I have not been able to get simultaneous video+audio capture to work on OSX. Under VLC 2.0.9, it had to be done via command line. Now with 2.1, the UI supports it. But, in both cases, this is the error generated:
main error: slave[0] doesn't like DEMUX_GET_TIME -> EOF
main debug: slave 0 EOF
To duplicate the issue, open VLC 2.1.1 on a MacBook Pro, select "Open Capture Device" and check the Facetime camera and built in microphone. I would expect to hear feedback as I tap on the laptop if Built-in microphone is the selected audio source. This brings up another issue... the Messages window is broken in 2.1.x. It is cut off in the middle of the window, so you can't see all of the messages. So, you have to close the capture window, and do the Open Capture Device a second time to see the error listed above.
On 2.0.9, I use this command line to open VLC:
open -a /Applications/VLC.app/Contents/MacOS/VLC --args -vvvv "qtcapture://" --qtcapture-width 640 --qtcapture-height 480 --input-slave="qtsound://"
It generates the same error. I can use that command line on 2.1.1 as well, but you can't see the error because of the Messages window bug.
This was suggested to be a code regression bug, but that was a long time ago...
https://forum.videolan.org/viewtopic.php?t=101126