Windows Media formats - technical definition

Windows Media formats are supported in many software and hardware-based players as well as Microsoft's own software-based Windows Media Player. The foundation container format for Windows Media is the Advanced Systems Format (ASF) file, which holds audio, video, meta-data (titles, author, etc.), indexes and scripts.

WMA (Audio) and WMV (Video)
When Windows Media audio codecs are used, the resulting file is given a .WMA extension. When Windows Media video codecs are used, files have a .WMV extension. For non-Windows codecs, the .ASF file extension is used, and WMA and WMV files can be renamed with the .ASF extension for compatibility with earlier players. See WMA Lossless.

Streaming
Windows Media audio and video files can be downloaded intact and played, or they can be streamed from a Web site when used in conjunction with Microsoft's Windows Media Services on a Web server. In fact, ASF originally stood for "Active Streaming Format," but was changed to Advanced Systems Format to eliminate the streaming-only connotation.

Metafile Formats
Windows Media provides XML-based metafile formats for holding playlists, content descriptions and the location of the ASF, WMA or WMV file on a local or remote server. These files are called "redirectors" (see below). See Windows Media Services, Windows Media Rights Manager and Windows Media.

   WINDOWS MEDIA PLAYER MEDIA SUPPORT

   File
   Extension  Medium

   Windows Native A/V Formats

   WAV        Audio (lossless)
   AVI        Video
   ASF        Audio/video (non-Windows codec)
   WMA        Audio (regular & streaming)
   WMA        Audio Lossless (see WMA Lossless)
   WMV        Video (regular & streaming)

   Playlists
   Windows Metafile Formats (Redirectors)

   ASX        All formats
   WAX        WMA files
   WVX        WMV files
   WPL        Client-side playlist

   Non-Windows Formats Supported by
   Windows Media Player

   MP3        MPEG audio
   AU         Unix audio
   SND        Unix audio
   AIFF       Macintosh audio
   MID, RMI   MIDI music
   MOV, QT    QuickTime video
   MPG, MPE   MPEG video
   VOB        DVD