[mythtv] Jerky video & prebuffering pause messages with MergedFB multi-screen setup

[Gee, David]

Hi,
 
I have a dual-head setup using the DVI and VGA outputs on my ATI Radeon
9200SE video card. Xorg is set up to use the "radeon" driver, and it uses
the driver's MergedFB option for the dual-headedness, because I understand
it's better than the generic Xorg multi-head capabilities (and also I
couldn't get the Xorg native stuff to work). Anyway, when I attempt to play
TV through Myth, it's very jerky (like 1 second of audio/video, then a few
seconds pause, etc.), and the console outputs the following stuff.
 
2006-06-05 18:58:21.037 TV: Changing from None to WatchingLiveTV
2006-06-05 18:58:21.058 Realtime priority would require SUID as root.
2006-06-05 18:58:21.133 Video timing method: DRM
2006-06-05 18:58:24.240 NVP: prebuffering pause
2006-06-05 18:58:27.329 NVP: prebuffering pause
2006-06-05 18:58:30.431 NVP: prebuffering pause
2006-06-05 18:58:31.032 New DB connection, total: 3
2006-06-05 18:58:31.041 Connected to database 'mythconverg' at
host:localhost
2006-06-05 18:58:31.961 rebuffering (7221 32768)
2006-06-05 18:58:32.101 rebuffering (19993 32768)
2006-06-05 18:58:33.629 NVP: prebuffering pause
2006-06-05 18:58:33.873 rebuffering (19901 32768)
2006-06-05 18:58:34.333 rebuffering (1549 32768)
2006-06-05 18:58:37.026 NVP: prebuffering pause
2006-06-05 18:58:40.123 NVP: prebuffering pause
2006-06-05 18:58:42.936 TV: Attempting to change from WatchingLiveTV to None
2006-06-05 18:58:43.230 TV: Changing from WatchingLiveTV to None
2006-06-05 18:58:43.242 Enable DPMS

I've tried disabling the realtime priority option, and running mythfrontend
as root so it can use the realtime threads, but I still see the same
problem. This never used to happen when I was running in single head mode
and I'm not quite sure what to do to fix it so I'd appreciate some
suggestions. I'm running the latest version of Myth and the ivtv drivers,
and I have a Hauppauge WinTV PVR 150 PAL TV card. I'm running the latest
stock Fedora 2.6.16 kernel.
 
Thanks in advance.
 
Regards
David Gee