Where can I find missing audio codecs for my Mac?

When you try to play a DivX encoded file on your Mac and there is no audio, it may be because you are missing one of the following:

AC3 Codec (for PowerPC only) : http://mac.softpedia.com/get/Audio/AC3-Codec.shtml

MPEG2 which can be found by searching the internet.

To check which audio codec your file is encoded with - see 'No audio or audio is distorted with DivX movie playback on a Mac' for reference.