Audio and Video Streams

[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 It has been superseded by Source Reader and Sink Writer.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.]

The most common types of streams used in files created by using the Windows Media Format SDK are audio and video streams. Digital representations of audio and video data are complex and take up large amounts of memory. Under most circumstances, both audio and video are compressed before being added to an ASF file. Compression is accomplished using a compressor/decompressor (codec).

Several Windows Media codecs are included with this SDK, and they provide excellent quality compression for digital media. For more information about the Windows Media codecs, see Codec Features. Many other codecs are available from various sources. You can use whatever codecs you like when creating ASF files, but only the Windows Media codecs are directly supported by the objects of this SDK. To use other codecs, you must compress samples and pass them to the writer object as arbitrary data.

The most important distinction between audio or video streams and arbitrary streams is that streams containing Windows Media audio or video data are validated by the objects of the Windows Media Format SDK. Arbitrary data streams are not validated automatically, and should be checked for integrity by your application.

The properties of an audio or video stream are described in the profile used to create the file.

Related topics

Arbitrary Streams

ASF File Features

Working with Profiles