[kwlug-disc] Video of ARM PC build, with HDMI input (?) included

[Mikalai Birukou]

This is a video I just saw: https://www.youtube.com/watch?v=6C8QTf7GLfs

This is the board with RK3588: 
https://liliputing.com/radxa-rock-5-itx-is-now-available-itx-motherboard-with-rk3588-processor-and-lpddr5-memory/

I found interesting that it has hdmi input besides usual hdmi outputs. 
How can this be used? Is it like video capture?