draft-ietf-avtcore-clksrc-06.txt   draft-ietf-avtcore-clksrc-07.txt 
Audio/Video Transport Core A. Williams Audio/Video Transport Core Maintenance A. Williams
Maintenance Audinate Internet-Draft Audinate
Internet-Draft K. Gross Intended status: Standards Track K. Gross
Intended status: Standards Track AVA Networks Expires: April 05, 2014 AVA Networks
Expires: March 14, 2014 R. van Brandenburg R. van Brandenburg
H. Stokking H. Stokking
TNO TNO
September 10, 2013 October 02, 2013
RTP Clock Source Signalling RTP Clock Source Signalling
draft-ietf-avtcore-clksrc-06 draft-ietf-avtcore-clksrc-07
Abstract Abstract
NTP format timestamps are used by several RTP protocols for NTP format timestamps are used by several RTP protocols for
synchronisation and statistical measurements. This memo specifies synchronisation and statistical measurements. This memo specifies
SDP signalling identifying timestamp reference clock sources and SDP SDP signalling identifying timestamp reference clock sources and SDP
signalling identifying the media clock sources in a multimedia signalling identifying the media clock sources in a multimedia
session. session.
Requirements Language Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
Status of this Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
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This Internet-Draft will expire on March 14, 2014. This Internet-Draft will expire on April 05, 2014.
Copyright Notice Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Applications . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Applications . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Timestamp Reference Clock Source Signalling . . . . . . . . . 6 4. Timestamp Reference Clock Source Signalling . . . . . . . . . 5
4.1. Clock synchronization . . . . . . . . . . . . . . . . . . 6 4.1. Clock synchronization . . . . . . . . . . . . . . . . . . 5
4.2. Identifying NTP Reference Clocks . . . . . . . . . . . . . 7 4.2. Identifying NTP Reference Clocks . . . . . . . . . . . . 6
4.3. Identifying PTP Reference Clocks . . . . . . . . . . . . . 7 4.3. Identifying PTP Reference Clocks . . . . . . . . . . . . 6
4.4. Identifying Global Reference Clocks . . . . . . . . . . . 9 4.4. Identifying Global Reference Clocks . . . . . . . . . . . 8
4.5. Private Reference Clocks . . . . . . . . . . . . . . . . . 9 4.5. Private Reference Clocks . . . . . . . . . . . . . . . . 8
4.6. Local Reference Clocks . . . . . . . . . . . . . . . . . . 9 4.6. Local Reference Clocks . . . . . . . . . . . . . . . . . 8
4.7. Traceable Reference Clocks . . . . . . . . . . . . . . . . 9 4.7. Traceable Reference Clocks . . . . . . . . . . . . . . . 8
4.8. SDP Signalling of Timestamp Reference Clock Source . . . . 9 4.8. SDP Signalling of Timestamp Reference Clock Source . . . 8
4.8.1. Examples . . . . . . . . . . . . . . . . . . . . . . . 11 4.8.1. Examples . . . . . . . . . . . . . . . . . . . . . . 10
5. Media Clock Source Signalling . . . . . . . . . . . . . . . . 13 5. Media Clock Source Signalling . . . . . . . . . . . . . . . . 12
5.1. Asynchronously Generated Media Clock . . . . . . . . . . . 13 5.1. Asynchronously Generated Media Clock . . . . . . . . . . 12
5.2. Direct-Referenced Media Clock . . . . . . . . . . . . . . 13 5.2. Direct-Referenced Media Clock . . . . . . . . . . . . . . 12
5.3. Stream-Referenced Media Clock . . . . . . . . . . . . . . 14 5.3. Stream-Referenced Media Clock . . . . . . . . . . . . . . 14
5.4. SDP Signalling of Media Clock Source . . . . . . . . . . . 16 5.4. SDP Signalling of Media Clock Source . . . . . . . . . . 15
5.5. Examples . . . . . . . . . . . . . . . . . . . . . . . . . 17 5.5. Examples . . . . . . . . . . . . . . . . . . . . . . . . 17
6. Signalling Considerations . . . . . . . . . . . . . . . . . . 19 6. Signalling Considerations . . . . . . . . . . . . . . . . . . 18
6.1. Usage in Offer/Answer . . . . . . . . . . . . . . . . . . 19 6.1. Usage in Offer/Answer . . . . . . . . . . . . . . . . . . 19
6.1.1. Indicating Support for Clock Source Signalling . . . . 20 6.1.1. Indicating Support for Clock Source Signalling . . . 19
6.1.2. Timestamp Reference Clock . . . . . . . . . . . . . . 20 6.1.2. Timestamp Reference Clock . . . . . . . . . . . . . . 19
6.1.3. Media Clock . . . . . . . . . . . . . . . . . . . . . 20 6.1.3. Media Clock . . . . . . . . . . . . . . . . . . . . . 19
6.2. Usage Outside of Offer/Answer . . . . . . . . . . . . . . 21 6.2. Usage Outside of Offer/Answer . . . . . . . . . . . . . . 20
7. Security Considerations . . . . . . . . . . . . . . . . . . . 21 7. Security Considerations . . . . . . . . . . . . . . . . . . . 20
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20
8.1. Reference Clock SDP Parameter . . . . . . . . . . . . . . 22 8.1. Reference Clock SDP Parameter . . . . . . . . . . . . . . 21
8.2. Media Clock SDP Parameter . . . . . . . . . . . . . . . . 22 8.2. Media Clock SDP Parameter . . . . . . . . . . . . . . . . 21
8.3. Timestamp Reference Clock Source Parameters Registry . . . 23 8.3. Timestamp Reference Clock Source Parameters Registry . . 22
8.4. Media Clock Source Parameters Registry . . . . . . . . . . 24 8.4. Media Clock Source Parameters Registry . . . . . . . . . 23
8.5. Source-level Attributes . . . . . . . . . . . . . . . . . 25 8.5. Source-level Attributes . . . . . . . . . . . . . . . . . 24
8.5.1. Source-level Timestamp Reference Clock Attribute . . . 25 8.5.1. Source-level Timestamp Reference Clock Attribute . . 24
8.5.2. Source-level Media Clock Attribute . . . . . . . . . . 25 8.5.2. Source-level Media Clock Attribute . . . . . . . . . 24
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 25 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 24
9.1. Normative References . . . . . . . . . . . . . . . . . . . 25 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 24
9.2. Informative References . . . . . . . . . . . . . . . . . . 26 10.1. Normative References . . . . . . . . . . . . . . . . . . 24
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 27 10.2. Informative References . . . . . . . . . . . . . . . . . 26
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27
1. Introduction 1. Introduction
RTP protocols use NTP format timestamps to facilitate multimedia RTP protocols use NTP format timestamps to facilitate multimedia
session synchronisation and for providing estimates of round trip session synchronisation and for providing estimates of round trip
time (RTT) and other statistical parameters. time (RTT) and other statistical parameters.
