It’s “face detection blocking” built into the camera/display. Otherwise, the video footage is just straight sent as ONVIF to the main DVR for whatever processing is done there (which could be a lot more nefarious).

Wren Solutions / Costar seem to be the main vendors of these “public view monitors” — such as the PVM10-B-2086.

https://6473609.fs1.hubspotusercontent-na1.net/hubfs/6473609...

“Face Detection Boxes (Neon Green, Front and Side Detection)”