[MPlayer-users] Re: slightly confused by mencoder output

[Matthias Wieser]

Am Mittwoch, 14. September 2005 04:10 schrieb Rich Felker:
> On Tue, Sep 13, 2005 at 10:59:51PM +0200, Matthias Wieser wrote:
> > Am Dienstag, 13. September 2005 09:11 schrieb RC:
> > > On Mon, 12 Sep 2005 22:37:41 +0200
> > >
> > > Matthias Wieser <mwieser at gmx.de> wrote:
> > > > Or any other supported resolution if you have a saa7134 card
> > > > because the saa7134 chip has a not-so-bad deinterlacer.
> > >
> > > Does it do ivtc too?
> >
> > I don't know. I'm living in a PAL country :-)
> > I think it's doing only deinterlacing.
> >
> > > If not, it would be a good idea to mention this
> > > is PAL-specific...
> >
> > Deinterlacing is not pal-specific. You can deinterlace ntsc as well
> > but sometimes it would be better to use ivtc. But that's a
> > disadvantage of NTSC, not a PAL-speciality.
>
> No, this is a lack of understanding on your part.

Nope.

> Both PAL and NTSC 
> are interlaced formats which use pulldown to display film content.

Right, the interlaced format of NTSC is exactly the reason I wrote "You 
can deinterlace ntsc as well".

> NTSC just happens to be 3:2, whereas PAL is 2:2

That's the reason I wrote "but sometimes it would be better to use 
ivtc" [for NTSC].
I wrote "sometimes" because not every broadcast your TV Card receives is a 
film with 3:2 pulldown.

The disadvantage of ntsc is that you nearly always need to process the 
video. For PAL you only have to use a deinterlacer if it's not film 
content.


> (with horrible speed-up)

That's a bit esoteric because there are filters which are able to speed up 
the audio without changing the pitch. TV networks do use these. And I 
don't know anybody who is able to detect that motions are played 4% 
faster than normal.


> or 2:2:2:2:2:2:2:2:2:2:2:3. :) Also there's no guarantee 
> that 2:2 PAL is in phase with the field pairing of the capture device.

There is no formal guarantee but it works for 99,...% of all cases. To be 
precise: I have never had any captured video which was out of phase. Oh, 
that's not 100% correct, I had one bad capture but that was bacause of a 
bug in the saa7134 kernel module. An updated kernel solved that problem.

> Basically you always need some sort of inverse pulldown for film
> content, regardless of whether you have NTSC or PAL.

If you have PAL it's nearly always bad to use one of mplayers inverse 
pulldown filters. It's nearly always the right thing to use no video 
filter (film content) or to use a deinterlacer (You may call the latter 
one a special inverse pulldown filter...).

> It's just that 
> sometimes with PAL you get lucky and the capture device/broadcast/dvd
> field pairing happens to give you the desired frame matching.

Replace "sometimes" by "nearly always" and it corresponds with my 
experience.

MAtthias