[mythtv-users] Interlacing [was: Pvr250 issues - any suggestions?]
Brad Bitterman
bitter at staticemi.org
Mon Apr 19 15:26:37 EDT 2004
Interlacing is still being specified today for HD. You have 1080i which is
540 lines per field. I agree that interlacing is annoying. Has any one ever
notice the difference in quality between 1080i and 720p?
I wouldn't think that 1080i video would be much better then 720p. Especially
for fast motion video....
- Brad
-----Original Message-----
From: mythtv-users-bounces at mythtv.org
[mailto:mythtv-users-bounces at mythtv.org] On Behalf Of Nick Craig-Wood
Sent: Monday, April 19, 2004 2:51 PM
To: Discussion about mythtv
Subject: Re: [mythtv-users] Interlacing [was: Pvr250 issues - any
suggestions?]
On Mon, Apr 19, 2004 at 01:34:45PM +0200, Gert van der Knokke wrote:
> Nick Craig-Wood wrote:
> >Well there is always the vertical blank interrupt! That worked fine
> >for avoiding tearing back in the bad old days (eg Atari ST!) for
> >games...
> >
> True, but which on which vertical blank is the interrupt generated ? The
> TV out or the VGA vblank? :-)
A good point! I was thinking of monitor output really as with TVout
one really should be able to do it properly...
> (With the Atari.. hmm, good old days.. it was easy as you had only
> one output.. but then some PAL games couldn't run on NTSC systems
> because there was less CPU time between Vblanks... ) Since the
> images from a PC VGA/TV-out are not in sync (due to the conversion
> from VGA to TV-out) it's gonna be difficult..
Yes including TVout is difficult!
> I must say that the TV-output of the Asus Pundit with the Winischofer
> drivers has no visible tearing even though my monitor output
> (simultaneous) runs at 75 Hz (which could explain it as this is 1.5
> times the Vsync of my little Sharp PAL LCD beamer...)
The TVout that I've played with has not showed any problems either...
Some of the TVout circuitry is suprisingly clever!
> >You'll have to display some input frames for longer than others to
> >make the 25/30 fps, interlaced to 50/60 fps into the 70-100 fps
> >output, but from my own experiments at changing the frame rate of
> >video I know this isn't very noticeable.
> >
> You'll get jerky motion if you display some frames longer than the
> others, especially with fast video which was made to move perfectly in
> sync with the standard PAL/NTSC vertical blank.
Yes, but in my experience this isn't terribly noticeable...
> >I find this whole interlacing business very annoying! Interlace was a
> >technical trick from the start of television to reduce the bandwidth
> >requirements - we really don't need it any more!
>
> Yeah legacy sucks :-)
Indeed!
--
Nick Craig-Wood
ncw1 at axis.demon.co.uk
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