Ive been converting divx & xvid to dvd's for quite a while using cce2.5 & tmpgenc, both with either 3 pass or 2 pass vbr & frameserving with avisynth. My question is how come when i work the bitrate out for the length of the film and encode sometimes i can get it to fill a full dvd and other times it might only come out at about 2-3 gig? my worst xvid to dvd conversion was undercover brother dvd screener that only comes out at 702meg no matter what bitrate i use. Any help would be appreciated i know divx to dvd isn't the best method to make dvd's but i can usually get pretty acceptable quality, i would just like to use all the dvd space to get the best results possible

Thanks