The talk is about video conferencing with the Linphone open source VoIP client that implements the SIP protocol. It delves into the selective forwarding unit architecture for modern video conferencing systems that has advantages over media mixer architecture. The talk focuses on what is required on the SIP client part to be able to interact with this kind of video conferencing system. The speaker also mentions possible evolutions such as implementing the Xcon conferencing server and adding end-to-end encryption to this video conferencing server.