Actually, here's a fun experiment for you to try, with the numbers adjusted for PAL/SECAM material
Code:
A=mpeg2source("whatever.d2v").bob()
B=mpeg2source("whatever.d2v").converttorgb(interlaced=true).separatefields()
C=B.selecteven().bicubicresize(720,576,src_left=0,src_top=0.25,src_width=720,src_height=288)
D=B.selectodd().bicubicresize(720,576,src_left=0,src_top=-0.25,src_width=720,src_height=288)
E=interleave(C,D)
Compare(A,E)
You'll find naught but rounding errors