[mythtv-users] How I got great quality TV-out on my nVidia MX4000

Cory Papenfuss papenfuss at juneau.me.vt.edu
Thu Mar 10 12:47:04 UTC 2005

> What about RTLinux or RTAI Linux? This would give the realtime performance 
> needed to respond to a VBI interrupt, the problem would be that the RTLinux 
> code to interract with the graphics card would have to be written from 
> scratch. Just a thought, I haven't really been following this thread.
 	I ran across this... looks interesting.


 	I've talked myself right out of genlocking with my previous post, 
however.  Genlocking is a *hard* realtime requirement, whereas since the 
PVR is fundamentally a timeshifting device, it's more of a *soft* realtime 
device.  That's not to say it's not interesting or a possible solution, 
it's just that it might be overkill.  The easiest way to adjust the time 
and keep everything synchronous would be to adjust the dotclock on the VGA 
card a very small amount.  That would keep the modeline timings the same 
on a per-frame basis, but adjust the actual time.

 	Of course, this is all dependent on the specific video card used, 
how adjustable it is, and some notion of a "reference clock."  See 
previous posts on linux not being realtime... :)


* Cory Papenfuss                                                        *
* Electrical Engineering candidate Ph.D. graduate student               *
* Virginia Polytechnic Institute and State University                   *

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