[mythtv-users] HDTV tearing solved

[Yeechang Lee]

I've previously reported here a tearing in the top 1/6 to 1/8 of the
picture on my 1080p panel with an Nvidia GeForce 6200 TC, the 7676
drivers, and MythTV 0.18.1 (see
<URL:http://www.gossamer-threads.com/lists/mythtv/users/173841> for
more info). I am happy to report that I've solved the issue.

I'd always had Sync to VBlank for OpenGL enabled in both
nvidia-settings and in mythfrontend. (By the way, loading the glx
module in xorg.conf or XF86Config is required for OpenGL sync to work;
the *only* reliable way of seeing whether mythfrontend is actually
using it is to check mythfrontend's log output, so start it from an
xterm. If it says RTC, it's not using OpenGL.) However, that never
helped with the tearing as far as I could see.

After seeing a recent message by Jarod Wilson regarding his
.nvidia-settings-rc, I tried *also* turning Sync to VBlank under 'X
Server XVideo Settings' in nvidia-settings. (I'd always kept it off
after, I think, having read someplace that I was supposed to.) This
got rid of the tearing, but the picture now flickered as if it was
skipping every other frame. I now tried switching the deinterlace
settings in mythfrontend from 'Kernel' to 'Bob,' which of course
offers twice the framerate. That did it; I now have a tear-free and
pretty much rock-solid playback. I now give MythTV's output a grade of
99% instead of 95% as before; not 100% because there still
*occasionally* seems to be some flickering, but it's so minor that it
could very well be my hypochondriac imagination.

I only wish I'd figured this out before ordering a used PCX 5300,
which arrived today. That said, I only paid $45 including shipping and
it's entirely possible that it will live up to my reason for buying
it, namely to give me such smooth playback (or perhaps even better)
without having to take the above extra steps.

-- 
Yeechang Lee <ylee at pobox.com> | +1 650 776 7763 | San Francisco CA US