I have an ACL harddisc recorder that allows me to
1. load in DVDS &
2. load in mpeg files

Mpeg files can show thumbnails making it eaiser to pick the videos so I used to convert the DVDs from .VOB to .mpeg (by either simply renaming or with MPEG Streamclip) and then load them into the HD recorder.

But I now have some NTSC DVDs which are interlaced (line B). I change them from .vob to .mpeg and the resulting .mpeg video is very ugly and the interlaced lines are all shown when played via the HD recorder on my plasma TV.

I tried to convert the mpeg files to PAL spec using line A, line B and whole field but still can't remove the interlacing in the resultant playback on TV. The original DVD when loaded into the recorder will play normally though.

How may I improve the mpeg videos quality?
Interestingly not all the NTSC DVDs with the same spec have this problem. Any ideas why?