Thanks for the advice again! It's clear you know what you're talking about on the subject!
...
AFAIK the main purpose of setting PAR in a mp4-type file is for the correct display of various wide screen ratios without any letterboxing (as you often get with 16:9 DVDs). Encoding black letterboxing is not good with mp4.
...-mikiem
First, to fill in anyone who doesn't know: PAR is Pixel Aspect Ratio. If the pixels of a dvd video were square the image would look squished/stretched (US-DVDs have a 3:2 aspect ratio), so DVDs have a "PAR". The pixels of a 4:3 DVD have a PAR of 8:9, pixels of a 16:9 (non-letterboxed) DVD have a PAR of 32:27.
The main reason I'm going to keep that PAR is to maintain quality (no scaling until playback). But avoiding letterboxing is also a very good reason for PAR.
I haven't had to crop anything yet, but I think I'll probably crop the letterboxes out completely and resize it slightly so that each dimension is a multiple of 16.
Regarding Nero, I've waved bye bye that that POS a long time ago, and I refuse to believe any "one stop solution" can offer anywhere near the quality:size ratio I'll get by using AviSynth and a little elbow grease.