DivX FAQ - How many versions are there of the DivX codec ?
There are in fact 2 major codecs, both name the "DivX codec". But the newer one, which used to be part of the open-sourced project at Project Mayo (now under a licensing scheme), is more commongly referred to as "DivX For Windows/Linux/Mac ...", whereas the orginal codec is sometimes referred to as the "DivX ;-) Codec". The version number of these 2 major codecs are also different - the original being 3.xx, while the new ProjectMayo codec has a version number of 4.xx.
Most older/existing movies are encoded with "DivX ;-) Codec", since the new DivX 4.x codec is still being developed.
The original DivX 3.xx codec is based on Microsoft's MPEG-4 V3 codec (ASF was based on MPEG-4 V2). The reason why the codec was "hacked" and re-distributed is because Microsoft's codec did not allow one to encode to AVI (they only wanted people to encode to ASF/WMV), which is far from being convenient. The DivX 3.xx codec also includes hacked versions of a MP3 codec and a WMA codec. The AnglePotion, MPEG-4 and SMR codecs are all in the same boat. There is also a VKI (Scene Detect) patch that will insert keyframes at scene changes for you automatically, which will improve picture quality.
The new DivX 4.x codec has nothing to do with Microsoft - it has been developed entirely from scratch, and is still under development (hence less then perfect compatibility/efficiency/quality). In time, the DivX 4.xx codec will completely replace the 3.xx codec, but for now, the 3.xx codec offers better compatibility/efficiency/quality. The 4.xx codec is compatible with the 3.xx codec, but may have performance/quality problems (the same is not true in reverse - the DivX 3.11 Alpha codec is not compatible with the DivX 4.x codec).
Note that both codecs can be installed together, and 3.11 encoded files will playback with the DivX 3.11 Alpha codec and 4.x encoded movies will playback with the DivX 4.x codec (this is true unless otherwise specified during the DivX 4.x setup, which allows you to playback all 3.11 Alpha movies using the 4.x codec)
