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, without the DirectX 9 runtimes, the DVD Graph Builder will always use the Video Mixing Renderer 7 (VMR-7) in the graph, unless:

• 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.
• 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.
• while using a hardware decoder, the decoder cannot connect to the Video Port Manager (VPM). If a hardware 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.
• 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 specifically excluded by the DVD Graph Builder.)
• 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.

On any system with a software MPEG-2 decoder and the DirectX 9 runtimes installed, the application should attempt to create the DVD Graph Builder with the AM_DVD_VMR9_ONLY f lag in the dwFlags parameter of IDvdGraphBuilder::RenderDvdVideoVolume. This method instructs the DVD Graph Builder to use only the Video Mixing Renderer 9 (VMR-9). When this flag is specified, if the graph builder cannot use the VMR-9 in the graph due to any reason, for example if

• the video card's capabilities are not adequate for VMR-9, or
• the decoder is not VMR-9 compliant, or
• the only video decoder is hardware based (uses video port or analog overlay), or
• there is not enough display resources ( for example, low VRAM, known bad VGA cards, or too high resolution)

then RenderDvdVideoVolume will fail, and the application has the option of attempting to build the graph with the VMR-7 or the Overlay Mixer.

Also, since the VMR-9 does not support video ports or analog overlays, if the filter graph is using a hardware MPEG-2 decoder, especially for video, then the application must use the Overlay Mixer in all such cases.

An application can also call IDvdGraphBuilder::GetDvdInterface for any of the VMR-9 interfaces, which will result in the VMR-9 being inserted in the graph. The application then has an opportunity to configure the VMR-9 before starting to build the graph.