Genlock Sync

The Heartbeat of the Set

Genlock, short for Generator Lock, is an essential synchronization technique in any multi-camera or complex video environment, and it is absolutely critical for In-Camera VFX (ICVFX). The core function of a genlock signal is to act as a master ‘heartbeat’ for all video-related equipment. It forces every device—including all cameras, computer render nodes, and the LED wall itself—to start and end their video scanning process (the drawing of each frame) at the exact same instant.

Preventing the Rolling Shutter Bar

On an LED wall, the individual LEDs are refreshed line by line, from top to bottom, very rapidly. A film camera also captures its image by scanning, either with a mechanical or electronic shutter. If these two scanning processes are not perfectly synchronized, the camera’s shutter might capture the LED wall while it is in the middle of a refresh cycle. This results in a prominent and distracting visual artifact—typically a dark horizontal bar or banding that appears to roll through the image on the LED screen.

By using a master sync generator to send a genlock signal to every piece of equipment, the production ensures that the camera’s shutter is only ever open when the LED wall is displaying a complete, stable image. This perfect timing alignment is fundamental to creating a clean and usable final pixel image in an ICVFX workflow.