Advanced Systems Format (ASF) Files
[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 It has been superseded by Source Reader and Sink Writer.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.]
All of the objects of the Windows Media Format SDK work with files that conform to the Advanced Systems Format (ASF) file structure. These files are referred to as ASF files in this documentation. For more information about the structure of ASF files, see Overview of the ASF Format.
Sometimes the term Windows Media file is used to describe files created by using this SDK or other Windows Media technologies. It is not accurate to call an ASF file a Windows Media file unless it contains only content encoded by using Windows Media codecs. For more information, see the guidelines for the use of the .wma and .wmv file extensions in the File Name Extension Guidelines section.
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