Re: [dvd::rip] Re: Deinterlacing

On Mon, 2005-07-25 at 22:26 +0200, Sylvain wrote:
> But then, why are deinterlacing method so cpu intensive ?

For a source that is PS (progressive scan) it shouldn't be in fact I
wouldn't think, unless transcode (i.e. it's mpeg library) is doing the
artificial interlacing, producing an interlaced stream and then
de-interlacing that.

If it is smart like mplayer is (which I would think it would be) and can
see that the source is really already PS and just "flagged" to be
interlaced with a 3;2 pulldown when output, it should not be at all
expensive to de-interlace as there is no de-interlace needed in fact.

> if I understand correctly, they just have to ignore a flag ?

Yeah, you do seem to understand correctly.  It is a very valid question.

> Or are some dvd "artificially interlaced" and others "really
> interlaced" ?

Oh, I think this is the case, and a third case, where the original
material is shot interlaced, on video tape for example.  I don't have
any idea how many "movie" DVDs are "hard" interlaced vs. soft though.  I
would hope little, or rather none.  As I said before, I can't imagine
why a hard interlace would be used short of a process engineering
mistake or misunderstanding.

> > And indeed, my tests on mplayer playing a VOB file from a film does
> > indicate that there is no interlacing going on.
> > And indeed, a DVD player outputting to a progressive display should not
> > do the artificial interlacing and should just present the original 24fps
> > progressive content unaltered.
> > 
> > So with a good player, if you are seeing interlacing artifacts, the
> > source material was probably recorded on video tape originally and
> > interlaced at that point.
> > 
> >   
> "mplayer dvd://1" with no option sure show me an interlaced video with
> my "Abyss" dvd, while everything is fine with "Apocalypse Now" as an
> example.

Do either give you the:

demux_mpg: 24000/1001fps progressive NTSC content detected, switching
framerate.

message from mplayer?  That is a sign of an MPEG that is flagged to be
interlaced but is not actually interlaced.

> Same with xine.
> Sometimes, on the same dvd, the movie is not interlaced when I play it
> using mplayer, while the bonus are.

Yeah, a lot of the non-movie (i.e. interviews, etc.) on DVDs are truly
interlaced as they are shot on video tape rather than film.  For those,
if you want a PS copy of it, you do need to ask for a CPU intensive
de-interlacer to be used on them.

> Anyway, thanks for the whole explanation :)

NP.

b.
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