Inserting Native Stream Formats Into ASF Files (QASF)

[The feature associated with this page, Windows Media Format 11 SDK, is a legacy feature. It has been superseded by Source Reader and Sink Writer. Source Reader and Sink Writer have been optimized for Windows 10 and Windows 11. Microsoft strongly recommends that new code use Source Reader and Sink Writer instead of Windows Media Format 11 SDK, when possible. Microsoft suggests that existing code that uses the legacy APIs be rewritten to use the new APIs if possible.]

By default, the WM ASF Writer expects uncompressed audio and video streams on its input pins, and uses the Windows Media Format SDK to access the Windows Media Audio and Windows Media Video codecs, which compress the streams. But the ASF file container can be used for any type of data. By placing digital media data into an ASF file container, you can add features provided by ASF, such as metadata and digital rights management (DRM), without having to transcode your content.

To create an ASF file that contains content that is not Windows Media–based, the application must compress the stream in the filter graph upstream of the WM ASF Writer and bypass the WM ASF Writer's compression mechanism by calling IConfigAsfWriter2::SetParam as follows:

pConfigAsfWriter2->SetParam(AM_CONFIGASFWRITER_PARAM_DONTCOMPRESS,TRUE,0)

Then configure the filter with the desired profile. It is essential that the media type of the input stream exactly matches the format in the profile. In some cases, it may be necessary to examine the input stream's format, and create a custom profile to match it. For more information, see To Create ASF Files Using Third-Party Codecs.

When you connect the WM ASF Writer to the upstream filter, use the IGraphBuilder::ConnectDirect method. Do not use any "intelligent connect" methods such as IGraphBuilder::Connect or IGraphBuilder::RenderFile to connect the filter because this will disable the filter's "bypass compression" mode.