How do I reinstall the video/camera drivers? FaceTime error message "no camera available/not connected.

My Mac Pro-Facetime camera has gone for lunch, error message "no camera is available/not connected", so as for the other device; Photo Booth,...etc. I believe the camera/video driver need to be reset by reinstalling the driver, but Apple does not provide any instructions or guidelines to do so or easily to reach that reset process. I think it is important every time when you somehow forced into up-dating your Mac, there are sometimes give you some headaches to report or correct the error(s) seeded inside the new updates. I figure, if the driver is there and camera not activated then there is a change that camera hardware might need to be replaced, but until you could check on the driver. I believe my Mac is fine and the camera is either been blocked by some malware or missing driver. Do you agree with above theory? Please anyone who could help, how to reinstall the driver.. really appreciated your input. Again thank you!