iDVD encoding questions

[L.Cornelio]

i am wodering if someone can speak to the encoding / compression  options 
on iDVD -

I havent tried it, I assume there is only a single quality mpeg2 encode.


I am told that windows Pinnacle Studio Version 8.3 will automaticcaly 
adjust compression based on the length of the movie to fit / take up  a 
single DVD, so for example a 60 min film gets less compression than 90 
min to fit on same space.


So that makes me wonder if the 'default' for iDVD is for 90 min worth of 
compression no matter what length film you choose. Does this make sense? 
Does it matter? Am I wrong about compression variables? What MAC product 
allows variables in the encode esp. amount of compression. What if i 
wanted to burn a 100 min DVD - cant use iDVD so what is recommended?
Sorry fpr the newbie questions, looking forward to new emac in my 
classroom. And I had to fight for it - the school is 90% windows!