RTP Control Protocol: Difference between revisions

Revision as of 02:14, 8 August 2024

Revision as of 08:31, 5 March 2025

Line 42:

==Packet header==

{{APHD|start|title=RTCP packet header{{Ref RFC|3550}}}}

{| class="wikitable" style="text-align:center"

{{APHD|0|bits1=2|field1=Version|field2=P|bits3=5|field3=RC|bits4=8|field4=PT|bits5=16|field5=Length}}

|+RTCP packet header

{{APHD|4|bits1=32|field1=SSRC Identifier}}

!''Offsets''

{{APHD|end}}

!Octet

* ''';{{APHD|def|name=Version''': (|length=2 bits) |text=Identifies the version of RTP, which is the same in RTCP packets as in RTP data packets. The version defined by this specification is two (2).<ref name=RFC3550/>}}

! colspan="8" |0

* ''';{{APHD|def|name=Padding|short=P (Padding)''': (|length=1 bits) bit|text=Indicates if there are extra padding bytes at the end of the RTP packet. Padding may be used to fill up a block of certain size, for example as required by an encryption algorithm. The last byte of the padding contains the number of padding bytes that were added (including itself).<ref name=RFC3550/>}}

! colspan="8" |1

* '''RC (;{{APHD|def|name=Reception reportReport count)''': (Count|short=RC|length=5 bits) |text=The number of reception report blocks contained in this packet. A value of zero is valid.<ref name=RFC3550/>}}

! colspan="8" |2

*;{{APHD|def|name=Packet '''Type|short=PT (Packet type)''': (|length=8 bits) |text=Contains a constant to identify RTCP packet type.<ref name=RFC3550/>}}

! colspan="8" |3

* ''';{{APHD|def|name=Length''': (|length=16 bits) |text=Indicates the length of this RTCP packet (including the header itself) in 32-bit units minus one.<ref name=RFC3550/>}}

|-

* ''';{{APHD|def|name=SSRC''': (Identifier|length=32 bits) |text=''Synchronization sourceSource identifierIdentifier'' uniquely identifies the source of a stream.<ref name=RFC3550/>}}

!Octet

! Bit {{efn|Bits are ordered most significant to least significant; bit offset 0 is the most significant bit of the first octet. Octets are transmitted in [[network order]]. Bit transmission order is medium dependent.}}

! 0

!1

! colspan="1" | 2

! colspan="1" | 3

!4

!5

!6

!7

! colspan="1" | 8

!9

!10

!11

!12

!13

!14

!15

!16

!17

!18

!19

!20

!21

!22

!23

!24

!25

!26

!27

!28

!29

!30

!31

|- align="center"

!

! 0

| colspan="2" |Version

| colspan="1" |P

| colspan="5" |RC

| colspan="8" |PT

| colspan="16" |length

|- align="center"

!

! colspan="1" |32

| colspan="32" |SSRC identifier

|- align="center"

|}

* '''Version''': (2 bits) Identifies the version of RTP, which is the same in RTCP packets as in RTP data packets. The version defined by this specification is two (2).<ref name=RFC3550/>

* '''P (Padding)''': (1 bits) Indicates if there are extra padding bytes at the end of the RTP packet. Padding may be used to fill up a block of certain size, for example as required by an encryption algorithm. The last byte of the padding contains the number of padding bytes that were added (including itself).<ref name=RFC3550/>

* '''RC (Reception report count)''': (5 bits) The number of reception report blocks contained in this packet. A value of zero is valid.<ref name=RFC3550/>

* '''PT (Packet type)''': (8 bits) Contains a constant to identify RTCP packet type.<ref name=RFC3550/>

* '''Length''': (16 bits) Indicates the length of this RTCP packet (including the header itself) in 32-bit units minus one.<ref name=RFC3550/>

* '''SSRC''': (32 bits) ''Synchronization source identifier'' uniquely identifies the source of a stream.<ref name=RFC3550/>

Note that multiple reports can be concatenated into a single compound RTCP packet, each with its own packet header.