I have a Panasonic PV DV-953 camcorder connected via Firewire to a Mac Mini running OS X 10.10.2. It works in Facetime, etc, but Firefox doesn't see it. In #media, it's theorized that it's related to the video format used by the DV camcorder not being one we support. Could be that it doesn't support YUV, or that the compression is not one we support decompressing. This needs investigation but is not a common use case, so not a priority.
Here's the MDN sample I was using to try to figure this out: http://mdn-samples.mozilla.org/s/webrtc-capturestill/
Mass change P4->P5 to align with new Mozilla triage process.