For those of us in PAL land who seldom work with NTSC.
I had a PAL video converted to NTSC by a post house to a .mov file and then made a Mpeg dvd file from it using media encoder. The results were very poor with jagged edges to all the detail.
I tried the same Mpeg encoding with AVIsynth and HC encoder and I got the error message that the image height was wrong. It seems that NTSC broadcast is 486 high but for dvd it needs the be divisible by 16 so the height becomes 480. The Prores file from the post house was 486 high and Media encoder was re-scaling this to 480 for the dvd. It was this scaling that was creating all the artifacts. I just cropped 6 lines from the picture and all was fine. I'm sure editors that work with NTSC all the time know this but it's worth remembering for the rest of us.
FCP converts have a difficult time and I don't know if you belong to that category, but the sooner people understand that you edit natively in Pr and forget about QuiRcktime, ProRes and other intermediates, the easier it gets.
You seem to forget that Prores is often the native format. The post house that did my Alchamist conversion masters to FCP and this was sent as a Prores to me. There was no other format.
A lot of the stand alone hard disc recorders also record to Prores.
or the standard camera format, like the Atomos Samurai.