[gembud] Questions Regarding GDGRIB2

I am having difficulty finding some good documentation regarding GDGRIB2. 
Specifically, the G2TBLS, G2IS, G2IDS, G2PDT, and G2DRT sections. The method to 
my madness here relates to the fact that our television graphics system will 
only recognize a few PDTs, the most common being 4.0. Since not all datasets 
use this template, I have had to use wgrib2 to manually change the PDT of a 
given dataset, and then call the variable I am working with something other 
than what it is. Sounds a little unorthodox, but as long as I know what the 
variable name is referring to, everything is fine. So, to have any chance of 
showing some of the more elaborate ensemble data on the air, I really need to 
understand the syntax behind these 5 entries. Thanks for any help anyone can 
provide. 

Greg Fishel
Chief Meteorologist
WRAL-TV
P.O. Box 12000
2619 Western Boulevard
Raleigh, NC 27606
919-821-8992