There is no limitation except driven by architecture. Usually there is a limit on how many you can do without putting a conference server, 5 is quite okay for

There is no limitation except driven by architecture. Usually there is a limit on how many you can do without putting a conference server, 5 is quite okay for HD video on a laptop. Typically in these cases (mesh scenarios) the CPU/memory is a limitation than capacity. Upto 10, if everyone is doing SD video. So services pick a number 7 or 8 to limit the participants in a video some doing HD, some doing SD. This number is smaller if you pick iPad/tablets and higher if you are on a MacPro or something with multiple GPUs (possibly in these cases limited by capacity). If the service builds a MCU (or conference bridge) those typically do not have such limitations, it then depends on how you multiplex the streams, mix them or selectively forward them, if the server is just forwarding packets, or decrypting them and re-encrypting them because it is transcoding or re-writing RTP headers, etc.