More info re AT3 files in EBOOT.PBP's :
Having done a bit of testing with SoundForge 8 and AT3 sound files i have found that there appears to be a file size limit for the EBOOT.PBP.
Basically - i have been playing around with a track that lasts 3mins+ and found that this simply WOULD NOT play when built into an EBOOT. Having cut this down in stages i discovered that anything longer than 30secs just does not want to play.
Investigating this further i found that using a very small eboot (PARAM.SFO + ICON0.PNG + AT3 file - ie. Info to run, icon + music) i can only get a 30sec AT3 to play, if you then add things like PIC0.PNG PIC1.PNG etc the sound refuses to play.
Having noticed the file sizes of the EBOOT - it appears that the maximum size EBOOT that can play music appears to be approx 500KB, anything larger than this seems to prevent music playback.
(I think that an eboot larger than this would still execute ok, but it just won't play music - but i haven't actually tested this, it's not very likely is it!)
I'm still looking into getting the AT3 to loop - if anyone out there knows how let us know!
I hope you find this additional info useful - if so add to my reputation thanks
FYI using the smallest possible SFO (1kb file - just had a title) with no icons or pics - i have managed to get the total length of music upto 30.5 seconds ish (at 132kbps)
You can get more if you lower the bitrate, but the .AT3 file must be under 500kb in size (and anything less than 132kbps sounds awful!)
(I got over a min to work at 66kpbs but the sound it crap!)