What is Genlock?
Genlock (Generator Lock) is a hardware signal that forces a camera's internal sync generator to lock its phase to an external reference — either Blackburst (SD) or Tri-Level Sync (HD). When genlocked, all cameras begin their sensor exposure at the exact same microsecond. This eliminates the phase offset that causes frame tearing when cutting between cameras in a live switcher.
Without genlock in a live multi-camera setup, each camera's sensor fires at a slightly different time. On an ATEM or vMix, an instant cut between two cameras will show a momentary horizontal tear — or require a frame synchronizer (adding ~1 frame of latency) to hide it.
What is SMPTE Timecode?
SMPTE Timecode is a metadata standard that stamps each video frame with a unique address: hours, minutes, seconds, and frames (HH:MM:SS:FF). It has nothing to do with when the sensor fires — it only identifies what the frame is called. Linear Timecode (LTC) is embedded in audio channels; Vertical Interval Timecode (VITC) is embedded in the video signal itself.
Timecode is essential for post-production: it lets NLEs like Premiere Pro and DaVinci Resolve automatically sync multi-camera footage. But two cameras can have perfectly matching timecode and still be completely out of phase at the sensor level — causing the flicker problem on LED volumes that timecode alone cannot fix.
Why Both Matter for XR & LED Volumes
In XR (Extended Reality) productions using LED volumes with Unreal Engine, genlock is non-negotiable. The camera must be genlocked to the LED wall's refresh cycle to prevent the camera from capturing partial frames of the LED content — a visible horizontal banding artifact. Read the full technical guide →
PTP (Precision Time Protocol) is increasingly used in IP-based broadcast facilities to replace analog genlock signals, providing sub-microsecond synchronization over standard Ethernet — compatible with SMPTE 2110 workflows.
Frequently Asked Questions
What is the difference between genlock and timecode?
Genlock is a hardware synchronization signal that aligns the physical timing of camera sensors so they all expose frames at the same moment. Timecode is a metadata label that identifies each frame with a timestamp address. You can have one without the other — but broadcast studios need both.
Can timecode replace genlock?
No. Timecode tells you which frame it is. Genlock controls when the sensor fires. Two cameras with identical timecode can still be completely out of phase, causing visible tearing on live cuts or LED flicker in XR setups. They solve different problems.
What is Tri-Level Sync (TLS)?
Tri-Level Sync is the HD version of Blackburst. It's the reference signal distributed across a studio that cameras lock to for genlock. The signal has three voltage levels (hence "tri-level") and runs at the production frame rate. Most professional broadcast cameras and switchers support Tri-Level Sync input via BNC.
Do I need genlock for an NDI or IP video workflow?
For pure NDI workflows, frame synchronizers in the software handle the timing differences. However for IP workflows following SMPTE ST 2110, PTP (IEEE 1588) replaces analog genlock signals by providing sub-microsecond timing synchronization over standard Ethernet — delivering the same phase-lock result without physical sync cables.