Steps to reproduce: 1. Install QubesOS 2. Run firefox inside one of the Qubes VM. 3. Go to https://jsfiddle.net/W569n/3/ 4. Press "click here to start stream" Actual results: An error comes up : NotFoundError: The object can not be found here Expected results: Firefox should be able to find the audio input streams properly and ask the user which one to share with the page.
Thanks to some help on IRC, I've been able to pinpoint the problem to an interaction between ALSA and the media.navigator.audio.full_duplex option. If I disable this option, firefox starts acting as expected. I have a patch written that deactivate full_duplex when FF is compiled with USE_ALSA.
Not sure who was involved in the IRC conversation mentioned in comment 1.
That was me, in #firefox