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"

SDP – RFC 4566
RTP profile – RFC 3551