The only reason (original) Skype existed was because there were, even at that time, not enough IPv4 addresses, so users who had public IPv4 address were tunneling data for users behind NAT. Small guy has no chance to create any kind of p2p communication app because he had no infrastructure like Skype. If everybody had public IPv4 address it would be trivial and also fast because of the direct connection. Video calls are hard but codec had nothing to do with it.