Description of Windows Media Audio/Video Playlist Files

This article describes Windows Media Audio/Video Playlist metafiles that have an .asx, .wax, .wvx, or .wmx file name extension.

Windows Media Audio/Video Playlist metafiles are text files that provide information about a file stream and its presentation. Windows Media metafiles refer to other Windows Media files (files with the .wma, .wax, .wmv, .wvx, .asf, or .asx file name extension). You can use a metafile to list a group of media content files that you want to play in sequence, insert advertising or special interest clips into a presentation, or play clips one after the other with minimal buffering time or interruption between the clips. The metafiles contain instructions and references that a player, such as Windows Media Player, can use. When you click a link to a metafile, Windows Media Player downloads and opens the metafile, and then locates and streams the Windows Media file or files that the metafile refers to.

Windows Media metafiles are based on the XML syntax. They can also use the ANSI or the UNICODE (UTF-8) formats. They are made up of various elements and their associated tags and attributes. Each element in a Windows Media metafile defines a particular setting or an action in Windows Media Player. To work, some elements must be located in a specific position in the file relative to other elements. Some elements have mandatory tags and attributes that must be defined in the Windows Media metafile.

The Windows Media Player 9 Series SDK provides an overview and programming guide sections, and a full reference section on metafile element tags, their attributes and values, and special conditions related to each element. For additional information about Windows Media Audio/Video Playlist metafiles, visit the following Microsoft Web site: