[mythtv-users] xbox + xbv framerate solution

Dennis Cartier pvr at trigger.net
Sat Jan 10 11:19:50 EST 2004

Derek Watson wrote:
> Dennis, this may be of interest to you...
> I was recently alerted to a post in the gentoox forums that was talking 
> about framerate problems with mythtv in gentoox 
> (http://forums.shallax.com/viewtopic.php?t=378&highlight=mythtv). The 
> problem of course was the use of xbv, but someone there indicated that 
> the problem is with xv and some nvidia chipsets.
> The solution it turns out is to disabled double buffering using xvattr:
> xvattr -a XV_DOUBLE_BUFFER -v 0
> I've confirmed that this works. While watching tv at a low framerate and 
> running this in another shell, the framerate instantly comes back to 
> 25fps. The only problem I can see with this now is that occasional 
> tearing in the picture is visible.
> So the problem is very unlikely to be with xbv as such, but more likely 
> a quirk with xv and the state that it thinks the encoder is in. Maybe 
> vertical retrace is taking a long time (or xv thinks it is) so doesn't 
> flip the buffer as often as it should. I don't know anything about xv, 
> but maybe someone with experience with it could give us a starting point 
> on addressing the actual problem?
> Anyway, it's certainly a passable solution to the overscan problem. :-D
> Derek.

Thanks Derek. I will check this out. Between this and the directfb route 
it looks like the overscan issue will be a thing of the past. Yeah!


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