[mythtv-users] Interlacing [was: Pvr250 issues - any suggestions?]

[Nick Craig-Wood]

On Sun, Apr 11, 2004 at 12:40:41PM +0200, Gert van der Knokke wrote:
> Nick Craig-Wood wrote:
> > Or alternatively why doesn't mythtv display interlaced video the way
> > it was intended to be displayed?
> >
> > Mythtv is currently displaying frames at 25 (PAL), 30 (NTSC) Hz which
> > look like this
>
> Yep, but your monitor isn't... Since most monitors  run at 70-100 Hz you 
> never get this right and you'll end up having the tearing effect during 
> motion...

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...

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.

One day if I get time I'll try this experiment!

> I mentioned this before on the list since this is the same problem with 
> 100 Hz TV-sets, if you have a chance to view some next to each other 
> then try to view a channel with a ticker line and you can immediately 
> see the difference between good and bad 100 Hz sets..

Yes an interesting point!  This isn't quite the same problem though,
but its close...

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!

-- 
Nick Craig-Wood
ncw1 at axis.demon.co.uk
http://www.axis.demon.co.uk/