Video Latency Timer
A high-resolution timer for measuring end-to-end video link latency ("glass-to-glass") — from an event in front of the camera to the picture in your goggles or on the ground station screen.
How to measure latency
- Open this page on a monitor or laptop — the timer starts automatically. The Fullscreen button removes everything else from the frame.
- Point the drone camera at the screen so the digits fill most of the frame and are in focus.
- Place the ground station screen (or goggles with an external display) next to the monitor so both images are visible at once.
- Photograph both screens in a single shot — with a phone at a short exposure.
- Subtract the number on the ground station screen from the number on the monitor — the difference is the latency in milliseconds.
- Repeat 5–10 times and average the results: a single shot may land in different phases of the screens' refresh cycles.
Measurement accuracy
The digits update at your display's refresh rate: at 60 Hz that is every ~16.7 ms, so a single measurement carries up to one frame of error on each side. A 120/144 Hz monitor cuts that in half or better — the fps counter on the timer shows the actual rate. The frame counter next to the milliseconds gives a cross-check: frame difference × ms/frame ≈ latency.
Common mistakes
- Long exposure — the digits smear across two frames. Shoot at 1/500 s or faster (use your phone's Pro mode).
- Browser throttling fps — laptop power-saving modes can cap the frame rate. Verify the fps counter matches your display's refresh rate.
- Measuring from a video recording — the recording has its own frame rate and adds uncertainty. Use photos.
What affects latency
End-to-end latency is the sum of: camera sensor exposure and ISP, encoding (bitrate and codec settings), the radio link (WFB-NG, FEC buffers), ground station decoding and display output. If your result is too high, start with bitrate settings and Adaptive-Link.