I've been encoding video content from DVDs (mostly letterboxed 16x9 fit into a 4x3) using mpeg streamclip. I'm making them into prores files to edit in FCP. If I choose 720x480, streamclip says no scaling will be performed. If I choose 640x480 it says scaling will be performed. In reality isn't there actually no "scaling" involved, just the rectangle pixels being translated into square ones, right? Is there any information being tossed out as compared to just doing a straight 720x480 encode? I've done extensive comparisons and it doesn't seem like it. I just want to make sure.
I guess it's best to explain in detail why I'm encoding to 640 instead of 720. I'm trying to keep the workflow as simple as I can for the individual I'm preparing the clips for. With him starting with 640x480 he just has to export as Quicktime Movie and then bring that into streamclip and convert to h.264 for the web. So he doesn't have to fiddle with any pixel aspect ratio business anytime he is working with the stuff.
Now most of these are destined for the web. But I was curious to see how they would look if taken all the way to a burned DVD. I thought it would be complicated and would have to manually change pixel ratios/resolutions. To my surprise, all I had to do was export as Quicktime movie from FCP, put it in compressor, added one of the DVD droplets, and burned it in DVD studio pro. The quality seemed to hold well and the aspect ratios stayed correct. My question at this point is is there any quality advantage when you get to the DVD stage and you started with 640x480 stuff as opposed to 720x480?
That explanation is probably going to confusing but all the questions really boil down to this: is there any quality loss going from 720x480 (non-square pixel ratio, or ntsc) to 640x480 and vice versa?