Information about media clock timing exchanged in NTP format Information about media clock timing exchanged in NTP format
timestamps may come from a clock which is synchronised to a global timestamps may come from a clock which is synchronised to a global
time reference, but this cannot be assumed nor is there a time reference, but this cannot be assumed nor is there a
skipping to change at page 5, line 20 skipping to change at page 4, line 23
video projectors, or television sets tiled together contiguously video projectors, or television sets tiled together contiguously
or overlapped in order to form one large screen. Each of the or overlapped in order to form one large screen. Each of the
screens reproduces a portion of the larger picture. In some screens reproduces a portion of the larger picture. In some
implementations, each screen or projector may be individually implementations, each screen or projector may be individually
connected to the network and receive its portion of the overall connected to the network and receive its portion of the overall
image from a network-connected video server or video scaler. image from a network-connected video server or video scaler.
Screens are refreshed at 50 or 60 hertz or potentially faster. If Screens are refreshed at 50 or 60 hertz or potentially faster. If
the refresh is not synchronized, the effect of multiple screens the refresh is not synchronized, the effect of multiple screens
acting as one is broken. acting as one is broken.
Networked Audio : Networked loudspeakers, amplifiers and analogue Networked Audio : Networked loudspeakers, amplifiers and analogue I/
I/O devices transmitting or receiving audio signals via RTP can be O devices transmitting or receiving audio signals via RTP can be
connected to various parts of a building or campus network. Such connected to various parts of a building or campus network. Such
situations can for example be found in large conference rooms, situations can for example be found in large conference rooms,
legislative chambers, classrooms (especially those supporting legislative chambers, classrooms (especially those supporting
distance learning) and other large-scale environments such as distance learning) and other large-scale environments such as
stadiums. Since humans are more susceptible to differences in stadiums. Since humans are more susceptible to differences in
audio delay, this use case needs even more accuracy than the video audio delay, this use case needs even more accuracy than the video
wall use case. Depending on the exact application, the need for wall use case. Depending on the exact application, the need for
accuracy can then be in the range of microseconds [1]. accuracy can then be in the range of microseconds [1].
Sensor Arrays : Sensor arrays contain many synchronised measurement Sensor Arrays : Sensor arrays contain many synchronised measurement
skipping to change at page 6, line 30 skipping to change at page 5, line 32
media stream. Source-Specific Media Attributes in the Session media stream. Source-Specific Media Attributes in the Session
Description Protocol (SDP) [RFC5576] defines how source-level Description Protocol (SDP) [RFC5576] defines how source-level
information is included into an SDP session description. information is included into an SDP session description.
traceable time : A clock is considered to provide traceable time if traceable time : A clock is considered to provide traceable time if
it can be proven to be synchronised to International Atomic Time it can be proven to be synchronised to International Atomic Time
(TAI). Coordinated Universal Time (UTC) is a time standard (TAI). Coordinated Universal Time (UTC) is a time standard
synchronized to TAI. UTC is therefore also considered traceable synchronized to TAI. UTC is therefore also considered traceable
time once leap seconds have been taken unto account. GPS time once leap seconds have been taken unto account. GPS
[IS-GPS-200F] is commonly used to provide a TAI traceable time [IS-GPS-200F] is commonly used to provide a TAI traceable time
reference. Some network time synchronisation protocols (e.g. PTP reference. Some network time synchronisation protocols (e.g. PTP
[IEEE1588-2008], NTP) can explicitly indicate that the master [IEEE1588-2008], NTP) can explicitly indicate that the master
clock is providing a traceable time reference over the network. clock is providing a traceable time reference over the network.
