<P> A WMV file uses the Advanced Systems Format (ASF) container format to encapsulate the encoded multimedia content . While the ASF can encapsulate multimedia in other encodings than those the WMV file standard specifies, those ASF files should use the . ASF file extension and not the . WMV file extension . </P> <P> The ASF container can optionally support digital rights management using a combination of elliptic curve cryptography key exchange, DES block cipher, a custom block cipher, RC4 stream cipher and the SHA - 1 hashing function . </P> <P> Although WMV is generally packed into the ASF container format, it can also be put into the Matroska or AVI container format . The resulting files have the . MKV and . AVI file extensions, respectively . One common way to store WMV in an AVI file is to use the WMV 9 Video Compression Manager (VCM) codec implementation . </P> <P> Windows Media Video (WMV) is the most recognized video compression format within the WMV family . Usage of the term WMV often refers to the Microsoft Windows Media Video format only . Its main competitors are MPEG - 4 AVC, AVS, RealVideo, and MPEG - 4 ASP . The first version of the format, WMV 7, was introduced in 1999, and was built upon Microsoft's implementation of MPEG - 4 Part 2 . Continued proprietary development led to newer versions of the format, but the bit stream syntax was not frozen until WMV 9 . While all versions of WMV support variable bit rate, average bit rate, and constant bit rate, WMV 9 introduced several important features including native support for interlaced video, non-square pixels, and frame interpolation . WMV 9 also introduced a new profile titled Windows Media Video 9 Professional, which is activated automatically whenever the video resolution exceeds 300,000 pixels (e.g., 528 px × 576 px, 640 px × 480 px or 768 px × 432 px and beyond) and the bitrate 1000 kbit / s . It is targeted towards high - definition video content, at resolutions such as 720p and 1080p . </P>

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