Any transcode gurus out there?

I'm trying to convert a bunch of MPEG1 & 2 videos to DVD. The DVD plays and the picture is OK but some clips have no audio and some clips are playing too fast.


Here is the commands I'm using:

transcode -i FILE.INPUT -D 0 -y mpeg2enc,mp2enc -F 6 -Z 720x480 -o /tmp/outputfile (I've also tried -F 8)
mplex -f 9 -o /tmp/FILE.mpg /tmp/outputfile.m2v /tmp/outputfile.mpa

Can someone help out a n00b?

Thanks!