OpenDivX is an "open" version of the DivX ;-) digital video codec. Also known as DivX 4.x.
While the original DivX ;-) was just a hex-edited version of Microsoft's MPEG-4 codec, OpenDivX is a complete stand-alone codec written from scratch.
The FOURCC appears to be "DIVX" (while old Microsoft codec video clips have code "DIV3").
This has some advantages over the "old" DivX ;-):
- Better picture quality. (Some people have reported that videos that were pain to encode properly in the original DivX ;-) were much better in OpenDivX.)
- It's legal. No Microsoft code is involved.
- There are versions for non-Microsoft platforms (Linux, for example). Yep, mplayer plays OpenDivX stuff without help from Windows DLLs.
- They're trying to adhere to the most recent MPEG-4 standards. (Microsoft codec was released before the MPEG-4 standard was frozen, thus it's incompatible with other MPEG-4 implementations.)
The codec is part of Project Mayo (http://www.projectmayo.com/). For a good "newbie" site, see http://www.divx.com/.
However, OpenDivX is not the "Open Video Codec", because while MPEG-4 is an "open" standard, it is, like all previous MPEG standards, patent-encumbered. I'm waiting for Ogg Tarkin myself, but for time being, I think I'll still stick to VCD-compliant MPEG-1 though...
Update: DivXNetworks (the corporate spin-off of Project Mayo) no longer develops the open-source version - new, optimized Windows codecs are called just DivX 4.x (without the smiley) and are closed-source. Tarkin, where art thou?
Yet another update: While the OpenDivX is down, the code is being further developed - by the XviD team, and I heard not badly either.