Video
Tri-Level Sync
01 — Definition
The HD reference synchronisation signal used for genlock, replacing SD's black burst. It is a three-level bipolar pulse (positive, zero, negative) that resists timing errors better than two-level SD sync. It is distributed from a sync pulse generator to every camera, switcher and capture device, and its frame rate must match the video format (1080i50 sync for a 1080i50 show).
02 — In the field
Feed a camera a 25 Hz tri-level reference on a 29.97 fps show and nothing will lock: the reference rate has to match the project rate exactly. Check that the sync generator's format matches the show format before you cable the cameras.