Block diagram
RTCP is the Real-Time Control Protocol
This page hosts a formal specification of rtcp network payload (single udp packet) using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.
meta:
id: rtcp_payload
title: rtcp network payload (single udp packet)
xref:
justsolve: RTP
wikidata: Q749940
license: CC0-1.0
ks-version: 0.7
endian: be
doc: RTCP is the Real-Time Control Protocol
doc-ref: https://www.rfc-editor.org/rfc/rfc3550
seq:
- id: rtcp_packets
type: rtcp_packet
repeat: eos
types:
rtcp_packet:
seq:
- id: version
type: b2
- id: padding
type: b1
- id: subtype
type: b5
- id: payload_type
type: u1
enum: payload_type
- id: length
type: u2
- id: body
size: 4 * length
type:
switch-on: payload_type
cases:
'payload_type::sr': sr_packet
'payload_type::rr': rr_packet
'payload_type::sdes': sdes_packet
'payload_type::psfb': psfb_packet
'payload_type::rtpfb': rtpfb_packet
sr_packet:
seq:
- id: ssrc
type: u4
- id: ntp_msw
type: u4
- id: ntp_lsw
type: u4
- id: rtp_timestamp
type: u4
- id: sender_packet_count
type: u4
- id: sender_octet_count
type: u4
- id: report_block
type: report_block
repeat: expr
repeat-expr: _parent.subtype
instances:
ntp:
value: (ntp_msw << 32) & ntp_lsw
rr_packet:
seq:
- id: ssrc
type: u4
- id: report_block
type: report_block
repeat: expr
repeat-expr: _parent.subtype
report_block:
seq:
- id: ssrc_source
type: u4
- id: lost_val
type: u1
- id: highest_seq_num_received
type: u4
- id: interarrival_jitter
type: u4
- id: lsr
type: u4
- id: dlsr
type: u4
instances:
fraction_lost:
value: lost_val >> 24
cumulative_packets_lost:
value: lost_val & 0x00ffffff
sdes_packet:
seq:
- id: source_chunk
type: source_chunk
repeat: expr
repeat-expr: source_count
instances:
source_count:
value: _parent.subtype
source_chunk:
seq:
- id: ssrc
type: u4
- id: sdes_tlv
type: sdes_tlv
repeat: eos
sdes_tlv:
seq:
- id: type
type: u1
enum: sdes_subtype
- id: length
type: u1
if: type != sdes_subtype::pad
- id: value
size: length
if: type != sdes_subtype::pad
rtpfb_packet:
seq:
- id: ssrc
type: u4
- id: ssrc_media_source
type: u4
- id: fci_block
type:
switch-on: fmt
cases:
'rtpfb_subtype::transport_feedback': rtpfb_transport_feedback_packet
size-eos: true
instances:
fmt:
value: _parent.subtype
enum: rtpfb_subtype
rtpfb_transport_feedback_packet:
seq:
- id: base_sequence_number
type: u2
- id: packet_status_count
type: u2
- id: b4
type: u4
- id: remaining
size-eos: true
instances:
reference_time:
value: b4 >> 8
fb_pkt_count:
value: b4 & 0xff
packet_status:
size: 0
recv_delta:
size: 0
packet_status_chunk:
seq:
- id: t
type: b1
- id: s2
type: b2
if: t.to_i == 0
- id: s1
type: b1
if: t.to_i == 1
- id: rle
type: b13
if: t.to_i == 0
- id: symbol_list
type: b14
if: t.to_i == 1
instances:
s:
value: '(t.to_i == 0) ? s2 : (s1.to_i == 0 ? 1 : 0)'
psfb_packet:
seq:
- id: ssrc
type: u4
- id: ssrc_media_source
type: u4
- id: fci_block
type:
switch-on: fmt
cases:
'psfb_subtype::afb': psfb_afb_packet
size-eos: true
instances:
fmt:
value: _parent.subtype
enum: psfb_subtype
psfb_afb_packet:
seq:
- id: uid
type: u4
- id: contents
type:
switch-on: uid
cases:
0x52454d42: psfb_afb_remb_packet
size-eos: true
psfb_afb_remb_packet:
seq:
- id: num_ssrc
type: u1
- id: br_exp
type: b6
- id: br_mantissa
type: b18
- id: ssrc_list
type: u4
repeat: expr
repeat-expr: num_ssrc
instances:
max_total_bitrate:
value: br_mantissa * (1<<br_exp)
enums:
payload_type:
192: fir
193: nack
195: ij
200: sr
201: rr
202: sdes
203: bye
204: app
205: rtpfb
206: psfb
207: xr
208: avb
209: rsi
sdes_subtype:
0: pad
1: cname
2: name
3: email
4: phone
5: loc
6: tool
7: note
8: priv
psfb_subtype:
1: pli
2: sli
3: rpsi
4: fir
5: tstr
6: tstn
7: vbcm
15: afb
rtpfb_subtype:
1: nack
3: tmmbr
4: tmmbn
5: rrr
15: transport_feedback