CompuServe Messages

I am looking for some info on cd-rom xa and the adpcm chip set….is this chip set a part of cd-eom xa compatibility or does it have to be added to the cd-rom drive when purchasing? I am asking this for a colleague of mine and so if the question makes no sense to you it's probably because I know nothing about the topic in question!!! Any takers out there familiar with this area??/ Owen Wheaton