[mythtv-users] Viktor's Bob deint patch for interlaced modelines

Tom Dexter digitalaudiorock at gmail.com
Tue Jan 29 22:15:02 UTC 2008


On Jan 28, 2008 10:01 AM, Steve Smith <st3v3.sm1th at gmail.com> wrote:
>
>
>
>
> On 28/01/2008, Tom Dexter <digitalaudiorock at gmail.com> wrote:
> >
> >
> >
> > On Jan 28, 2008 8:24 AM, Mark Kendall <mark.kendall at gmail.com> wrote:
> > > On 28/01/2008, Steve Smith <st3v3.sm1th at gmail.com> wrote:
> > >
> > > The code will/should only reject display modes where it believes the
> > > display refresh rate (50Hz ideally) cannot support doubling the source
> > > frame rate ie. from 25Hz to 50Hz.
> > >
> >
> > With interlaced modelines, myth reports 60Hz REFRESH rates at 30 and
> > 50Hz and 25, thus disallowing use of Bob.  I've been confused by that
> > for some time:
> >
> > http://www.gossamer-threads.com/lists/mythtv/dev/302387
> >
> > That's what the patch originally posted by Viktor is for.  I can't use
> > Bob (which looks awesome on my TV by the way) without it.
> >
> > Tom
> >
> > _______________________________________________
> > mythtv-users mailing list
> > mythtv-users at mythtv.org
> > http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
> >
>
> Tom,
>
>
> Actually that's not quite the problem. REFRESH refers to the FRAME rate
> which for normal TV sources is going to be:
>
> NTSC: 30Hz (approx)
> PAL: 25Hz
>
> When you see 60Hz and 50Hz that refers to the FIELD rate, as each FRAME is
> composed of TWO FIELDS whose lines are INTERLACED to produce the final
> FRAME. The problem for progressive displays is that the two fields are not
> actually part of the same picture, they are of two different points in time,
> which is where the combing artifacts come from.
>
> Whilst Viktor's patch works, it actually needs to be applied to the bobdeint
> code to detect the interlaced ouput mode and allow the 25/30hz refresh,
> rather than artificially telling all of myth that the refresh rate is 2x
> what it actually is.
>
> On the other hand it does work! and very well!
>
> What I'd really like to see is a specific INTERLACED OUTPUT mode/profile for
> Myth which is basically the same as bobdeint running at field rate (i.e.
> 50/60hz), for use when the display device is interlaced i.e. standard CRT
> TV, 1080i etc
> (personally I think all this kernel deinterlace etc stuff is a bit of a
> waste if you can actually display interlaced signals natively!)
>
> Cheers
>
> Steve
>
>
Thanks for the explanation...that makes more sense.

I really do wish nVidia would just get the interlaced output right in
their drivers and make the whole issue go away.  At this point, seeing
how many people have griped to them about it and the fact that they've
never even acknowledged that there's a problem, I'm pretty sure they
plan on just riding it out until all there simply aren't any CRT
displays left out there.

By the way...do you know offhand if that patch still works in trunk?
If there's no better alternative when 0.21 comes out I'd still like to
use it.

Tom


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