4. Timestamp Reference Clock Source Signalling 4. Timestamp Reference Clock Source Signalling
The NTP format timestamps used by RTP are taken by reading a local The NTP format timestamps used by RTP are taken by reading a local
real-time clock at the sender or receiver. This local clock may be real-time clock at the sender or receiver. This local clock may be
synchronised to another clock (time source) by some means or it may synchronised to another clock (time source) by some means or it may
be unsynchronised. A variety of methods are available to synchronise be unsynchronised. A variety of methods are available to synchronise
local clocks to a reference time source, including network time local clocks to a reference time source, including network time
protocols (e.g. NTP [RFC5905], PTP [IEEE1588-2008]) and radio clocks protocols (e.g. NTP [RFC5905], PTP [IEEE1588-2008]) and radio clocks
(e.g. GPS [IS-GPS-200F]). (e.g. GPS [IS-GPS-200F]).
The following sections describe and define SDP signalling, indicating The following sections describe and define SDP signalling, indicating
whether and how the local timestamping clock in an RTP sender/ whether and how the local timestamping clock in an RTP sender/
receiver is synchronised to a reference clock. receiver is synchronised to a reference clock.
4.1. Clock synchronization 4.1. Clock synchronization
Two or more local clocks that are sufficiently synchronised will Two or more local clocks that are sufficiently synchronised will
produce timestamps for a given RTP event can be used as if they came produce timestamps for a given RTP event can be used as if they came
from the same clock. Providing they are sufficiently synchronised, from the same clock. Providing they are sufficiently synchronised,
timestamps produced in one RTP sender or receiver can be directly timestamps produced in one RTP sender or receiver can be directly
compared to a local clock in another RTP sender or receiver. compared to a local clock in another RTP sender or receiver.
The accuracy of synchronisation required is application dependent. The accuracy of synchronisation required is application dependent.
See Applications (Section 2) section for a discussion of applications See Applications (Section 2) section for a discussion of applications
and their corresponding requirements. To serve as a reference clock, and their corresponding requirements. To serve as a reference clock,
clocks must minimally be syntonized (exactly frequency matched) to clocks must minimally be syntonized (exactly frequency matched) to
skipping to change at page 7, line 15 skipping to change at page 6, line 17
timestamps produced in one RTP sender or receiver can be directly timestamps produced in one RTP sender or receiver can be directly
compared to a local clock in another RTP sender or receiver. compared to a local clock in another RTP sender or receiver.
The accuracy of synchronisation required is application dependent. The accuracy of synchronisation required is application dependent.
See Applications (Section 2) section for a discussion of applications See Applications (Section 2) section for a discussion of applications
and their corresponding requirements. To serve as a reference clock, and their corresponding requirements. To serve as a reference clock,
clocks must minimally be syntonized (exactly frequency matched) to clocks must minimally be syntonized (exactly frequency matched) to
one another. one another.
Sufficient synchronisation can typically be achieving by using a Sufficient synchronisation can typically be achieving by using a
network time protocol (e.g. NTP, 802.1AS, IEEE 1588-2008) to network time protocol (e.g. NTP, 802.1AS, IEEE 1588-2008) to
synchronize all devices to a single master clock. synchronize all devices to a single master clock.
Another approach is to use clocks providing a global time reference Another approach is to use clocks providing a global time reference
(e.g. GPS, Galileo). This concept may be used in conjunction with (e.g. GPS, Galileo). This concept may be used in conjunction with
network time protocols as some protocols (e.g. PTP, NTP) allow network time protocols as some protocols (e.g. PTP, NTP) allow master
master clocks to indicate explicitly that they are providing clocks to indicate explicitly that they are providing traceable time.
traceable time.
4.2. Identifying NTP Reference Clocks 4.2. Identifying NTP Reference Clocks
A single NTP server is identified by hostname (or IP address) and an A single NTP server is identified by hostname (or IP address) and an
optional port number. If the port number is not indicated, it is optional port number. If the port number is not indicated, it is
assumed to be the standard NTP port (123). assumed to be the standard NTP port (123).
