30 participants experience

Hi,
I have setup now a few jitsi systems, the goal is for sessions with about 30 people, and maybe a few of them at a time.

We did now a larger test with 25 participants and I want to share some experience, and issues, and questions.

Setup
System: Ubuntu 18.04LTS
Server: AWS m5n.2x large 8 vCPU, 32 GB RAM, up to 25 GB network
Jitsi install, following


and

Jitsi Meet Versions: 1.0.4101-1 500

Extra Configs of jitsi meet:
startAudioMuted: 5,
resolution: 480, (I dont think this does anything actually)
gatherStats: false,

Test

  • about 25 people
  • various browsers as well as mobile devices
  • tested with video on and off

Results

  • Running the test with 25 people gave the following rough stats:
    CPU: about 35%, Mem: 7 %, network: about 150 Mbit
  • mobile phones seemed more stable than browser
  • laptops got really hot
  • most folks likely used grid view, because it is impressive

Problems

  • even with a smaller number of participants with get massive lipsync (video/audio delays)
  • with this big machine, I think up to 15 people it seemed to work ok, very nice in grid view actually
  • but then we got almost randomly people drop out or get marked as inaktiv and then avail again, or video disappeared and came back, we never saw more than 15 or so with video on
  • the little connectivity indicator for users in the browser seems really really random, user A sees user C as bad connection, user B sees user C as very good condition, and things go on and off all the time

Errors
140 MB jvb logs in 1 hour

  • I see a lot of them:
    org.jitsi.videobridge.EndpointMessageTransport.log() Failed to send a message over a WebRTC data channel (endpoint=6473fdc7):
  • I see this in jicofo
    org.jitsi.jicofo.LipSyncHack.log() No corresponding audio found for: XXXX.de/80770de8 ‘source-add’ to: XXXXX.de/78b4634b

Questions

  • how the hell are you doing reliable sessions with 30 people ? :wink:
  • does the machine size sound reasonable?
  • what error logs would be good to look for?
  • would set constraints of video resolution max size to 240 sound like a good idea?
  • what other option could provide more stability?
  • how do I configure the undocumented settings about lipsync, or what can be done about that?
  • what can be done to reduce the load on the client?
    — is there an option to allow max 5 people wit video at a time?
    — is there an option to prevent guests to use grid view, and have always the moderator visible?
  • is there an option to prevent grid view all together?
  • how can I disable: “LipSyncHack” I thought it is disabled by default

What else would you recommend?

Our use case is basically for schools, having a teacher and all 30 students in a Jitsi Room.

One more thing, I noticed, limiting video resolution works for browser (obviously, because it is meet), but mobile phones are still sending high res video. Is there a way to prevent this?

We are using two measures to limit the amount of video being transmitted (and have had good success with conferences of about 20 people):

  • in jitsi-config.js set the channelLastN parameter to 3 (only the last three speakers video streams will be trasmitted)
  • in the same file, set startVideoMuted: 3,. All participants after the third will start with video muted
  • same for startAudioMuted

cheers
jc

1 Like

Hi jc
I think this config channelLastN helped a lot. With the docu about this config I would have never guessed what this does :wink:
We had a pretty good chat with 15 people.
I also found the config to disable the lipsync thing, if that did anything, I think it got a bit better.

Btw, we also had a test call on meet.jit.si, tonight and in 10 minutes we had 3 cases where everyone was completely frozen for 15 seconds.

Thanks again,
PD

Can you please specific location/path for the file jitsi-config.js

Found the location /etc/jitsi/meet/ionameet.tk-config.js
where ionameet.tk is the name of the domain where Jitsi is hosted

Hi PD123,
thanks for sharing your experience.
Did you have further improvements on your setup?
I’m working on a similar project, I just finished to install my Jitsti Meet server and your know-how could be very useful in this phase.

Thank you

Hi
no further improvements on the setup.
It is still kinda difficult for some users to get a stable connection, and some users devices have issues.

Peter