"No connected camera" error using MacBook Air

I have a friend with a 13" MacBook Air. He upgraded to the new software in the App Store about a week ago and now, when he is using anything that uses his built-in camera, it says "There is no connected camera." I've tried looking through his settings and nothing is working to fix the problem. I've found a number of problems, but nothing has worked. We're not sure how to go about solving the problem, even after finding several solutions to no avail. Anything helps, thanks!

Solution 1:

Probably there is some process holding the camera. A dirty hack to solve this issue is to kill the culprit with:

sudo killall VDCAssistant