by FrikaC » Wed Dec 29, 2010 8:42 pm
It is not a universal format. The PG in the name literally stands for "Prydon Gate"
The format is the raw values sent to the parm encoder in the game (in single player, without support for external files, all the information is encoded on parms for the pgf files and on cvars/serverflags for the pgg files).
The best reference is the QuakeC code itself.