I have some mpeg-2 (.mpg) files that are Upper-Field-First. I loaded them into PE10 using a FLASH/HDD setting (assumes Upper 1st). I then edit & make .mpg output files. The default NTSC DVD setting is Lower Field First. The output comes out slightly blurry, and degrades in quality for each successive generation made.
However, if I load the same Upper-Field-First mpeg file into a project with setting for DV which assumes Lower Field First, then use the Reverse Field Dominance setting in the timeline options, the output for a Lower-Field-First .mpg looks great. You can hardly notice any degradation for the re-encoding, even when I do a 5% zoom.
So why the difference? PE10 seems to manage the Reverse Field option a lot cleaner than the codec for .mpg output encoding a source file Upper to an Output file in Lower format.