Fix "no connected camera" error on your Mac

Errors with the VDCAssistant background process may prevent camera connectivity on your Mac.
Do you regularly use your Mac's iSight camera for chatting and other purposes, and have you run into a "no connected camera" error in the application you're using? If so, then a few causes and fixes are available that might help you out.
OS X Daily has recently outlined one cause and fix for such problem. When you run a program that uses your Mac's webcam, OS X will launch a background process called VDCAssistant, which manages the connection and control of the camera. While this process should quit when the program stops using the camera, it may persist if an error occurs, and prevent future connections to the camera, either by the same program or by others.

When the camera is unavailable, you will see a "no connected camera" error in programs and services that use it.

(Credit: Screenshot by Topher Kessler/CNET)

The fix in this case is to force-quit the VDCAssistant process, so relevant programs can again launch it normally and establish connections to the webcam. To do this, you will need to perform the following steps:

1. Quit the program using the camera.
2. Open Terminal and run the following command (supply your password when prompted, but remember it will not show)
   
   sudo killall VDCAssistant
   You can optionally open Activity Monitor to perform this step, by selecting "All Processes" from the View menu, then searching for and force-quiting the "VDCAssistant" process.
3. Now re-launch your program and try using the camera again.

In addition to the VDCAssistant process as the root cause for camera connectivity problems, other system configurations and problems may lead to similar behavior. For one, if you use a MacBook and have an external monitor attached, then one option is to use the system in "clamshell" mode where you keep the lid closed and only use the external monitor as a display. If you do this, then even though the built-in speakers and microphone will work, the camera will be shut off and unavailable to programs that need it. In this case, programs like Messages will allow audio chats, but not video options.
The next option is USB connectivity issues that may occur from incompatibility with third-party USB devices, or an error that may have occurred with the drivers in your system. This may happen if you use a third-party USB driver, or if the device itself is simply causing faults in your USB system. While poor coding may contribute to this, often its simply a temporary issue that can be fixed by turning off (and unplugging) third-party USB devices and then plugging them back in, or by restarting your Mac.
Alternatively, try unplugging all but the necessary USB devices (keyboard, mouse, etc.) from your system, restarting, and seeing if the problem continues. Troubleshooting in this manner can help identify a specific device that may be spurring the problem. If you do find the culprit, try leaving this device unplugged, updating its included drivers and other software, applying any firmware updates (if available), or contacting the manufacturer to see if a known solution is available. Sometimes such problems occur with the use of USB hubs and other daisy-chained solutions, so in addition to identifying specific devices, try changing the order in which they are connected to your system (bypass a USB hub, if used, or swap USB ports).
 Via