Hello Juha,
The relay candidate is added only for RTP stream, but not for RTCP stream. Example: received SDP: v=0. o=- 3569961501 3569961501 IN IP4 192.168.2.104. s=cpc_med. c=IN IP4 192.168.2.104. t=0 0. m=audio 53528 RTP/AVP 0 101. a=sendrecv. a=rtpmap:0 PCMU/8000. a=rtpmap:101 telephone-event/8000. a=fmtp:101 0-15. a=ice-ufrag:3d6687c0. a=ice-pwd:165a6dbe. a=candidate:Hc0a80268 1 UDP 2130706431 192.168.2.104 53528 typ host. a=candidate:Hc0a80268 2 UDP 2130706430 192.168.2.104 49908 typ host.
sent SDP: v=0. o=- 3569961501 3569961501 IN IP4 192.168.2.2. s=cpc_med. c=IN IP4 192.168.2.2. t=0 0. m=audio 11070 RTP/AVP 0 101. a=sendrecv. a=rtpmap:0 PCMU/8000. a=rtpmap:101 telephone-event/8000. a=fmtp:101 0-15. a=ice-ufrag:3d6687c0. a=ice-pwd:165a6dbe. a=candidate:Hc0a80268 1 UDP 2130706431 192.168.2.104 53528 typ host. a=candidate:19216822 1 UDP 16777215 192.168.2.2 11070 typ relay. a=candidate:Hc0a80268 2 UDP 2130706430 192.168.2.104 49908 typ host.
We should have an extra candidate: a=candidate:19216822 1 UDP 16777215 192.168.2.2 11071 typ relay.
rtpproxy will allocate an extra port for RTCP traffic (RTP port + 1).
Regards, Ovidiu Sas