[mythtv-users] deinterlacing and non-smooth playback at 1080i

[Seth Daniel]

On Mon, May 21, 2007 at 08:54:51PM +0100, Mark Kendall wrote:
> On 5/20/07, Seth Daniel <mythtv.org at sethdaniel.org> wrote:
> > On Sun, May 20, 2007 at 10:00:43AM +0200, Mario Minati wrote:
> > > Seth Daniel schrieb:
> > Good thought.  However, the nvidia driver doesn't handle sending 1080i
> > content to a 1080i resolution very well at all.  So you have to
> > deinterlace to have any hope of a decent picture (or such is my
> > understanding).
> >
> > http://www.nvnews.net/vbulletin/showthread.php?t=90959
> > http://www.nvnews.net/vbulletin/showthread.php?t=91471
> > (...and others...)
> 
> I'm fairly sure that deinterlacing 1080i content displayed at 1080i is
> just treating the symptoms and not the cause i.e. it gives you
> consistently 'mediocre' output quality rather than inconsistently
> good/bad quality.

You are absolutely correct in everything that you say.  However, AFAIK,
the only way to get good 1080i playback with 1080i content while using
an Nvidia card is to deinterlace.  It's not as if I haven't tried to
play the 1080i content w/o deinterlacing.  It's just that when I do play
the 1080i content w/o deinterlacing I get sync problems (see
http://www.nvnews.net/vbulletin/showthread.php?t=90959 for a little more
iformation).  I have tried playing 1080i @ 1080i with the various nvidia
sync options turned on, turned off, combinations of the two.  I have
tried using Myth's OpenGL sync turned on, turned off.  No matter what I
have tried to do to play 1080i content @ 1080i it always has the same
problem: every 15 seconds the sync is off, then it is correct for 15
seconds, then 15 seconds later it is off again, and so on.  


> For what it's worth, I'd try:-
> 
>  -  turning off deinterlacing. You're only complicating the issue.

Tried a million times.  I have never gotten it to work unfortunately.
I'm now convinced (after reading nvnews for the past few months) that it
is an nvidia bug.  The only way I know to work around the bug is to get
de-interlacing working.  As you have read, from my orginal e-mail, I
have issues with deinterlacing also.

>  -  force the video scan to interlaced in the on screen menu. You have
> a 1080i stream that contains frames reported as progressive which
> caused deinterlacing to alternate on and off - although turning off
> deinterlacing should resolve it anyway.

Yeah, the only reason it is reporting progressive frames is because I'm
deinterlacing.  When I turn off deinterlacing it doesn't do that
anymore, but then I get the sync issue.


> If all is well, you'll now have perfect playback.

I wish!  On my tv 1080i looks so much better than 720p (especially with
1080i material), but I have never had success with 1080i playback of
1080i content (all other interlaced and progressive material is fine).


> Does that describe what you're seeing? Best to test with a
> clip/channel with a news ticker moving from right to left.

I have tons of test material (lots of recordings of various shows that
are broadcast @ 1080i).  All exhibit the problem I describe in the first
paragraph above.

-- 
seth / @sethdaniel.org
I used to work in a fire hydrant factory.  You couldn't park anywhere near
the place.