We’ve developed such an environment based on Jitsi for webinars of Barcelona City Council.
So far we’had up to 9 hosts and 152 viewers, but the same architecture could handle at least 500 concurrent users with microphone and cameras closed. Besides, we’re handling public meetings of up to 200 local government agencies and municipalities and several other private companies.
In order to ensure 1000+ viewers on the same Jitsi room, some testing might be done, and it’s not 100% clear that jitsi could even support it. For our experience, at least 500 would be possible with a cluster of several videobridge servers.
We’ve also used a private streaming service for viewers, so we can host > 1.000 viewers without issues, but then moving them into host will be more complicated if you don’t have an easy way of chatting with them. Maybe a private XMPP chat embedded on the same page as the video player would do it, so you can send someone a link to join as another host, but then, kicking him forever will be quite complicated in Jitsi.
Right now we’re testing a feature to open/close microphones and cameras remotely, so you could bring them to de-facto “host mode”, thus giving them floor to participate and then closing their mic&cam afterwards.
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