I wonder if anybody tried to synchronize PIC to video signal. The problem is
(as far as I understand) interrupt latency. I am using 14.31818 MHz crystal
(k x horizontal sync frequency) and enable external interrupt by horizontal
sync pulse. Then I generate levels I need in a video line. I assume that due
to chosen crystal frequency interrupt latency should be equal for each line
in a field. Nevertheless vertical line on a screen have jitters of about one
cycle size (~280 nS). According to datasheet  (I am using 16C71) interrupt
latency = 3-4 cycles depending on where interrupt occurred during an
instruction cycle time. It looks like this +/- 1 cycle gives jitters
observed.
If anybody faced this problem and found the way around it, please let me
know.
Thank you in advance.

Gennady Palitsky
Jefferson Audio Video Systems
gennadyp@mainlink.net