Open source video conference cross platform native clients

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video

WebRTC

For weeks I have been researching to find an open source video conferencing platform that allows integration from native clients. I am developing a solution that would need to communicate from a native app via a windows dll (at least initially). Ultimately, I want develop my application for any OS to talk to it natively. A lot of platforms provide the JavaScript interface (like Jitsi) but wrapping this in a windows dll is both complicated and has a huge footprint. What open source video conference servers are available that have native windows clients that can be packaged in a DLL?

What I have tried:

I have looked at Jitsi, Janus, AntMedia, Kurento and some others but everything goes back to browser technology.