What DVD authoring program are you using?
If you’re using DVD Studio Pro, I always export a FCP Quicktime Reference file and then import that into DVDSP,
Before importing that file in DVDSP, I go into Preferences > Encoding. I set the average bit rate to 4Mbps and the max bit rate to 6.5Mbps.
DVDSP will automatically make the MPEG files for you.
Robert J. Grauert, Jr.
http://www.robgrauert.com