I'm helping a cinematographer friend put together a demo reel. Some of his material had to be pulled from DVD. So I've got a 4:3 ProRes file that I'm trying to export into a letterboxed image. So far I've tried the 'Aspect Ratio' slider under Distort (set to -33.3 and -25) and checking the anamorphic 16:9 box in the sequence settings. No matter what I do the resulting video has faint horizontal lines in it, which is especially noticeable with action and sharp edges. You'll see a woman's face but the edges will have this jagged edge appearance. At first I thought it might just be QuickTime, because I've noticed exaggerated interlacing before, but I've got other footage that was already letterboxed and it rendered out of FCP looking proper.
I used Mpeg Streamclip to rip the footage, and for everything he gave me it worked just fine, already letterboxed and no artifacts. However, this one disc resulted in more space on the bottom than the top and various other strange issues, so I just ripped it as 4:3 and thought I could squish it with FCP. Only problem is, FCP doesn't seem to want to squish without artifacts. I couldn't find any combination of settings with Mpeg Streamclip that worked. And the video looks fine during playback in FCP (even with the distortion), but once I export it's no good, and I've got my friend texting me non stop asking me what's going on. I'm at a loss, the only other idea I've got at this point is to try and playback the material straight off DVD and capture it through the patch bay...
That sounds to an interlacing issue.
There is a general misconception about that DVDs are always "Lower-first". That's not true.
You may be mixing Upper and Lower stuff, or you are rendering with the wrong field order.
Open the "Stream Info" in MPGStreamclip, and make sure which one is the correct field-order of your MPEG-2s.