Content for TS 26.522 Word version: 18.1.0
B Examples of SDP offers and answers
B.1 SDP example for RTP header extension for XR pose
C RTP Header Extension for Absolute Sender Time
D IANA registration information for RTP Header Extensions
D.1 Introduction
D.2 urn:3gpp:pdu-set-marking:rel-18
D.3 urn:3gpp:xr-pose
D.4 urn:3gpp:delay-measurement-response:rel-18
E IANA registration information for RTCP XR block types
E.1 Introduction
E.2 Timing Information for QoE Metrics Calculation
$ Change history
B Examples of SDP offers and answers p. 31
B.1 SDP example for RTP header extension for XR pose p. 31
An example SDP description using the RTP HE for XR pose (defined in clause 4.3) is presented below. Using the extension attribute media, the RTP HE for XR pose with URI urn:3gpp:xr-pose provided in the video stream with MID m1 is also applicable to another video stream with MID m2.
C RTP Header Extension for Absolute Sender Time p. 31
The information below is about the "RTP Header Extension for Absolute Sender Time" and it was retrieved from https://webrtc.googlesource.com/src/ +/refs/heads/main/docs/native-code/rtp-hdrext/abs-send-time on January 31, 2024.
Absolute Send Time
The Absolute Send Time extension is used to stamp RTP packets with a timestamp showing the departure time from the system that put this packet on the wire (or as close to this as we can manage). Contact solenberg@google.com for more info.
Name:
"Absolute Sender Time" ; "RTP Header Extension for Absolute Sender Time"
Formal name:
SDP "a=name":
"abs-send-time" ; this is also used in client/cloud signaling.
Not unlike RTP with TFRC
Wire format:
1-byte extension, 3 bytes of data. total 4 bytes extra per packet (plus shared 4 bytes for all extensions present: 2 byte magic word 0xBEDE, 2 byte # of extensions). Will in practice replace the "toffset" extension so we should see no long term increase in traffic as a result.
Encoding:
Timestamp is in seconds, 24 bit 6.18 fixed point, yielding 64s wraparound and 3.8us resolution (one increment for each 477 bytes going out on a 1Gbps interface).
Relation to NTP timestamps:
abs_send_time_24 = (ntp_timestamp_64 >> 14) & 0x00ffffff ; NTP timestamp is 32 bits for whole seconds, 32 bits fraction of second.
Notes:
Packets are time stamped when going out, preferably close to metal. Intermediate RTP relays (entities possibly altering the stream) should remove the extension or set its own timestamp.
D IANA registration information for RTP Header Extensions p. 32
D.1 Introduction p. 32
This Annex provides the RTP HE registration information that is referenced from the IANA registry at http://www.iana.org/ .
D.2 urn:3gpp:pdu-set-marking:rel-18 p. 32
The desired extension naming URI:
urn:3gpp:pdu-set-marking:rel-18
A formal reference to the publicly available specification:
TS 26.522
A short phrase describing the function of the extension:
PDU Set marking and signalling of end of data burst, see clause 4.2
Contact information for the organization or person making the registration:
3GPP Specifications Manager
3gppContact@etsi.org
+33 (0)492944200
D.3 urn:3gpp:xr-pose p. 32
The desired extension naming URI:
urn:3gpp:xr-pose
A formal reference to the publicly available specification:
TS 26.522
A short phrase describing the function of the extension:
Signalling of a 6DoF or 3DoF XR pose, see clause 4.3
Contact information for the organization or person making the registration:
3GPP Specifications Manager
3gppContact@etsi.org
+33 (0)492944200
D.4 urn:3gpp:delay-measurement-response:rel-18 p. 33
The desired extension naming URI:
urn:3gpp:delay-measurement-response:rel-18
A formal reference to the publicly available specification:
TS 26.522
A short phrase describing the function of the extension:
In-band end-to-end delay measurement, see clause 4.4
Contact information for the organization or person making the registration:
3GPP Specifications Manager
3gppContact@etsi.org
+33 (0)492944200
E IANA registration information for RTCP XR block types p. 33
E.1 Introduction p. 33
This Annex provides the RTCP XR block type and SDP parameter registration information that is referenced from the IANA registry at http://www.iana.org/ .
E.2 Timing Information for QoE Metrics Calculation p. 33
This document assigns the block type value TBD in the IANA "RTP Control Protocol Extended Reports (RTCP XR) Block Type Registry" to the "Timing Information for QoE Metrics Calculation Block".
The desired, corresponding SDP parameter name in the "RTP Control Protocol Extended Reports (RTCP XR) Session Description Protocol (SDP) Parameters Registry":
qoe-timing-info
A formal reference to the publicly available specification:
TS 26.522
Contact information for the organization or person making the registration:
3GPP Specifications Manager
3gppContact@etsi.org
+33 (0)492944200
$ Change history p. 34
