Taking a snapshot from a non-standard ONVIF implementation/

I have a CCTV camera that only partially support the ONVIF standard.

I can control most of the functions through Home Assistant, but I can’t take a snapshot using the normal snapshot function. The option simply isn’t presented to me when I try to create a new automation.

I can play a video stream without any problems. Is there any way to automatically capture a still from this?

Is there any way to interrogate the ONVIF configuration directly to see if it has a hidden snapshot function, I’ve previously seen phone apps that can pull a config off of a camera.