I have briefly taken a look into the CDDB files that are on disc, but it isn't immediately obvious what the format is (at least, not to me). I've been having the same requirement since the player isn't hooked up to the inet.

It may be easier to just map the 'original' gracenote server to localhost via /etc/hosts and create a daemon that handles CDDB lookups via a local FreeDB database. If I have time I will put some effort into building this and share it here.

Jeroen