From time to time, with some older versions of Skype or other video apps or even in some unexplained cases with OS X El Capitan, the FaceTime (front facing) camera can fail to work with the message "There is no connected camera." Here's a quick tip on how to bring the camera back to life.
Background. Occasionally for some reason, an app that uses the FaceTime camera may fail to properly close a system process that manages it. There has even been a report of this happening in OS X El Capitan for no apparent reason. There are several ways to do this, in increasing order of complexity.
1. Easy. Reboot the Mac. That will reinitiate all processes that were running but not properly exited. However, that may be inconvenient under some conditions.
2. Moderate. Quit any apps that may be using the camera. From the /Applications/Utilities folder, launch the Activity Monitor.app. Click the top of the left column where is says "Process Name" to cast the list into alphabetical order, and then look for the process "VDC Assistant" in the list below. Select it, then click the "x" icon on the extreme top left to kill the process. You'll get a confirmation dialog like this.
Relaunch the app you need that uses the camera.
3. Geeky. This involves a simple terminal command and isn't hard to do. First, quit any apps that might be using the camera. Then open the OS X Terminal.app (Also found in /Applications/Utilities). Enter the following command.
sudo killall VDCAssistant
It looks like this:
This process is owned by root as it interfaces to the hardware. So the string 'sudo" is required at the start. (Here's more info on the sudo command.) You must be an admin user, and then enter your admin password. (Just type it; you won't get visual feedback.)
The next time you launch an app that uses the FaceTime camera, everything should be fixed. As they say.