[MEncoder-users] How does one interlace progressive content?

[Reimar Döffinger]

Hello,
On Tue, Aug 14, 2007 at 02:03:25PM +0200, Pierre Catello wrote:
> 2007/8/5, Loren Merritt <lorenm at u.washington.edu>:
> 
> > No one makes interlaced dvds from progressive content; if a progressive
> > source exists they make progressive dvds instead. Though sometimes you see
> 
> Mmmm, I'm pretty sure to have seen some PAL DVD made from progressive
> source and encoded as 576 interlaced (alternate fields).

What means "encoded as 576 interlaced"? They could have simply used the
interlaced motion estimation and interlaced dct, that works perfectly
fine for progressive data, it just wastes lots of bits. That kind of
thing can happen easily if you have the usual person without a clue
using an encoder that is crap (and looking at some of my DVDs, there are
a lot of both in that field - but with most using dual layer DVDs
that's not really much of a problem).
If you mean that the fields actually contained data from different
moments in time, there is no even remotely sane way to generate that
from a progressive source with the same frame rate.
Things are of course different if the progressive source has a different
frame rate - though unless the source frame rate is exactly a multiple
of the destination you will still get a mixture of "interlaced" and
progressive frames.

Greetings,
Reimar Döffinger