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

Steve Smith st3v3.sm1th at gmail.com
Tue Jan 22 14:36:35 UTC 2008

On 22/01/2008, Christopher Friend <christopher_friend at hotmail.com> wrote:
> Hi, does anyone know of a mythtv package for Ubuntu that has Viktor's bob
> patch compiled in? Or has it been included in the main mythtv branch
> already? There was some talk about a mythtv-vid branch but I think that was
> merged a while ago, though with or without the patch I've no idea...
> I've just tried a VGA to scart cable with a 720*576 PAL interlaced
> modeline and am coming up against the same sync issues that others seem to
> have; unless it's paused and started again at a specific frame it has either
> constantly jerky movement or slight jerks every few seconds, usually
> starting when there's a lot of movement on screen. Currently if I use bob
> it seems to drop to about 1 or 2 fps so is unusable. Other deint methods are
> ok but not as smooth as interlaced when it's working.
> I'm also getting slight flicker to any still images outside of tv watching
> (desktop, myth settings etc), more so than via a regular tv image (via dvd /
> stb / analogue). Using a progressive 50Hz modeline looks alright so I don't
> know if it's something to do with the interlaced modeline or something
> else...
> Does anyone have any recommended PAL interlaced modelines? Preferably
> standard 720*576 or 768*576? I've tried a few (mainly from steve hall's
> nexus page and a gentoo mythtv wiki) but get varying results with them
> (some are more likely to jerk during tv playback than others) so I wanna try
> out as many as possible.
> Thanks, Christopher
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> Chris,

I've been trying to figure this out myself as I currently use Viktor's patch
on my 0.20 system.
Looking at the source code for mythtv-vid and the current trunk, it seems
that it might be in for OpenGL mode but not normal XvMC mode, so you'll
still have to do the modification yourself....

However, your experience with bob sounds a bit odd. What should happen if
you try to use bob with an interlaced modeline it should complain about the
refresh rate being too low and drop back to "onefield" (check this using
"mythfrontend -v playback"). I wouldn't expect it to drop to 1-2fps unless
you were very CPU bound!

It's probably something to do with your sync settings, have a play with
Also are you trying to watch DVB-T (Freeview) recordings with XvMC enabled?
(Do a search for some of my postings related to this if you are...)


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