Two or more NTP servers MAY be listed at the same level in the Two or more NTP servers MAY be listed at the same level in the
session description to indicate that all of the listed servers session description to indicate that all of the listed servers
deliver the same reference time and may be used interchangeably. RTP deliver the same reference time and may be used interchangeably. RTP
skipping to change at page 10, line 40 skipping to change at page 9, line 43
General forms of usage: General forms of usage:
session level: a=ts-refclk:<clksrc> session level: a=ts-refclk:<clksrc>
media level: a=ts-refclk:<clksrc> media level: a=ts-refclk:<clksrc>
source level: a=ssrc:<ssrc-id> ts-refclk:<clksrc> source level: a=ssrc:<ssrc-id> ts-refclk:<clksrc>
ABNF [RFC5234] grammar for the timestamp reference clock attribute: ABNF [RFC5234] grammar for the timestamp reference clock attribute:
; external references:
POS-DIGIT = <See RFC 4566>
token = <See RFC 4566>
byte-string = <See RFC 4566>
DIGIT = <See RFC 5324>
HEXDIG = <See RFC 5324>
CRLF = <See RFC 5324>
hostport = <See RFC 3261, with revisions from RFC 5954>
timestamp-refclk = "ts-refclk:" clksrc CRLF ; external references:
POS-DIGIT = <See RFC 4566>
token = <See RFC 4566>
byte-string = <See RFC 4566>
DIGIT = <See RFC 5324>
HEXDIG = <See RFC 5324>
CRLF = <See RFC 5324>
hostport = <See RFC 3261, with revisions from RFC 5954>
timestamp-refclk = "ts-refclk:" clksrc CRLF
clksrc = ntp / ptp / gps / gal / local / private / clksrc-ext clksrc = ntp / ptp / gps / gal / local / private / clksrc-ext
clksrc-ext = clksrc-param-name clksrc-param-value
clksrc-param-name = token
clksrc-param-value = ["=" byte-string ]
ntp = "ntp=" ntp-server-addr clksrc-ext = clksrc-param-name clksrc-param-value
ntp-server-addr = hostport / "traceable" clksrc-param-name = token
clksrc-param-value = ["=" byte-string ]
ptp = "ptp=" ptp-version ":" ptp-server ntp = "ntp=" ntp-server-addr
ptp-version = "IEEE1588-2002" ntp-server-addr = hostport / "traceable"
/ "IEEE1588-2008"
/ "IEEE802.1AS-2011"
/ ptp-version-ext
ptp-version-ext = token
ptp-server = ptp-gmid [":" ptp-domain] ptp = "ptp=" ptp-version ":" ptp-server
/ "traceable" ptp-version = "IEEE1588-2002"
ptp-gmid = EUI64 / "IEEE1588-2008"
ptp-domain = ptp-domain-name / ptp-domain-nmbr / "IEEE802.1AS-2011"
/ ptp-version-ext
ptp-version-ext = token
; PTP domain allowed characters: 0x21-0x7E (IEEE 1588-2002) ptp-server = ptp-gmid [":" ptp-domain]
ptp-domain-name = "domain-name=" 1*16ptp-domain-char / "traceable"
ptp-domain-char = %x21-7E ptp-gmid = EUI64
ptp-domain = ptp-domain-name / ptp-domain-nmbr
; PTP domain allowed number range: 0-127 (IEEE 1588-2008) ; PTP domain allowed characters: 0x21-0x7E (IEEE 1588-2002)
ptp-domain-nmbr = "domain-nmbr=" ptp-domain-dgts ptp-domain-name = "domain-name=" 1*16ptp-domain-char
ptp-domain-dgts = ptp-domain-n1 / ptp-domain-n2 / ptp-domain-n3 ptp-domain-char = %x21-7E
ptp-domain-n1 = DIGIT ; 0-9
ptp-domain-n2 = POS-DIGIT DIGIT ; 10-99
ptp-domain-n3 = ("10"/"11") DIGIT ; 100-119
/ "12" %x30-37 ; 120-127
gps = "gps" ; PTP domain allowed number range: 0-127 (IEEE 1588-2008)
gal = "gal" ptp-domain-nmbr = "domain-nmbr=" ptp-domain-dgts
local = "local" ptp-domain-dgts = ptp-domain-n1 / ptp-domain-n2 / ptp-domain-n3
private = "private" [ ":traceable" ] ptp-domain-n1 = DIGIT ; 0-9
ptp-domain-n2 = POS-DIGIT DIGIT ; 10-99
ptp-domain-n3 = ("10"/"11") DIGIT ; 100-119
/ "12" %x30-37 ; 120-127
EUI64 = 7(2HEXDIG "-") 2HEXDIG gps = "gps"
gal = "gal"
local = "local"
private = "private" [ ":traceable" ]
EUI64 = 7(2HEXDIG "-") 2HEXDIG
Figure 1: Timestamp Reference Clock Source Signalling Figure 1: Timestamp Reference Clock Source Signalling
4.8.1. Examples 4.8.1. Examples
Figure 2 shows an example SDP description with a timestamp reference Figure 2 shows an example SDP description with a timestamp reference
clock source defined at the session level. clock source defined at the session level.
v=0 v=0
o=jdoe 2890844526 2890842807 IN IP4 192.0.2.1 o=jdoe 2890844526 2890842807 IN IP4 192.0.2.1
s=SDP Seminar s=SDP Seminar
i=A Seminar on the session description protocol i=A Seminar on the session description protocol
u=http://www.example.com/seminars/sdp.pdf u=http://www.example.com/seminars/sdp.pdf
e=j.doe@example.com (Jane Doe) e=j.doe@example.com (Jane Doe)
c=IN IP4 233.252.0.1/64 c=IN IP4 233.252.0.1/64
skipping to change at page 12, line 25 skipping to change at page 11, line 27
m=audio 49170 RTP/AVP 0 m=audio 49170 RTP/AVP 0
m=video 51372 RTP/AVP 99 m=video 51372 RTP/AVP 99
a=rtpmap:99 h263-1998/90000 a=rtpmap:99 h263-1998/90000
Figure 2: Timestamp reference clock definition at the session level Figure 2: Timestamp reference clock definition at the session level
Figure 3 shows an example SDP description with timestamp reference Figure 3 shows an example SDP description with timestamp reference
clock definitions at the media level overriding the session level clock definitions at the media level overriding the session level
defaults. defaults.
