Genlock for LED Walls: How to Avoid Flicker and Lost Sync

Hampus Niskala |27/10, 2026

When a camera films an LED screen, the screen and the camera need to refresh in step. Otherwise you get rolling bands, flicker and tearing on camera, even when the screen looks perfect to the eye. Genlock solves this by locking the LED controller to the same reference signal as the cameras. This guide covers how to wire it and, just as important, the power and cabling mistakes that make Genlock fail on site.

What Genlock does

A sync generator sends a reference signal. The cameras, the video system and the LED controller all lock to it, so every frame starts at the same moment everywhere. On NovaStar COEX controllers, Genlock is available on every model except the KU20, and it's the basis for the camera features used in broadcast and xR, such as frame multiplication and Shutter Fit on the MX40 Pro, MX2000 Pro and MX6000 Pro. The NovaPro UHD Jr supports Genlock too.

Three ways to connect it

Star: the sync generator feeds each controller directly. The most robust option.
Loop: the generator feeds the first controller, which passes the signal on through its Genlock loop output to the next.
Cascaded generators: on big sites, one master generator feeds other generators, which then feed the controllers.

Use good-quality, double-shielded cable for the reference signal, the same quality you would use for 12G-SDI.

The most common cause of problems: power

NovaStar's own troubleshooting advice starts with power: many Genlock problems on site come from the power supply, not from the settings.

Give the sync generator its own clean power. Don't share a circuit with media servers, LED screens, lighting or sound systems.
On complex sites, give the LED controllers their own supply too, separate from high-power equipment.
If the mains is unstable, add a UPS or isolation transformer in front of the generator and controllers, sized for both.

Symptoms and what usually causes them

Symptom	Likely cause
Sync generator output flickers or drops out	Noise on the power line it shares with high-power equipment
Downstream generators won't lock	An unstable master generator in a cascade
Several controllers lose Genlock at once	Interference travelling along the Genlock cables, often from poor shielding
Problems appear as more gear is switched on	Too much load on a shared circuit

Checklist before the shoot

Separate, clean power for the sync generator (and for the controllers on bigger sites).
Double-shielded reference cables, as short as practical.
A star layout where you can; loops and cascades only where you have to.
Check every controller shows a locked Genlock status in VMP before cameras roll.

Choosing a controller for camera work? Our NovaStar COEX buyer's guide compares the camera features of each model.

Pixel Pitchers ships NovaStar from Sweden: order in-stock items by 14:00 CET for same-day UPS Express, with delivery in 1–2 days across the EU and no import duties.

Source: NovaStar COEX Wiki, Genlock.