> I am using PIC microcontroller (4 MHz crystal) and LM1881 to add a white
> box to
> composite video at a specific location on TV. The problem i am having
> is that the box is not stable and moves on TV horizontally.

That means you have some jitter in your response time for starting the white
box signal.  With a 4MHz PIC the response will have 1uS jitter at best
unless the clock is somehow synced to the vide.  The jitter could be much
more depending on how you are trapping the signal and getting the PIC to do
whatever it is supposed to do.  I don't think a PIC (or most any
microcontroller) is a good choice for generating video that is externally
synced without some special sync circuitry.  It would be a lot easier if the
micro could generate the sync itself.


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