v=0 v=0
o=jdoe 2890844526 2890842807 IN IP4 192.0.2.1 o=jdoe 2890844526 2890842807 IN IP4 192.0.2.1
s=SDP Seminar s=SDP Seminar
i=A Seminar on the session description protocol i=A Seminar on the session description protocol
u=http://www.example.com/seminars/sdp.pdf u=http://www.example.com/seminars/sdp.pdf
e=j.doe@example.com (Jane Doe) e=j.doe@example.com (Jane Doe)
c=IN IP4 233.252.0.1/64 c=IN IP4 233.252.0.1/64
t=2873397496 2873404696 t=2873397496 2873404696
a=recvonly a=recvonly
a=ts-refclk:local a=ts-refclk:local
m=audio 49170 RTP/AVP 0 m=audio 49170 RTP/AVP 0
a=ts-refclk:ntp=203.0.113.10 a=ts-refclk:ntp=203.0.113.10
a=ts-refclk:ntp=198.51.100.22 a=ts-refclk:ntp=198.51.100.22
m=video 51372 RTP/AVP 99 m=video 51372 RTP/AVP 99
a=rtpmap:99 h263-1998/90000 a=rtpmap:99 h263-1998/90000
a=ts-refclk:ptp=IEEE802.1AS-2011:39-A7-94-FF-FE-07-CB-D0 a=ts-refclk:ptp=IEEE802.1AS-2011:39-A7-94-FF-FE-07-CB-D0
Figure 3: Timestamp reference clock definition at the media level Figure 3: Timestamp reference clock definition at the media level
Figure 4 shows an example SDP description with a timestamp reference Figure 4 shows an example SDP description with a timestamp reference
clock definition at the source level overriding the session level clock definition at the source level overriding the session level
default. default.
v=0 v=0
o=jdoe 2890844526 2890842807 IN IP4 192.0.2.1 o=jdoe 2890844526 2890842807 IN IP4 192.0.2.1
s=SDP Seminar s=SDP Seminar
skipping to change at page 14, line 7 skipping to change at page 13, line 4
a=mediaclk:sender a=mediaclk:sender
5.2. Direct-Referenced Media Clock 5.2. Direct-Referenced Media Clock
A media clock may be directly derived from a reference clock. For A media clock may be directly derived from a reference clock. For
this case it is required that a reference clock be specified with an this case it is required that a reference clock be specified with an
a=ts-refclk attribute (Section 4.8). a=ts-refclk attribute (Section 4.8).
The signalling optionally indicates a media clock offset value. The The signalling optionally indicates a media clock offset value. The
offset indicates the RTP timestamp value at the epoch (time of offset indicates the RTP timestamp value at the epoch (time of
origin) of the reference clock. If no offset is signalled, the origin) of the reference clock. To use the offset, implementations
offset can be inferred at the receiver by examining RTCP sender need to compute RTP timestamps from reference clocks. To simplify
reports which contain NTP and RTP timestamps which combined define a these calculations, streams utilizing offset signalling SHOULD use a
mapping. Implementations SHOULD use a TAI timestamp reference clock TAI timestamp reference clock to avoid complications introduced by
to avoid complications due to leap seconds. The NTP/RTP timestamp leap seconds. See [I-D.ietf-avtcore-leap-second] for further
mapping provided by RTCP SRs takes precedence over that provided by discussion of leap-second issues in timestamp reference clocks.
the SDP, however the media clock rate implied by the SRs MUST be
consistent with the rate announced in the SDP. To compute the RTP timestamp against an IEEE 1588 (TAI-based)
reference, the time elapsed between the 00:00:00 1 January 1970 IEEE
1588 epoch and the current time must be computed. Between the epoch
and 1 January 2013, there were 15,706 days (including extra days
during leap years). Since there are no leap seconds in a TAI
reference, there are exactly 86,400 seconds during each of these days
or a total of 1,356,998,400 seconds from the epoch to 00:00:00 1
January 2013. A 90 kHz RTP clock for a video stream would have
advanced 122,129,856,000,000 units over this period. With a
signalled offset of 0, the RTP clock value modulo the 32-bit unsigned
representation in the RTP header would have been 2,460,938,240 at
00:00:00 1 January 2013. If an offset of 23,465 had been signalled,
the clock value would have been 2,460,961,705.
In order to use an NTP reference, the actual time elapsed between the
00:00:00, 1 January 1900 NTP epoch to the current time must be
computed. 2,208,988,800 seconds elapsed between the NTP epoch and
00:00:00 1 January 1970 [RFC0868]. Between the beginning of 1970 and
2013, there were 15,706 days elapsed (including extra days during
leap years) and 25 leap seconds inserted. There is therefore a total
of 3,565,987,225 seconds from the NTP epoch to 00:00:00 1 January
2013. A 90 kHz RTP clock for a video stream would have advanced
320,938,850,250,000 units over this period. With a signalled offset
of 0, the RTP clock value modulo the 32-bit unsigned representation
would have been 1,714,023,696 at 00:00:00 1 January 2013.
If no offset is signalled, the offset can be inferred at the receiver
by examining RTCP sender reports which contain NTP and RTP timestamps
which combined define a mapping. The NTP/RTP timestamp mapping
provided by RTCP SRs takes precedence over that singaled through SDP,
however the media clock rate implied by the SRs MUST be consistent
with the rate signalled.
A rate modifier may be specified. The modifier is expressed as the A rate modifier may be specified. The modifier is expressed as the
ratio of two integers and modifies the rate specified or implied by ratio of two integers and modifies the rate specified or implied by
the media description by this ratio. If omitted, the rate is assumed the media description by this ratio. If omitted, the rate is assumed
to be the exact rate specified or implied by the media format. For to be the exact rate specified or implied by the media format. For
example, without a rate specification, the media clock for an 8 kHz example, without a rate specification, the RTP clock for an 8 kHz
G.711 audio stream will advance exactly 8000 units for each second G.711 audio stream will advance exactly 8000 units for each second
advance in the reference clock from which it is derived. advance in the reference clock from which it is derived.
