In searching for some needed codecs for QuickTime to play avi files ripped from DVDs on my Macbook Pro, I ran across Perian ‘The swiss-army knife for QuickTime’. Perian includes video and audio codecs for many common formats.
It’s simple to use! Download the disk image, open it, double click the Perian.prefPane icon and all the components are automatically installed in the correct directories. All the video and audio plays properly for me.
Hats off to the Perian Project Team for a great job!