Experiences with conferences and online school (max 15 ppl)

While I don’t think this is all unknown or new, let me share our tests with Jitsi(Meet). We have been looking for audio/video chat tools for both schools and business due to current Doomsday scenarios.

This was on jvb1 and some 6-7 years old java since it was the state-of-the-art until very recently.

The fist obvious program to test was Jitsi. I have installed a plain unhacked server on a container (yes, really, and works pretty well), set up monitoring (it was working only with java8), and let it go. Without much bullshitting:

  • with about 10 participants
  • the server load was almost negligible
  • the bandwidth was about 1 Mbps per participant on the server (which wasn’t important since the server sits on some multi-gigs link)
  • the clients ran more-or-less without problems.

(Some stats give really weird numbers, for the record. If anyone interested in the Netdata chart plugin, just ping me on matrix as @grin:grin.hu or on #jitsimeet:matrix.org.)

However. After raising participants above the magical 15, the server was still very happy, the bandwith was okay, but the clients started dying. Even with one videostream and 15 non-video partially muted participants they repeatedly lose connection, reconnect, an often the video (the one and only) get grayed out and stays there while the voice goes on (only fo some), and only client reload fixes it. The mobile client sometimes lose video “permanently” since it’s not that easy to restart it as the desktop version. It seems that slow participants make the fast ones disconnect, too.

A fellow looked at the desktop webpage code and mentioned several ugly problems, like buffering pouring insane amounts of data on the other participants after reconnecting and similar issues, but they seem to be hard to fix, though not impossible - but I’m just the messenger here.

So, anyway, it didn’t work well above 15 people, also had various problems on various browsers (like not seeing cam/mic on Safari/Mac, sometimes not seeing cam on Firefoxen).
It seems that the biggest obstacle is the client here - html5 and lots and lots of javascript I presume.

[As for contrast BigBlueButton works pretty well and stable (still I want to make a test with more than a dozen participants, my install is way too fresh), but it’s very different as far as I see. For larger conferences we probably have to use BBB, unless there are mobile clients which are clunky there.]

You should not use Firefox in your tests, currently Firefox has no simulcast so it brings extra 5Mb/s per client from every Firefox that joins … we are aware of that problem, if you open meet.jit.si with Firefox you will see a warning for using that browser. We are working on changing that, but for the time being Chrome is your best shot.
It is possible that adding one or two Firefox users to 15 participants can make the experience bad for the rest, especially the mobile users.

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Interesting. I don’t remember reading this in the docs, which of course doesn’t mean it isn’t there. :slight_smile:

Where’s that 5Mbps? Server up/down or client up/down? (The server doesn’t quite care but the clients seemed to be pretty busy.)

The browsers were the choice of the participants and I wasn’t aware of the need to suggest otherwise. I’ll ask them to repeat it with Chromium.

So Chrome sends simulcast, this is up to 3 layers of video 180p, 360p and 720p. And the bridge is sending to clients the max one if the participant is on stage or 180p if shown in a thumbnail (depends what is the client watching).
Firefox in our code does not support simulcast, so it sends 720p which is 5Mb/s let’s say. There is nothing to be dropped like layers from the bridge, so that feed is just forwarded to clients. So if you have 3 Firefox users in 720p in thumbnails and one Chrome on large screen you will be getting an extra 15Mb/s data just because of those FF. So 20Mb/s of 720p data and few Mb/s more for the rest of the thumbs and audio.
We expect to land FF simulcast in few weeks on meet.jit.si (it may happen it is next week), so stay tuned for news. You can monitor this issue for updates: https://github.com/jitsi/jitsi-meet/issues/4758

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