Tri-level sync

Tri Level Sync is an analogue video sync pulse primarily used for the locking of HD video signals. Genlock

It is preferred in HD environments over black and burst as timing jitter is reduced due to the nature of its higher frequency. It also benefits from having no DC content as the pulses are in both polarities.

Waveform

The main pulse definition is as follows, a negative going pulse of 300mv lasting 40 sample clocks followed by a positive going pulse of 300mv lasting 40 sample clocks. The allowed rise/fall time for each of the transitions is 4 sample clocks. This is with a clock rate of 74.25Mhz