Microsoft DirectX 9.0

Reading ASF Files in DirectShow

For reasons related to backward compatibility, two source filters are available for ASF files. To create an application that reads ASF files, you will need to understand the difference between the two filters in order to use the right filter for your requirements.

Note   The following paragraph only applies if the Windows Media 9 Series runtime libraries are not installed on a system.

The Windows Media Source Filter is the filter that is called into the graph automatically when you use methods like IGraphBuilder::RenderFile or IGraphBuilder::AddSourceFilter. This is the filter that is used by Windows Media Player 6.4. This filter is geared toward network playback and provides support for fast forwarding but not rate control. For simple playback, this filter is sufficient but in general is considered legacy technology and inferior to the WM ASF Reader, which is a wrapper filter for the Windows Media Format SDK and enables applications to make use of most of the features of that SDK for Windows Media playback. The WM ASF Reader supports the IMediaSeeking::SetRate method. Values of -1 to -10 and 1 to 10 are accepted. To use this filter, you must use the COM CoCreateInstance function to instantiate it, and call IFilterGraph::AddFilter to add it to the graph. The WM ASF Reader exposes interfaces of the Windows Media Format Reader object to enable applications to program directly to that SDK when necessary.

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