Application-Defined RTCP Packets (APP)

The APP packet is intended for experimental use at developing new applications and features. Once a new APP RTCP packet type is test and found useful, it should be registered with the Internet Assigned Numbers Authority (IANA) as an original packet type.

 0               1               2               3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|V=2|P|   ST    |   PT=APP=204  |            length L           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                              SSRC                             |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                         name (ASCII) N                        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                  application-dependent data A                ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

V, P, PT, L:

As described for SR packets, with the packet type code set to 204 for verb|APP| packets.

ST:

5 bits
The subtype field allows a set of APP packets to be defined under one unique name, or provides any application-dependent data.

N:

4 octets
A name chosen by the person defining the set of APP packets to be unique with respect to other APP packets this application might receive.

A:

variable length
Application-dependent data may or may not appear in an APP packet.