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.
http://www.cs.yorku.ca/~av/Genlock.htm
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
************************************************************************* * Cory Papenfuss * * Electrical Engineering candidate Ph.D. graduate student * * Virginia Polytechnic Institute and State University * *************************************************************************
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