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

[Steve Smith]

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
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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
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