WMV was originally developed for Internet streaming. There are several proprietary codecs available for the various versions of WMV. The latest version 9 was submitted to SMPTE for standardization by Microsoft. The standard was officially approved in March 2006 as SMPTE 421M, better known as VC-1. This makes the WMV 9 format an open standard. VC-1 is one of the three mandatory video formats for the BD-ROM specifications (Blu-Ray). As such it achieves higher compression than earlier MPEG formats with Blu-Ray capacities in excess of 3 hours of playback time using standard disks.
A WMV file is usually placed in an Advanced Systems Format (ASF) container format The file extension .WMV typically describes ASF files that use Windows Media Video codecs. The audio codec used in conjunction with Windows Media Video is likely a version of Windows Media Audio (WMA). It is also possible for WMV format data to be placed in an AVI container.