GSC3510 rstp streaming


Hi, Im trying to stream a music file in GSC3510 so far I tried FFMPEG and it worked but only in multicast listening. this is the code:
ffmpeg -stream_loop -1 -re -i C:\relax.mp3 -vol 30 -filter_complex aresample=16000,aset samples=n=160 -acodec g722 -ac 1 -vn -f rtp udp://

If I use this code the music wont be interupted when a call is coming in because it understand that the call is already in place with the IP I used in the code.
what I want to do is stream music over application/music RTSP protocol, so that I can play music while some one tries to call and then music contiue on. I tried FFMPEG, Media555 (no luck at all) and gstreamer here I maniged to get the same resault as in FFMPEG. can someone please share some code and steps that I can finally use gsc3510 for rtsp streaming?