[MPlayer-users] Re: [-] Re: [-] Crop before deinterlacing OK?

[Matthias Wieser]

Am Donnerstag, 7. Juli 2005 21:29 schrieb Rich Felker:
> On Thu, Jul 07, 2005 at 10:34:40AM +0200, Matthias Wieser wrote:
> > Am Donnerstag, 7. Juli 2005 03:08 schrieb RC:
> > > As long as
> > > you stick to multiples of 4 you should be fine.
> >
> > For normal PAL and NTSC broadcasts, but not for telecined NTSC
> > movies, am I right?
>
> No. It must ALWAYS be a multiple of 4 if the input is field-based.

The last part of the sentence above was meant as "sticking to multiples of 
4 is not enough for televined NTSC" because RC wrote: "Those of us using 
NTSC need to inverse telecine first, and those filters (eg. pullup) 
really do need to come before croping (or anything else)."


> > > Those of us using NTSC need to inverse telecine first
> >
> > I thought you only need to inverse teleine when capturing NTSC
> > movies. Normal NTSC TV broadcasts can be deinterlaced with
> > pp=[md|lb...], right?
>
> It depends on the content. You have to painstakingly check every
> single thing you encode.

If I do not want to do this, it should have no disadvantage to always use 
"pullup" (maybe except some higher CPU usage)?

> > >, and those
> > > filters (eg. pullup) really do need to come before croping (or
> > > anything else).
> >
> > Mplayer HTML documentation says: "[...]you must crop vertically by
> > multiples of four or else the inverse-telecine filter will not have
> > proper data." Which informations included in the TV signal are lost
> > when cropping? I think DVD has something like a soft-telecine flag
> > but TV?
>
> No, the problem is that the chroma will no longer correspond to the
> right field. If you don't understand it, just accept it. YOU MUST USE
> MULTIPLES OF 4 WHEN CROPPING INTERLACED (any field-based) CONTENT!

I do understand the multiples of four thing very well. That's why I wrote 
in my initial email that I use a vertical offset which is a multiple of 
four. What made me wonder is that RC wrote "those filters (eg. pullup) 
really do need to come before croping (or anything else)."

So: Is it ok to crop (multiple of four) before pullup or do I *have* to 
use pullup before crop? That's my question.

Thanks,
  Matthias