Hello, i have read your project requirement.
i can giver you perfect result as you want.
i have full experience on mobile app development and have done many video chatting and conference base base on webrtc.
if you want your own video conference server, i prefer you webrtc, kurento, jitsi.
this is open source video chatting service, so i can install this on your server and develop apps base on this.
or we can use twillio and quickblox, also.
thanks for you checking.
Best regards.