The rate modifier is primarily useful for accommodating certain The rate modifier is primarily useful for accommodating certain
"oddball" audio sample rates associated with NTSC video (see "oddball" audio sample rates associated with NTSC video (see Figure
Figure 7). Modified rates are not advised for video streams which 7). Modified rates are not advised for video streams which generally
generally use a 90 kHz RTP clock regardless of frame rate or sample use a 90 kHz RTP clock regardless of frame rate or sample rate used
rate used for embedded audio. for embedded audio.
a=mediaclk:direct[=<offset>] [rate=<rate numerator>/<rate a=mediaclk:direct[=<offset>] [rate=<rate numerator>/<rate
denominator>] denominator>]
5.3. Stream-Referenced Media Clock 5.3. Stream-Referenced Media Clock
A common synchronisation architecture for audio/visual systems A common synchronisation architecture for audio/visual systems
involves distributing a reference media clock from a master device to involves distributing a reference media clock from a master device to
a number of slave devices, typically by means of a cable. Examples a number of slave devices, typically by means of a cable. Examples
include audio word clock distribution and video black burst include audio word clock distribution and video black burst
skipping to change at page 15, line 44 skipping to change at page 15, line 25
(e.g. internal crystal, audio word clock or video blackburst signal) (e.g. internal crystal, audio word clock or video blackburst signal)
SHOULD tag the stream as a master clock source using the "src:" SHOULD tag the stream as a master clock source using the "src:"
prefix. If master clock identifiers are declared at the media or prefix. If master clock identifiers are declared at the media or
session level, all RTP sources at or below the level of declaration session level, all RTP sources at or below the level of declaration
MUST provide equivalent timing to a slave receiver. MUST provide equivalent timing to a slave receiver.
a=ssrc:<ssrc> mediaclk:id=src:<media-clktag> sender a=ssrc:<ssrc> mediaclk:id=src:<media-clktag> sender
a=mediaclk:id=src:<media-clktag> sender a=mediaclk:id=src:<media-clktag> sender
A transmitted RTP stream slaved to media clock master is signaled by A transmitted RTP stream slaved to media clock master is signalled by
including master clock identifier: including master clock identifier:
a=mediaclk:id=<media-clktag> sender a=mediaclk:id=<media-clktag> sender
An RTP media sender indicates that it is slaved to an IEEE 1722 clock An RTP media sender indicates that it is slaved to an IEEE 1722 clock
master via a stream identifier (an EUI-64): master via a stream identifier (an EUI-64):
a=mediaclk:IEEE1722=<StreamID> a=mediaclk:IEEE1722=<StreamID>
An RTP media sender may gateway IEEE 1722 media clock timing to RTP: An RTP media sender may gateway IEEE 1722 media clock timing to RTP:
skipping to change at page 18, line 19 skipping to change at page 17, line 26
t=0 0 t=0 0
m=audio 5004 RTP/AVP 96 m=audio 5004 RTP/AVP 96
a=rtpmap:96 L24/48000/8 a=rtpmap:96 L24/48000/8
a=sendonly a=sendonly
a=ts-refclk:ptp=IEEE1588-2008:39-A7-94-FF-FE-07-CB-D0:0 a=ts-refclk:ptp=IEEE1588-2008:39-A7-94-FF-FE-07-CB-D0:0
a=mediaclk:direct=963214424 a=mediaclk:direct=963214424
Figure 6: Media clock directly referenced to IEEE 1588-2008 Figure 6: Media clock directly referenced to IEEE 1588-2008
Figure 7 shows an example SDP description 2 channels of 24-bit, 44056 Figure 7 shows an example SDP description 2 channels of 24-bit, 44056
kHz NTSC "pull-down" media clock derived directly from an IEEE 1588- kHz NTSC "pull-down" media clock derived directly from an IEEE
2008 reference clock 1588-2008 reference clock
v=0 v=0
o=- 1311738121 1311738121 IN IP4 192.0.2.1 o=- 1311738121 1311738121 IN IP4 192.0.2.1
c=IN IP4 233.252.0.1/64 c=IN IP4 233.252.0.1/64
s= s=
t=0 0 t=0 0
m=audio 5004 RTP/AVP 96 m=audio 5004 RTP/AVP 96
a=rtpmap:96 L24/44100/2 a=rtpmap:96 L24/44100/2
a=sendonly a=sendonly
a=ts-refclk:ptp=IEEE1588-2008:39-A7-94-FF-FE-07-CB-D0:0 a=ts-refclk:ptp=IEEE1588-2008:39-A7-94-FF-FE-07-CB-D0:0
skipping to change at page 19, line 21 skipping to change at page 18, line 29
a=rtpmap:96 L24/48000/2 a=rtpmap:96 L24/48000/2
a=sendonly a=sendonly
a=ts-refclk:ptp=IEEE1588-2008:39-A7-94-FF-FE-07-CB-D0:0 a=ts-refclk:ptp=IEEE1588-2008:39-A7-94-FF-FE-07-CB-D0:0
a=mediaclk:IEEE1722=38-D6-6D-8E-D2-78-13-2F a=mediaclk:IEEE1722=38-D6-6D-8E-D2-78-13-2F
Figure 9: RTP stream with media clock slaved to an IEEE1722 master Figure 9: RTP stream with media clock slaved to an IEEE1722 master
device device
6. Signalling Considerations 6. Signalling Considerations
Signaling of timestamp reference clock source (Section 4.8) and media Signalling of timestamp reference clock source (Section 4.8) and
clock source (Section 5.4) is defined to be used either by media clock source (Section 5.4) is defined to be used either by
applications that implement the SDP Offer/Answer model [RFC3264] or applications that implement the SDP Offer/Answer model [RFC3264] or
by applications that use SDP to describe media and transport by applications that use SDP to describe media and transport
configurations. configurations.
