[moved] trigger signal for video line

[betwixt]

to reset counter what should be the state of Vout?

That depends on what type of couter you choose. The falling edge would be my choice.

how i can find the beginning of the video frame using VOUT?

The Vout signal falls at the begining of each field. The odd/even signal changes once per field. A frame is two interlaced fields. If you assume the odd field is the one with line 1 in it, you use the falling Vout signal at the same time odd/even is high.

Brian.