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11b. MPEG4 (DivX, XviD, ASF, WMV)
MPEG4 Codec [Keikai, Netgear, ed.]
MPEG4 is the basis for many of the most popular codecs, including:
While originally popularized on Windows. Many of these codecs are now available on other operating systems.
Because of the significant quality/filesize ratio of properly encoded MPEG4 files, it has become the primary codec class used in AB(M)A.
Due to the many different MPEG4 codecs, however, it is often necessary to perform many codec installations in order to support them all.
MPEG4v1, v2, v3 [darkwire, Keikai, ed.]
These three codecs were the first MPEG4 codecs used. Because better codecs that are also freely available are now present, these codecs should no longer be used for new encodes. It is, however, still necessary to install some or all of these codecs depending on your operating system to support older encodes.
The official Microsoft links are as follows:
The best site for practical information and codec downloads for MPEG4 is http://www.undercut.org/msmpeg4/.
DivX [Keikai, darkwire, ed.]
The official DivX site is http://www.divx.com/.
DivX was originally a hack of the Microsoft MPEG4v3 codec, but has since become a completely separate codec. It is available in both free and purchased versions.
DivX is the most common codec used in the groups, although you will find several versions of the DivX codec that are all used.
The most common versions are 3.11, 4.0n, and 5.0. Officially, installing the most recent version of the codec will allow playing older versions, however, there have been complaints of lowered quality and compatibility when playing files created with the older codecs. Version 3.11 can be installed separately of later versions without much hassle. Getting versions 4 and 5 to coexist on a single computer is very difficult.
The official XviD site is http://www.xvid.org/.
When DivX became a commercial enterprise, an open-source project was created entitled Project Mayo. One of the offshoots of Project Mayo is XviD. XviD is an open-source implementation of the DivX codec. The codecs are now, more or less, independent of one another.
XviD is generally popular because of it's open source status. It is generally considered slightly inferior in terms of quality to modern DivX, but it is still popular.
To play (decode) XviD files, you will either need to compile your own codec files or download and install precompiled binaries. The two most popular binary distribusions for Windows OSes are:
.ASF Files [The Man, Keikai, ed.]
.ASF Files are the original Microsoft attept at media-rights control. The codec used in these files is exactly (or nearly so) the same as the MPEG4v3 codec. Windows Media players are able to play .ASF files. It is also believed that the Linux avifile library is able to play .ASF files.
Because of the proprietary nature of .ASF files, creating new encodes in this format is strongly discouraged.
.WMV Files [Keikai]
.WMV files are Microsofts second, and much more successful, attempt at media-rights management. While the Windows Media codecs are still based upon MPEG4, converting from .WMV files is nearly impossible. Windows Media Player is necessary to play .WMV files.
Because of the proprietary nature of .WMV files, creating new encodes in this format is strongly discouraged.
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