The IMS: IP Multimedia Concepts And Services, Second Edition

15.4. RTP profile and payload format specification for audio and video (RTP/AVP)

As defined in Section 15.3, an application using RTP must specify a profile and the payload formats used for it. In this section the profile and payload formats for audio and video applications are identified (the full specifications are defined in a combined document in [RFC3551]). Table 15.1 contains a summary of the profile specified for audio and video application and Table 15.2 contains a sample of the payload formats specified for audio and video.

15.4.1. Static and dynamic payload types

A static payload type is defined with a fixed identification number, a clock rate and a number of channels, when applicable. A dynamic payload type is defined without a number, but a number is dynamically allocated. Dynamic payload types are assigned numbers between 96 and 127.

Table 15.1. RTP/AVP-specific profile.

Profile item	RTP/AVP-specific
RTP data header	Fixed RTP data header is used (1 marker bit)
Payload types	Defined below
RTP header additions	None
RTP header extensions	None
RTCP extension packet types	None
RTCP report interval	As recommended in [RFC3550]
SR/RR extensions	None
SDES use	As defined in [RFC3550]
Security	RTP default
String-to-key mapping	None
Congestion	[RFC1633] and [RFC2475] can be used, as can best effort services
Underlying protocol	UDP, TCP
Transport mapping	Standard mapping of RTP/RTCP to transport-level addresses
Encapsulation	Not specified

Table 15.2. Sample payload formats for audio and video.

PT	Encoding name ...