Measuring Video Latency

Before measuring video latency, you should have a basic understanding of the difference between video latency and input lag.

Using the Leo Bodnar Tester

Video latency can be measured using a Leo Bodnar video signal lag tester for the following HDMI video formats:

3840x2160p 60.00Hz1920x1080p 60.00Hz1280x720p 60.00Hz
3840x2160p 50.00Hz1920x1080p 50.00Hz1280x720p 50.00Hz
3840x2160p 30.00Hz1920x1080p 30.00Hz
3840x2160p 25.00Hz1920x1080p 25.00Hz
3840x2160p 24.00Hz1920x1080p 24.00Hz

Steps

The Leo Boardnar testers are designed to report a display’s input lag when measuring at the center of the screen. Follow these steps to measure video latency instead:

  1. If you’re using the 4K tester, make sure that its firmware is up to date.
  2. Follow the setup instructions and usage guidelines provided by Leo Bodnar.
  3. Record the reported lag value at the center of the middle white block.
  4. Use the following table to calculate the video latency based on the value recorded in step 3:
Refresh RateCalculation
24 Hzsubtract 20.5 ms from middle measurement
25 Hzsubtract 19.7 ms from middle measurement
30 Hzsubtract 16.4 ms from middle measurement
50 Hzsubtract 9.7 ms from middle measurement
60 Hzsubtract 8.0 ms from middle measurement

The Leo Bodnar testers report the time between when the first active pixel leaves the FPGA and when its sensor detects the display has reached approximately 6% of full luminance. The tester outputs an HDMI signal with CEA timings.

Some earlier firmware versions of the fixed-resolution testers measured from the start of blanking rather than the first pixel. This was changed with later versions of the firmware to match the behaviour described in the previous paragraph.

Last updated on October 10th, 2021.