[mythtv-users] New deinterlacer for perfect image quality when using an interlaced display, mode that matches the source

[Tom Dexter]

On Fri, Apr 10, 2009 at 6:50 AM, Paul Gardiner <lists at glidos.net> wrote:
> Tom Dexter wrote:
>>
>> An update on my ongoing testing.  Since it takes me over an hour to
>> compile, and the fact that I can't do it during evening TV watching
>> time :D, I'm a little limited as to when i can do this sort of stuff.
>>
>> First of all, I noticed the same motion issues with my recording of
>> Law and Order: SVU from Tuesday...so I have more content to test with.
>>
>> This morning I compiled with your original patch (the one without the
>> OSD flicker fix).  Believe it or not, both shows look fine with
>> that...no problems at all.  I even watched a good portion of Medium
>> over again to make sure.
>
> That's good news. If nothing else, at least this means you have a
> solution. It also has to be very useful information for getting
> to understand the problem.
>
>> Tomorrow morning I'm going to try again with the version of the
>> original patch that has to OSD flicker fix just to see if for some
>> reason that's related.
>
> Yeah, that would be a good test. I'd expect the problem to return
> with that patch because, as far as I can tell, it does the same job
> as Mark's verion. If the problem does return, one more change worth
> trying is to change - in function "filter_func" - the inner condition
> from
>
> ((y ^ tff) & 1) == 0
>
> to
>
> y & tff
>
>
> The no-flicker patch actually has two alterations, one to remove the
> flicker and the other to deal with bottom-field-first content. The
> change I suggest above will retain the flicker fix, but revert the
> bottom-field-first fix.
>

Yup...it looks as though the bottom-field-first fix is causing it.

My first test today was using the version of the original patch with
both the OSD flicker and bottom-field-first fixes.  The problem was
there for sure.  One of the clear signs of this issue shows up not
necessarily with significant motion (the kind where you'd notice
tearing), but for example, with people talking...not an audio/video
sync problem, but rather an almost animated look when people are
talking...extremely unnerving and unnatural looking when it happens.

However with the bottom-field-first fix removed as per your above
change, everything's fine.

So it appears that that fix, in conjunction with some 1080i content
that has progressive frames mixed in (NBC stuff specifically) is
causing this.

Interestingly though, I've yet to have any similar problems with CBS
shows, and they tend to do the same...though possibly less.  One
difference between NBC dramas and CBS though is that NBC also uses
different frame rates for commercials.  That's what causes the issue
where the OSD will show a one hour show was, say, 51 minutes...because
myth is assuming a constant frame rate when calculating the length.  I
wonder if that's in any way related.

Tom