A description SHOULD include both reference clock signalling and A description SHOULD include both reference clock signalling and
media clock signalling. If no reference clock is available, this media clock signalling. If no reference clock is available, this
SHOULD be signalled as a local reference (Section 4.6). SHOULD be signalled as a local reference (Section 4.6).
When no media clock signalling is present, an asynchronous media When no media clock signalling is present, an asynchronous media
clock (Section 5.1) MUST be assumed. When no reference clock clock (Section 5.1) MUST be assumed. When no reference clock
skipping to change at page 20, line 6 skipping to change at page 19, line 14
6.1. Usage in Offer/Answer 6.1. Usage in Offer/Answer
During offer/answer, clock source signalling via SDP uses a During offer/answer, clock source signalling via SDP uses a
declarative model. Supported media and/or reference clocks are declarative model. Supported media and/or reference clocks are
specified in the offered SDP description. The answerer may accept or specified in the offered SDP description. The answerer may accept or
reject the offer in an application-specific way depending on the reject the offer in an application-specific way depending on the
clocks that are available and the clocks that are offered. For clocks that are available and the clocks that are offered. For
example, an answerer may choose to accept an offer that lacks a example, an answerer may choose to accept an offer that lacks a
common clock by falling back to a lower performance mode of operation common clock by falling back to a lower performance mode of operation
(e.g. by assuming reference or media clocks are local rather than (e.g. by assuming reference or media clocks are local rather than
shared). Conversely, the answerer may choose to reject the offer shared). Conversely, the answerer may choose to reject the offer
when the offered clock specifications indicate that the available when the offered clock specifications indicate that the available
reference and/or media clocks are incompatible. reference and/or media clocks are incompatible.
While negotiation of reference clock and media clock attributes is While negotiation of reference clock and media clock attributes is
not defined in this document, negotiation MAY be accomplished using not defined in this document, negotiation MAY be accomplished using
the capabilities negotiation procedures defined in [RFC5939]. the capabilities negotiation procedures defined in [RFC5939].
6.1.1. Indicating Support for Clock Source Signalling 6.1.1. Indicating Support for Clock Source Signalling
skipping to change at page 21, line 15 skipping to change at page 20, line 22
6.2. Usage Outside of Offer/Answer 6.2. Usage Outside of Offer/Answer
SDP can be employed outside of the Offer/Answer context, for instance SDP can be employed outside of the Offer/Answer context, for instance
for multimedia sessions that are announced through the Session for multimedia sessions that are announced through the Session
Announcement Protocol (SAP) [RFC2974], or streamed through the Real Announcement Protocol (SAP) [RFC2974], or streamed through the Real
Time Streaming Protocol (RTSP) [RFC2326]. Time Streaming Protocol (RTSP) [RFC2326].
Devices using published descriptions to join sessions SHOULD assess Devices using published descriptions to join sessions SHOULD assess
their synchronization compatibility with the described session based their synchronization compatibility with the described session based
on the clock source signaling and SHOULD NOT attempt to join a on the clock source signalling and SHOULD NOT attempt to join a
session with incompatible reference or media clocks. session with incompatible reference or media clocks.
7. Security Considerations 7. Security Considerations
Entities receiving and acting upon an SDP message SHOULD be aware Entities receiving and acting upon an SDP message SHOULD be aware
that a session description cannot be trusted unless it has been that a session description cannot be trusted unless it has been
obtained by an authenticated transport protocol from a known and obtained by an authenticated transport protocol from a known and
trusted source. Many different transport protocols may be used to trusted source. Many different transport protocols may be used to
distribute session description, and the nature of the authentication distribute session description, and the nature of the authentication
will differ from transport to transport. For some transports, will differ from transport to transport. For some transports,
skipping to change at page 24, line 39 skipping to change at page 23, line 39
associated with the token (mediaclock-param-value) associated with the token (mediaclock-param-value)
Initial values for the Media Clock Source Parameters registry are Initial values for the Media Clock Source Parameters registry are
given below. given below.
Future assignments are to be made through the Specification Required Future assignments are to be made through the Specification Required
policy [RFC5226]. The Name field in the table corresponds to a new policy [RFC5226]. The Name field in the table corresponds to a new
value corresponding to mediaclock-param-name. The Reference must value corresponding to mediaclock-param-name. The Reference must
specify a syntax corresponding to mediaclock-param-value. specify a syntax corresponding to mediaclock-param-value.
