In principle, the parent comment is correct about interlacing, but it's not apparent to me
that it's necessarily desirable now in 2008
A "normal" interlaced TV was the only thing in people's homes in the 1990s when DVD was
introduced. However most of the material people are actually watching on DVD, that is, movies
and high budget TV productions was shot on film (or a film-like digital process), and so no
true interlaced source exists. As a result what's actually on the DVD is essentially 24 fps
progressive scan, and the interlacing is created during playback.
[ It's possible to use the same telecine process an analog TV channel uses to broadcast a
movie, and then record the interlaced result on DVD, and in a few famous cases this has
actually been done to movies you've heard of, e.g. some releases of The Princess Bride, but
it's acknowledged that this is the Wrong Thing ]
In another decade, with CRTs gone from most people's homes, interlaced video may be solely a
legacy format. At that point approaches your choice for old home videos, where the source
material really is interlaced will be between relying on a realtime de-interlacing filter in
your DVD playback hardware or television, and doing it once with high quality software as our
Grumpy Editor elected to.