, including:

Mixing video input to the secondary pins by the input into the color key on the DirectDraw primary surface.
Using video port video sources when connecting a WDM Stream Class driver to the Overlay Mixer's primary pin via the proxy filter.
Playing video while in DirectDraw Exclusive mode.
Using interlaced video types and non-square pixel aspect ratios by supporting media types with VIDEOINFOHEADER2
Supporting out-of-order IMemAllocator::GetBuffer and IMemInputPin::Receive calls for out-of-order decoders such as MPEG.