Windows Media Video (WMV) is a generic name for the set of 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 (WMV7), Microsoft has used its own non-standard version of MPEG-4. The video stream is often combined with an audio stream of Windows Media Audio.
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 usually found in the AVI file container when encoded with Microsoft's 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.