[mythtv-users] Jerky panning all cards and resolutions. Thoughts on where to look?

Ben Lancaster lists at benlancaster.co.uk
Tue May 15 08:27:32 UTC 2007

> Since day one I have noticed that panning scenes have a distinct 
> "gallop". This is independent of video mode, resolution, signal source, 
> real time setting or rendering method. On about a 1/2 to 1 second cycle 
> the pan will speed up and slow down in a repeating pattern. Nothing I 
> have tried has fixed the problem. I dont think this is related to cpu 
> usage as it happens even when playing SD which results in an average 
> usage of about 12%. HD playback is 50-55% usage. The box is a dedicated 
> myth system with a 2.8GHz AthlonXP mobile with plenty of memory. Signal 
> sources are 2 pvr-250's and a HDHR. Video card is a NVidia FX5200 using 
> the standard VGA output to drive my HD monitor. This has happened since 
> myth 0.19 and is present in 0.20, 0.20.1 and SVN so I doubt its myth 
> itself. Any suggestions on what else to check?
Are you by any chance watching 50Hz/25Hz source over 60Hz VGA? If you're 
in the UK/Australia then this is probably the case - the problem is 
caused by mythtv's framerate interpolation (adding the extra 10 frames 
to make it up to 60) as it would seem it just duplicates frames, hence 
the jerkiness

The only solution is to go for DVI->HDMI and set it to 50Hz. I tried 
component on my Nvidia 6200 card, but from what I read Nvidia have 
"locked" the component output to 60Hz, so you get the same problem.

Very annoying, I know. This is one thing that MCE has over MythTV - 50Hz 
video plays flawlessly smooth over a 60Hz link!


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