Well, neither Quicktime standard or Quicktime Pro can play Divx movies without the help of a third party decoder such as this or
the official Divx component.
If you've never heard of Divx, it's an MPEG-4 based format and is very popular on the web and p2p networks for long videos because of it's small file sizes. You'll usually see Divx movies with a .avi extension, perhaps you've run across some before.
Some other things to note are that with the current 3ivx D4 4.04 Quicktime plug-in, videos with mp3 audio (which are very common) have problems playing any sound at all... this was a Quicktime bug that Divx.com's plug-in was able to work around and play the mp3 audio.
However, the Divx plug-in cannot play videos in the open-source Divx format, Xvid. There is a known trick to this however by installing both plug-ins (3ivx handles the video, Divx handles the audio), but i have found that the Divx plug-in alone is more stable as the current 3ivx plug-in breaks my ability to play certain MPEG-4 .mov's in Quicktime. My hope is that the decoder plug-in in this new version of 3ivx can get around the mp3 problem, does anyone know if this is the case?
But.. on the encoding side.. which i think is what you might be asking about; this 3ivx deal (Or the official Divx one) adds an option to export to the Divx format from within Quicktime Pro... so you can take advantage of this widely used, efficient video codec.
As a side note, if you just want to play Divx movies (as opposed to also being able to encode/create them with 3ivx and Divx) you can just download
VLC or
MPlayer which are convenient because all of their codecs are built-in, so you don't have to worry about any Quicktime plug-in incompatibilities (like not being able to play Divx videos that have WMA audio.) Of course i also have a Quicktime plug-in installed so i can play most Divx vids in the Finder preview.
