Answering a video call (from Android!) does not send an SDP answer when there is no camera

[reivilibre]

Steps to reproduce

1. Start a video call from Element Android to a user using Element Web
2. Answer the call on Element Web

Outcome

What did you expect?

• To see the caller's video feed
  • this is what happens when you initiate a call from Element Web(!)

What happened instead?

• The call remains forever in the 'Connecting' state until it eventually times out (the caller gets a message saying the callee didn't answer)
• Firefox's about:webrtc shows that no Local SDP Answer is being sent
• Firefox's console is showing lots of activity. It appears to the naïve eye that Element is stuck in a loop trying to request permission to use the camera, but it's automatically failing.

Operating system

Linux

Application version

Element version: 1.11.2 Olm version: 3.2.12

How did you install the app?

Ubuntu PPA

Homeserver

librepush.net & other internal use homeserver

Will you send logs?

Yes

N.B. The logs are from the desktop application reproducing the same effect, but my debugging (where I refer to Firefox) has been on a private internal homeserver

[dbkr]

From the logs, element-web has got very confused on whether it's supposed to be answering with video or not, and has ended up calling getUserMedia with neither audio nor video which is obviously quite broken.

[dbkr]

I can't reproduce this calling from Android though - perhaps the Android device in question is sending an offer with no audio or video?