Below are some SDP examples you can use when working with RTP components.
First sample is a simple uLaw 8000/mono stream:
v=0 m=audio 5004 RTP/AVP 0 a=rtpmap:0 PCMU/8000/1
Since this is not a dynamic payload, receiver will not need additional SDP configuration.
ALaw 8000/mono stream:
v=0 m=audio 5004 RTP/AVP 8 a=rtpmap:8 PCMA/8000/1
Another non-dynamic payload, a MP3 streaming at 44100/stereo:
v=0 m=audio 0 RTP/AVP 14 a=rtpmap:14 mpa/44100/2
First dynamic payload sample is a simple PCM (uncompressed) 8000/16bits mono stream:
v=0 m=audio 0 RTP/AVP 98 a=rtpmap:98 L16/8000/1
Note, that this SDP setup must be applied on both transmitter and receiver, since dynamic payloads are not pre-defined in RFC.
Now we specify a Speex streaming at 16000 Hz:
v=0 m=audio 0 RTP/AVP 97 a=rtpmap:97 speex/16000 a=fmtp:97 mode="10,any"