WMV which stands for Windows Media Video is a compressed video file format for several proprietary codecs developed by Microsoft. The original codec, known as WMV, was originally designed for Internet streaming applications. Since it is developed by Microsoft, Windows platforms come pre-equipped with the ability to play this multimedia format, however other operating systems do not. WMV is primarily based in ASF (Advanced Systems Format) that wraps a video bit stream. Some WMV files may also employ Windows Media Video 7 and 8 codecs. Microsoft claims that WMV 9 provides a compression ratio that is two times better than MPEG-4, and three times better than MPEG-2. Microsoft's proprietary ASF wrapper format is fully documented thus making it available for open-source communities to develop and employ their own customized codecs to other media players which do not natively support this type of format. Although WMV is generally packed into the ASF container format, it can also be wrapped in the AVI or Matroska container format. As the name implies the AVI video format has a .AVI file extension, whilst the Matroska files have a .MKV file extension. While none of the WMV codecs themselves contain any digital rights management [DRM] facilities, the ASF container format can. Since the WMV file format can be encapsulated in ASF, this enables WMV to support DRM. Windows Media DRM, which can be used in conjunction with WMV, supports time-limited subscription video services. A list of multimedia players which support WMV files include: Windows Media Player (which comes parceled with every Windows installation package), VideoLAN (VLC), and Media Player Classic (MPC). These all support the WMV format without having to install additional codecs, so you basically can download these players freely from their respective websites. VLC and MPC are available on all operating systems including MacOS and Linux etc.