Audio quality poor


I (in the US) was videoconferencing with someone in Europe using my new server’s new jitsi setup.
All of the logins worked fine, but the audio and video quality were both poor. I lowered the video quality down to poorest, and then the video lost its stutter, but the European side reported low audio quality. We shutoff video and there was no change. Both sides had very good connections. Independent measurements of bandwidth were about 8mbps up and down in Europe, and even better in the states. The bandwidth reported by jitsi was about 2.5mbps up and down.

Does anyone know how to improve things? It is unusable as is.
My end and the server are both running Ubuntu. The participant in Europe was using an iPad with the app installed.

Addendum: Actually, we also tried and had the same issues.