althor1138 said:

Ok I did some reading and I think this is what you are after:

mpeg2source("palclip.d2v")

bob(height=480)

bicubicresize(720,480)

changefps(60000,1001)

separatefields()

selectevery(4,0,3) #use selectevery(4,1,2) for odd field first.

Weave()

This is just copied from the wiki.

EDIT: Just tested this and it seems to do exactly what you want. I fed it a pal clip and out popped a 30i clip with the exact same playing time.

Tried that, it does the strange horizontal linear shaking that every other program does. Maybe I'm asking too much? I've just seen professional DVDs of this show with stable video.