New to video editing. encoding with 2 different resolutions

[mirkosp]

Actually it does. Resizing changes the PAR, cropping changes the DAR. Video basics really.

But what if one resizes so that the par is identical or crops certain precise amounts which leave the dar identical?

[Cannonaire]

I don't really see a problem with resizing the 720p footage in the way that Kariudo recommended. I tried out the method myself because I wasn't familiar with resizing in Virtualdub; while it's not my method of choice, it did work just fine and it kept the same PAR because of the options recommended.

I would just like to highly recommend that the 480p footage also be resized in order to match the Pixel Aspect Ratio (PAR) of the resized 720p content, otherwise half your footage will look stretched and the other half will be cropped in a weird way. You can read the info on cropping/resizing in a guide here: http://www.animemusicvideos.org/guides/avtech31/
It's not precise, but it's pretty well standard around here. If you care enough to use exact numbers for resizing, just ask and I can definitely help you out, I just don't want to derail this thread. Also, thanks to this thread and some experimentation, I now know how to do exact resizes in Virtualdub based on the numbers given by the AR calc. If you don't want to use avisynth yet, I can tell you how to do the resizing in Virtualdub. Thanks!
AR Calc: http://ps-auxw.de/cgi-bin/ar-calc.pl

[OMGapotato]

thanks. i've been reading the A&E technical guide and i must say, for someone who isn't well versed in video technology, it was really insightful. thanks to whoever made it.

i'm probably going to use avisynth since the guide requires the use of it. i'll probably post questions about resizing later after i'm done with the guide. thanks for the calculator though. i'm sure i'll need that later