rtpmap Attribute

The rtpmap attribute takes the form:

a=rtpmap:<payloadType> <encodingName>/<clockRate>[/audioChannels]

payloadType: contains a dynamically-assigned RTP payload type as specified in RFC 3551, RTP Profile for Audio and Video Conferences with Minimal Control. The Internet Assigned Numbers Authority (IANA) has designated RTP payload types 96 through 127 as available for dynamic assignment.

encodingName: contains the codec identifier (AMR or AMR-WB in the following tables).

clockRate: contains the sampling rate.

audioChannels: (used only for audio streams, and optional) contains the number of audio channels — not used in transcoding decisions.