Black screen when camera is on and camera turns off after a few seconds.

Hi,

My facetime started showing a black screen instead of the camera output a few days ago and hasn't been fixed yet automatically.

When I'm on a call with someone and I check the camera on, they can see my face while I still see that blank screen and after a few seconds camera will turn off, and neither the peer can see me anymore.

I tried restarting and off/on my Macbook, but no luck.

I checked privacy settings, facetime is not on the list.

Any assistance would be much appreciated.