Image Processing Reference
In-Depth Information
The files are created through the Windows Media SDK and are structured according
to a profile. These profiles are created and stored in XML files having the .prx file exten-
sion. The metadata support is based on ID3 tagging protocols.
The file container supports files as large as 17 million terabytes (TB), which is way
beyond anything you are likely to ever want to put in there.
Table 16-3 lists the file extensions used for ASF files depending on what is stored
in them.
You can find out more at the Microsoft Web site on the pages that describe ASF and
a TechNet security bulletin.
File-Related Gotchas
Sooner or later you are going to run into some file problems, and almost certainly they will
have to do with file sizes or the space available to store them.
File-Conversion Issues
Sometimes converting from one format to another loses quality for no apparent reason.
Going from one format to a supposedly better one might result in blocky or washed-out
looking pictures. It might be the conversion software at fault so try an alternative tool to
see if the compression is any better.
Sometimes this will not make any difference because the tools are built on top of a
common application programming interface (API) and the only thing you are changing is
the user interface.
2-GB Limit on Some Systems
Beware of the 2-GB file-size limitation. Some years ago, operating systems and PC hard-
ware designs eliminated this, but many applications did not. Some still have this issue,
and you have to be careful how you import movies into these packages.
Table 16-3 ASF File Extensions
File extension
Audio compressed with the Windows Media Audio codec
Audio and video compressed with the Windows Media Audio and
Windows Media Video codecs
Content created with other codecs
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