AVI is a Microsoft format that Mac OS X doesn’t read, so how do you make it work:
VLC Player is a cross platform application with a mac version available for download from the VLC website. [I've found that mplayer is there, but seems to hang and doesn't work well at least on Leopard, 10.5.5]
Several third party plug-ins are available to allow users to watch .avi files using Apple’s native multimedia media program. These are installed into the QuickTime plug-ins folder and usually require little or no setting up.
* Perian. Currently the best and most all-encompassing Quicktime plugin that will guarentee to play almost any codec within an AVI file.Includes support for MS-MPEG4 v1 & v2, DivX, 3ivX, H.264, FLV1, FSV1, VP6, H263I, VP3, HuffYUV, FFVHuff, MPEG1 & MPEG2 Video, Fraps, Windows Media Audio v1 & v2, Flash ADPCM, Xiph Vorbis (in Matroska), MPEG Layer II Audio, AAC, AC3 Audio, H.264, MPEG4, and VBR MP3, (i.e loads of Codecs)
- Flip4Mac. A free solution, offering playback of AVI, ASF, ASX and most importantly non-DRM protected WMA and WMV files. Microsoft site