QuickTime Player.app New Movie Recording Error: won't record How do I get rid of this error icon and use QuickTime Player to record from my FaceTime HD Camera?



The FaceTime HD Camera is listed as one of the input options:



The New Audio Recording and New Screen Recording features work, but not the New Movie Recording (which uses the FaceTime HD Camera as an input).

QuickTime Player Version 10.4 (894.1)
macOS Sierra 10.12.3 (recently upgraded from 10.12.2, prior OSX Lion factory install)
late-2012 AirBook (i7, 2GHz, 8GB RAM, 400+GB free internal SSD available)
I don't know why this was a problem in the first place, but I was able to resolve the issue from the Activity Monitor so that QuickTime can now access my FaceTime HD Camera:


launch Activity Monitor
select Activity Monitor >> View::All Processes
select the process "VDCAssistant"  (owned by root)
select Activity Monitor >> View::Quit Process
 (also: Option+Cmd+q)


The same can be done from the command line with killall:
sudo killall VDCAssistant

...and here's a more complete listing of things to try if the FaceTime camera has gone wonky.