Windows Media Video (WMV) is a generic name for the set of streaming video technologies developed and controlled by Microsoft. This does not necessarily define what technology it uses -- from version 7 (WMV7) Microsoft has used its own non-standard version of MPEG-4. The DivX video format is originally based on cracked WMV codec. Usually WMV video is packed into an ASF (Active Streaming Format) container.
WMV features digital rights management facilities.