avi files are more universal than mkv

Avi is probably to simple an explanation but mkv's are not universal in that they do not have codecs to play on many devices. If you adjust the avi's codec it will play on an iPod, PS3,XBOX or any DivX or XviD player. This depends on if it is the DivX codec or XviD codec. DivX being just avi or XviD being mp4 avi. The DivX codec is good for many devices while the XviD codec is for pickier devices. However, I have noticed my DivX certified set-top DVD player plays both codecs. I have also noticed some DivX videos also have different audio formats so, is DivX really just one codec? It must depend on the audio codec as well.