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Using the LM1881 to detect the start of a new video frame

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TimB100:

Hi every one, sorry this may be obvious to others but its not for me.

I'm working on a project that will use the LM1881 sync separator. One of the tasks I need to do is count the horizontal lines to know what line I'm on.
There is a signal generated for every H scan which is great but the Vsync line is not at the start of the first H line. Its in the middle of a load of other Hsync pulses.
I'm going to be using a Pic to do some analysis of the video signal so can obviously do some timing. Perhaps after the Vsync count the Hsync pulses to get to the first Hsync of the new frame scan. Or time it for x us then wait for the next Hsync and that will be the start of the first line etc etc.

Its obviously not rocket science as even a 12mhz pic can generate text overlays in the same place every time.

Can anyone tell me the best method?

Many thanks

Tim

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