Hi Sebastian, I'll try this approach this evening. The signalling protocol I'm developing is the SIP protocol. Sip is the standard for voip application like linphone. They use a symmetric rtp to solve issues with nat and firewall. <div class="gmail_quote">Il 04/nov/2013 10:01 "Sebastian Dröge" <<a href="mailto:sebastian@centricular.com">sebastian@centricular.com</a>> ha scritto: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> On So, 2013-11-03 at 16:19 +0100, Elio Francesconi wrote: > Hi Sebastian, > I’ve found the issue, it is due to VoIP protocol, how it opens the rtp streams are opened by the endpoint. > > My soft phone (linphone again) want a symmetric RTP and changes the destination port in case “udpsink” and “udpsrc” differs. > This is the scenario: > > PIPELINE#1 > audiotestsrc ! audioconvert ! alawenc ! rtppcmapay ! udpsink host=192.168.1.6 port=7078 > > PIPELINE#2 > rtpbin udpsrc caps=application/x-rtp,media=(string)audio,clock-rate=(int)8000,encoding-name=(string)PCMA port=5008 ! rtppcmadepay ! alawdec ! audioconvert ! audioresample ! osxaudiosink > > > GSTREAMER ————————————————> LINPHONE > ipadders: 192.168.1.3 ipaddress: 192.168.1.6 > port(random): 57401 PORT: 7078 > > GSTREAMER <--------------------------------------------------- LINPHONE > ipadders: 192.168.1.3 ipaddress: 192.168.1.6 > port(random): 5008 PORT: 7078 > > I was expecting this behaviour, but linphone sends the rtp packets to 57401 instead of 5008 (symmetric RTP) > > > So I was wondering if it is possible solving the issue creating the pipeline#1 using source port defined by the user, in my case: 5008 You can use the bind-port property on udpsink/multiudpsink for this probably. How exactly does the linphone protocol work though? How does it know where to send what kind of data? Is there another protocol on top of RTP that negotiates all this? -- Sebastian Dröge <<a href="mailto:sebastian@centricular.com">sebastian@centricular.com</a>> Centricular Ltd - <a href="http://www.centricular.com" target="_blank">http://www.centricular.com</a> Expertise, Straight from the Source _______________________________________________ gstreamer-devel mailing list <a href="mailto:gstreamer-devel@lists.freedesktop.org">gstreamer-devel@lists.freedesktop.org</a> <a href="http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel" target="_blank">http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel</a> </blockquote></div>