NotReadableError: Failed to allocate audiosource in Firefox for getUserMedia - firefox

Question

Running the below snippet in my Firefox console returns the following error [FF/56.0.2 (64-bit) on Mac OS 10.13.1]:
MediaStreamError { name: "NotReadableError", message: "Failed to
allocate audiosource", constraint: "", stack: "" } (unknown)
// Sippet
navigator.mediaDevices
.getUserMedia({
audio: true,
video: true
})
.then(stream=>{
console.log(stream.getAudioTracks())
document.getElementById('storybook-preview-iframe').contentWindow.document.getElementById('video-camera').srcObject = stream
mr = new window.MediaRecorder(stream, {
mimeType: 'video/webm'
})
mr.ondataavailable = console.log
})
.catch(console.log)
What is most troubling is it worked at one point, and then it stopped. As if something is permanently locked up... I have no way (as far as I can tell) to see what is wrong with the audio source.
I ran these insanity checks to no avail:
No other browsers or app were open and/or using camera
Restarted browser, and eventually restarted computer
I'm on a mac, and heard this would help #> sudo killall AppleCameraAssistant;sudo killall VDCAssistant. It did not.
Ran a separate script (https://jsfiddle.net/App7P/348/) but when I turned the audio to true (https://jsfiddle.net/3k89sy27/2/), I got the same error as above.
This example/demo page on getusermedia also garnered the same error: https://webrtc.github.io/samples/src/content/getusermedia/record/
Update: I've simplified the failure code even more.
navigator.mediaDevices.getUserMedia({
audio: true
}).then(function (stream) {
console.log(stream)
}).catch(console.log)
Audio does not want to register.....
Even tried FF's own Test Pilot and that failed too https://testpilot.firefox.com/experiments/voice-fill/

Answer 1

as #mrchestnut suggested, I downloaded Firefox Quantum (which was released as of Nov. 14th 2017) and it worked!
Blog Post on Mozilla:
https://blog.mozilla.org/blog/2017/11/14/introducing-firefox-quantum/
Download Quantum:
https://www.mozilla.org/en-US/firefox/new/?scene=2
Although this doesn't explain why it didn't work, it sure has sugar solved my problem.