Video off should stop video rather than just mute it about jitsi-meet

[fippo]

writing up the plan for it...

1. get the peerconnections .localDescription.sdp
2. note the audio/video ssrcs
3. replace sendrecv with recvonly
4. setlocaldescription
5. update our presence in sld.jingle
6. take .remoteDescription.sdp
7. setremotedescription (oh, with a=sendrecv is is interesting... probably replace sendrecv with a=sendonly there)

[fippo]

ok, doing it as setLocalDescription-setRemoteDescription caused a role change. This apparently triggered a bug so now I'm always doing it the other way round, i.e. setRemoteDescription-createAnswer-mangledirection-setLocalDescription...

[emcho]

Just chatted with @fippo . This is essentially done except for two different cases:

1. calling it before we enter a session (in which case we simply need to remember a state and apply it later)
2. Act properly if this happens during ice negotiation. This would be trickier.

[fippo]

I think we would solve (1) differently, because applying it to the intial offer is easier than modifying the session mid-call
For (2) it seems this should actually be integrated into "modifySources" long-term which deals with the API brokenness... err... joy already. For now, we might just copy the strategy from there though.

What is missing is signalling. It seems SSRCs are retained, so we probably just need to add a mute-flag in the element.

[fippo]

reoping, not quite done.

1. signalling
2. hooking it up with the mute button

[emcho]

Good job @fippo !