Building the DVD Filter Graph

The recommended way to build the DVD playback filter graph is to have a DVD Graph Builder object do it for you automatically. This approach is demonstrated below and in the DVD sample application. If you need to build your DVD filter graph manually, you can do so by following the basic rules of graph building discussed elsewhere in the DirectShow documentation. Generally, you should not manually add, remove, connect, or disconnect individual filters in the graph created by the DVD Graph Builder, because doing so might confuse the cleanup code.

When creating an instance of the DVD Graph Builder object, an application receives a pointer to the object’s IDvdGraphBuilder interface. Call IDvdGraphBuilder::GetFiltergraph to obtain the filter graph manager’s IGraphBuilder interface, and then call QueryInterface on IGraphBuilder to obtain IMediaEventEx. Use this interface to begin receiving events before building the rest of the graph. This will ensure that your application receives events from the DVD Navigator when it is initialized. To build the graph, simply call the IDvdGraphBuilder::RenderDvdVideoVolume method. For more information, see Building the Filter Graph.

On Windows XP Home Edition and Windows XP Professional, the DVD Graph Builder will always use the Video Mixing Renderer (VMR) in the graph, unless:

• a) the caller queries interfaces found only the Overlay Mixer, such as IMixerPinConfig2. This sends a hint to the DVD Graph Builder that the application wants to use the Overlay Mixer and not the VMR. Windows Media Player also has a dialog box option to force the use of the Overlay Mixer.
• b) the installed decoder is not VMR-compatible. During graph building, the new IAMDecoderCaps interface is used to check for the decoder's VMR support. If that is not present, the DVD Graph Builder will use the Overlay Mixer.
• c) while using a hardware decoder, the decoder cannot connect to the Video Port Manager (VPM). If a decoder cannot use the VPM, then it cannot use the VMR, and so the DVD Graph Builder then tries to build a graph using the Overlay Mixer.
• d) the display card is known to have insufficient resources and/or capabilities to support the VMR but does not correctly report this in the driver. (Some known cases are hard-coded into the DVD Graph Builder.)
• e) the connection between the decoder and the VMR fails for any reason, usually due to a lack of VRAM to create the necessary surfaces. In these cases, the DVD Graph Builder switches off VMR use and tries to use the Overlay Mixer to build a graph.