This ought to be in the wiki
The command line is :
gst-launch-1.0 udpsrc address=224.0.0.56 port=46194 caps="application/x-rtp, media=audio, payload=10, clock-rate=44100" ! .recv_rtp_sink_0 rtpbin ! rtpL16depay ! audioconvert ! audioresample ! alsasink device=hw:0,0
gst-launch-1.0 udpsrc address=224.0.0.56 port=45678 caps="application/x-rtp, media=audio, payload=10, clock-rate=44100" ! .recv_rtp_sink_0 rtpbin ! rtpL16depay ! audioconvert ! audioresample ! alsasink device=hw:1,0
Of course, you adjust the sink how you want and update the port number according to the method given on the above page of the wiki (tcpdump -n net 224.0.0.0/8 -c 10
).