Version: many, currently 50.0.2661.94
OS: Mac OSX, currently 10.11.4

What steps will reproduce the problem?
(1) Enter a Google Hangout or other VC app within Chrome
(2) Video and audio output work, but input via headset or built-in microphone fails (other attendees/call recipients hear no audio)

This problem has been occurring for me and others in Hangouts meetings intermittently for several months.. on canary and stable.  I have even had the mic input work, go out, come back, and go out again within the same session.  It seems to be limited to Chrome on OSX and not specific to Hangouts, some notes from my occurrence yesterday:
- Mac system audio config and testing of the mic show it working properly
- Switching to another browser and entering the Hangout, the mic works
- Switching tabs/profiles/launching a new Chrome window still fails
- Switching audio devices, turning mute on/off the mic still fails
- Other audio input tests within Chrome fail, ie https://test.webrtc.org/? reports this audio capture failure, with headset or default device:
[ FAILED ] No active input channels detected. Microphone is most likely muted or broken, please check if muted in the sound settings or physically on the device. Then rerun the test.

I am happy to help troubleshoot further and have left my laptop/Chrome in the failed state (if it continues).

May be related to or potential duplicate of chromium:504363, though some users there report different behavior, namely successful tests outside of Hangouts/Gmail.