What are PQ codes and should I care?
PQ codes are the parallel data tracks that define certain aspects of CD metadata – most importantly track start, track end, pauses, and some metadata codes. Generally you don’t have to deal with these directly, unless you’re trying to do something clever like put hidden tracks before track one or whatever. CD creation software handles this stuff for you and usually hides it behind friendlier “track start†and “track end†interfaces.