Pass unparsed user session description to soa session object.
User SDP is used as basis for SDP Offer/Answer negotiation. It can be very minimal, listing just m= lines with the port numbers and RTP payload numbers of supported codecs, like
SOATAG_USER_SDP_STR("m=audio 5004 RTP/AVP 0 8")
When generating the offer or answer the user SDP is augmented with the required SDP lines (v=, o=, t=, c=, a=rtpmap, etc.) as required. The complete offer or answer generated by is passed in SOATAG_LOCAL_SDP_STR() (SOATAG_LOCAL_SDP() contains session in parsed format).
Corresponding tag taking reference parameter is SOATAG_USER_SDP_STR_REF()