DivX is a package that includes all the DivX codec, player, utilities, and documentation that you need to play DivX files. DivX codec is based on the MPEG-4 compression standard. This codec can reduce an MPEG-2 video (DVD format) to ten percent of its original size. DivX is a digital video compression technology based on the ISO MPEG-4 standard.

Changes:

Added a new high-quality psychovisual mode
The decoder has been rearchitected and is now 10 to 30% faster on all CPU platforms
The decoder now supports automatic post-processing during video playback
Added new features to the rate control modes of the encoder
Redesigned encoder GUI
Improved DivX 3 compatibility
Improved Performance of Nth Pass strategy planning performance
Fixed various bugs

http://download.divx.com/divx/DivX51Bundle.exe