Video conferencing with high quality audio

Hello,

I'm looking for a video conferencing solution which offers high audio quality.

I have the following minimum requirements:

- high quality stereo audio for screen sharing (e.g. when presenting music/sound to your audience)
- A/V sync for screen sharing, not just for playing videos but for live demos with PD, Supercollider etc.
- preferably open source
- preferably self hostable
- multi platform or browser based
- easy to use for end users
- scalable up to 100 users (for presentations, lectures etc.)

Do you have any ideas?

Best,
Marc