[mythtv-users] Bob deinterlace and Xv problems

[Steven Adeff]

On 5/12/06, Tom Lichti <tom at redpepperracing.com> wrote:
> Doug Larrick wrote:
> > Dan Seddon wrote:
> >> When I choose to use bob deinterlace without XvMC, meaning it must be
> >> using Xv, everything starts off fine then after a short while X starts
> >> to climb in it's processor usage until it's using all that remains after
> >> myth (about %65). It took me a while to catch on to this (it causes
> >> stuttering which after months of trying to get rid of XvMC I wasn't
> >> looking in the right place), it was only when I logged in from my laptop
> >> and did a top that I saw what was going in. Turning off bob-deinterlace
> >> solves the problem - which is bad as you really need bob when displaying
> >> on a montior as I am. I'm sure it's not a processing limitation as in
> >> the worse case all that can be happening is that Xv is splitting the
> >> fields and doubling up the frames on the fly, before scaling up? So, it
> >> has four times the scaling to do - but that shouldn't be an issue to an
> >> Nvidia card. Has anyone seen this and, even better, know how to prevent it?
> >>
> >
> > Besides the processing you mention, bob also doubles the effective
> > output framerate, and so doubles the overhead of the video output thread.
> >
> > If "Onefield" deinterlacing (which does the same processing but doesn't
> > double the framerate) causes similar issues the problem is elsewhere,
> > but if not I'd suspect you're on the hairy edge of required processor power.
> >
> > Also make sure you're using a good video sync method (look at
> > 'mythfrontend --verbose playback').  OpenGL vsync is good, so long as
> > your nVidia driver is not the (79xx? 81xx?) version that sucks down a
> > ton of CPU time if you turn that option on.
> >
> > -Doug
> >
> I was experimenting with de-interlacing/xvmc last night, and found
> something interesting. First off, I am using the mythtv-vid branch, with
> an nVidia 6200 AGP card and a P4 2.93 processor displaying SD video from
> PVRx50 cards, with the latest nVidia drivers (8756). What I found was no
> combination of xvmc/non-xvmc/de-interlacing methods worked acceptably
> (always got prebuffer pauses or buffer underruns) UNTIL I turned off
> OpenGL sync in the frontend settings. After I did that, bob de-interlace
> with XvMC works great, with the very occasional prebuffer pause (1 every
> 5 minutes?) and a very watchable picture. With OpenGL sync on, every
> combination I tried had prebuffer pauses every second or so, which
> effectively makes watching anything not very enjoyable. Not sure what
> all that tells us, but I'm happy.

I found this as well but with 0.19-fixes. I have OpenGL sync off and
use nvdia-setting's Xv Sync. I've got a 5200 and am runing 8756. I
also had OpenGL issues with 7676, but that had more to do with not
being able to even get it to work.

-- 
Steve
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