Measuring HDMI Video Latency
Video latency can be measured using a Leo Bodnar video signal lag tester for the following HDMI 2.0 (TMDS) video formats:
|3840x2160p 60.00Hz||1920x1080p 60.00Hz||1280x720p 60.00Hz|
|3840x2160p 50.00Hz||1920x1080p 50.00Hz||1280x720p 50.00Hz|
|3840x2160p 30.00Hz||1920x1080p 30.00Hz|
|3840x2160p 25.00Hz||1920x1080p 25.00Hz|
|3840x2160p 24.00Hz||1920x1080p 24.00Hz|
⚠️ 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:
- Record the reported lag value at the center of the middle white block.
- Use the following table to calculate the video latency based on the value recorded in step 1:
|24 Hz||subtract 20.0 ms from middle measurement|
|25 Hz||subtract 19.2 ms from middle measurement|
|30 Hz||subtract 16.4 ms from middle measurement|
|50 Hz||subtract 9.6 ms from middle measurement|
|60 Hz||subtract 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 750 lines, 1125 lines, and 2250 lines for 720p, 1080p, and 2160p respectively.1
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.
If you’re using the 4K tester, you can also update the firmware to the latest version provided by Leo Bodnar.
Last updated on March 15th, 2022.