Windows Media Video (WMV) is a generic name for the set of proprietary streaming video technologies developed by Microsoft. It is part of the Windows Media framework.
WMV is not built solely on Microsoft in-house technology. From version 7 (WMV1), Microsoft has used its own non-standard version of MPEG-4 Part 2. The video stream is often combined with an audio stream of Windows Media Audio.
WMV files are played by players such as MPlayer or Windows Media Player, the latter being only available for Microsoft Windows and Macintosh systems. Many third-party players exist for various platforms such as Linux that use the FFmpeg implementation of the WMV codecs.
Raw WMV video is packed into an AVI or Advanced Streaming Format (ASF) container. The resulting files may be named .avi if it is an AVI-contained file, or .wmv or .asf if it is an ASF file, but .wmv files are to be ASF files with audio/video content only.
WMV is found in the AVI file container when encoded with Microsoft's proprietory Windows Media Video 9 VCM software for Windows. Microsoft's Windows Media Player for the Mac does not support all WMV encoded files since it supports only the ASF file container.
WMV includes digital rights management facilities intended to protect intellectual property rights.
Microsoft has submitted Version 9 codec to the Society of Motion Picture and Television Engineers (SMPTE), for approval as an international standard. (As of Jan 2005, the SMPTE is reviewing the submission under the draft-name "VC-1"). This codec is also used to distribute high definition video on standard DVDs in a format Microsoft has branded as WMV HD. This WMV HD content can be played back on computers or compatible DVD players.
The Trial version of standards were published by SMPTE in September 2005. A reference decoder implementation and test sequences are also available.
WMV3, the Video part of Windows Media 9, is not supported in VLC. However there are some fixes.
If you're using Windows and have Windows Media Player 9/10 installed, VLC should be able to play these files, by using Microsoft's own files. Or, if you're using Linux, see the common problems page for a workarround.