A.5 SDP offers for text

26.1143GPPIP Multimedia Subsystem (IMS)Media handling and interactionMultimedia telephonyRelease 18TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

A.5.1 T.140 with and without redundancy

An offer to use T.140 real-time text may be realized by using SDP according to the following example in session setup or for addition of real-time text during a session.

Table A.5.1: Example SDP offer for T.140 real-time text

SDP offer

m=text 53490 RTP/AVP 100 98

b=AS:2

b=RS:0

b=RR:500

a=rtpmap:100 red/1000/1

a=rtpmap:98 t140/1000/1

a=fmtp:100 98/98/98

The example in table A.5.1 shows that RTP payload type 98 is used for sending text without redundancy, whereas RTP payload type 100 is used for sending text with 200 % redundancy. IPv4 addressing is assumed in the computation of bandwidth values.