Microsoft...
WMV (file extension .wmv)
Microsoft’s Windows Media Video (.wmv) is a format for video files that Microsoft hopes will become the universal standard for all digital video, including for use on future high-definition variants of the DVD. WMV has been through a number of releases, all requiring separate codecs to be installed on the device used to play them. The most recent is WMV version 10. The WMV10 codec is actually very good. Unfortunately, use of the later versions of WMV has been encumbered by aggressive "digital rights management" features, created by Microsoft in an attempt to enlist the support of the film studios (who are paranoid about piracy) to make WMV a replacement for MPEG-2 for HD-DVD, cable TV distribution, and all other digital video applications.
Microsoft probably regret
making the original AVI format too open to the creation of third-party codecs that
can be associated with Windows Media Player, allowing users to play
non-Microsoft digital formats. They have started to try to take control of
codec deployment. (See below.)
Initially the WMV format was not widely used.
However, its brother, WMA (.wma, Windows Media Audio) did a lot better, probably because people’s
suspicion of Microsoft is exceeded by their disgust at the way RealPlayer (the biggest competitor to Windows
Media Player) takes over their PCs and starts opening up at every possible
opportunity. Amazon/CDNOW now offers
audio clips of CD tracks in both RealPlayer and WMA format (although the BBC,
for some reason, seem hell-bent on using only RealPlayer for listening to radio
shows).
To save face on the initial slow uptake on WMV, Microsoft “enveloped” WMV and WMA within
ASF. However, now that the Microsoft publicity machine has convinced
everyone that WMV is the best thing since sliced bread, the WMV
"brand" seems to be being more heavily promoted than ASF.
ASF (file extension .asf)
Microsoft’s
Advanced Systems Format (ASF) is, according to Microsoft:
“an extensible file format designed to store multimedia data. It supports streaming data delivery over a wide variety of networks and protocols
as well as local playback. ASF supports advanced multimedia capabilities including extensible media types, component download, scaleable
media types, author-specified stream prioritization, multiple language support, and extensive bibliographic capabilities, including document
and content management.”
Basically, you do not need to know how an “.asf” file is encoded in order to play it using Windows Media Player. The file will contain, within itself, a definition of how it has been encoded – either with a Microsoft codec like WMV or WMA, or with a codec supplied by “approved” third parties. It is not clear why this is a big benefit to users, since Windows Media Player will already play any file for which a Microsoft-provided codec is present. It will also play any file for which a third-party codec is present, regardless of whether this codec is on Microsoft’s “ASF recognized codec list” or not. It looks as though ASF was just a way of forcing everyone to do things Microsoft’s way.
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