Improve amount of signaling messages when joining a call

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Steps to reproduce

Have an ongoing call with about 55 participants
Join the call

Expected behaviour

You receive a reasonable amount of signaling messages

Actual behaviour

In the first 26s you receive around 1070 signaling messages.

Details

Received signaling messages by type:

   1         type = answer;
  16         type = offer;
   1         type = answer;
 695         type = mute;
 351         type = nickChanged;
  16         type = offer;
  7          type = unmute;

https://github.com/nextcloud/spreed/pull/4181 implemented a mechanism to make sure that the initial status of all participants is actually received, which results in a high amount of signaling messages in the first 30s after joining a call. Additionally to those signaling message, some messages are also send/received via the webrtc data channel (nickChanged for example).

Some ideas

Check that the messages from https://github.com/nextcloud/spreed/pull/4181 are sent only to the newly joined participant
Only send speaking/speakingStopped messages through data channel, use signaling for everything else (only possible after all clients support all signaling message types)
Ignore data channel messages client side, when the type is supported as a signaling message
Introduce some kind of state message where nickChanged, mute (audio/video) and raisedHand are combined into one single message
According to https://github.com/nextcloud/spreed/pull/4181 it is not possible to detect when to send the initial state to a newly joined participant. We could think about letting the newly joined participant request the state, this way it would be 1 message to all (the new participant requesting the state) and 1 message from each participant to the new participant (the actual state), so 56 messages in total.

nextcloud / spreed