+----------+--------------------------------+-----------------------+ +-------------+---------------------------------+-------------------+
| Name | Long Name | Reference | | Name | Long Name | Reference |
+----------+--------------------------------+-----------------------+ +-------------+---------------------------------+-------------------+
| sender | Asynchronously Generated Media | This document, | | sender | Asynchronously Generated Media | This document, |
| | Clock | section 5 | | | Clock | section 5 |
| direct | Direct-Referenced Media Clock | This document, | | direct | Direct-Referenced Media Clock | This document, |
| | | section 5 | | | | section 5 |
| IEEE1722 | IEEE1722 Media Stream | This document, | | IEEE1722 | IEEE1722 Media Stream | This document, |
| | Identifier | section 5 | | | Identifier | section 5 |
+----------+--------------------------------+-----------------------+ +-------------+---------------------------------+-------------------+
8.5. Source-level Attributes 8.5. Source-level Attributes
[RFC5576] requires new source-level attributes to be registered with [RFC5576] requires new source-level attributes to be registered with
the IANA registry named "att-field (source level)". the IANA registry named "att-field (source level)".
8.5.1. Source-level Timestamp Reference Clock Attribute 8.5.1. Source-level Timestamp Reference Clock Attribute
The source-level SDP attribute "ts-refclk" defined by this document The source-level SDP attribute "ts-refclk" defined by this document
is registered with the "att-field (source level)" IANA registry of is registered with the "att-field (source level)" IANA registry of
SDP Parameters according to Figure 10. SDP Parameters according to Figure 10.
8.5.2. Source-level Media Clock Attribute 8.5.2. Source-level Media Clock Attribute
The source-level SDP attribute "mediaclk" defined by this document is The source-level SDP attribute "mediaclk" defined by this document is
registered with the "att-field (source level)" IANA registry of SDP registered with the "att-field (source level)" IANA registry of SDP
Parameters according to Figure 11. Parameters according to Figure 11.
9. References 9. Acknowledgements
9.1. Normative References The authors would like to thank Magnus Westerlund and Paul Kyzivat
for valuable comments which resulted in important improvements to
this document.
10. References
10.1. Normative References
[I-D.ietf-avtcore-6222bis] [I-D.ietf-avtcore-6222bis]
Begen, A., Perkins, C., Wing, D., and E. Rescorla, Begen, A., Perkins, C., Wing, D., and E. Rescorla,
"Guidelines for Choosing RTP Control Protocol (RTCP) "Guidelines for Choosing RTP Control Protocol (RTCP)
Canonical Names (CNAMEs)", draft-ietf-avtcore-6222bis-06 Canonical Names (CNAMEs)", draft-ietf-avtcore-6222bis-06
(work in progress), July 2013. (work in progress), July 2013.
[IEEE1588-2002] [IEEE1588-2002]
Institute of Electrical and Electronics Engineers, "1588- Institute of Electrical and Electronics Engineers,
2002 - IEEE Standard for a Precision Clock Synchronization "1588-2002 - IEEE Standard for a Precision Clock
Protocol for Networked Measurement and Control Systems", Synchronization Protocol for Networked Measurement and
IEEE Std 1588-2002, 2002, <http://standards.ieee.org/ Control Systems", IEEE Std 1588-2002, 2002, <http://
findstds/standard/1588-2002.html>. standards.ieee.org/findstds/standard/1588-2002.html>.
[IEEE1588-2008] [IEEE1588-2008]
Institute of Electrical and Electronics Engineers, "1588- Institute of Electrical and Electronics Engineers,
2008 - IEEE Standard for a Precision Clock Synchronization "1588-2008 - IEEE Standard for a Precision Clock
Protocol for Networked Measurement and Control Systems", Synchronization Protocol for Networked Measurement and
IEEE Std 1588-2008, 2008, <http://standards.ieee.org/ Control Systems", IEEE Std 1588-2008, 2008, <http://
findstds/standard/1588-2008.html>. standards.ieee.org/findstds/standard/1588-2008.html>.
[IEEE1722] [IEEE1722]
Institute of Electrical and Electronics Engineers, "IEEE Institute of Electrical and Electronics Engineers, "IEEE
Standard for Layer 2 Transport Protocol for Time Sensitive Standard for Layer 2 Transport Protocol for Time Sensitive
Applications in a Bridged Local Area Network", <http:// Applications in a Bridged Local Area Network", , <http://
standards.ieee.org/findstds/standard/1722-2011.html>. standards.ieee.org/findstds/standard/1722-2011.html>.
[IEEE802.1AS-2011] [IEEE802.1AS-2011]
Institute of Electrical and Electronics Engineers, "Timing Institute of Electrical and Electronics Engineers, "Timing
and Synchronization for Time-Sensitive Applications in and Synchronization for Time-Sensitive Applications in
Bridged Local Area Networks", <http://standards.ieee.org/ Bridged Local Area Networks", , <http://standards.ieee.org
findstds/standard/802.1AS-2011.html>. /findstds/standard/802.1AS-2011.html>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
with Session Description Protocol (SDP)", RFC 3264, with Session Description Protocol (SDP)", RFC 3264, June
June 2002. 2002.
[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, July 2006. Description Protocol", RFC 4566, July 2006.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226, IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008. May 2008.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008. Specifications: ABNF", STD 68, RFC 5234, January 2008.
skipping to change at page 26, line 43 skipping to change at page 26, line 5
Time Protocol Version 4: Protocol and Algorithms Time Protocol Version 4: Protocol and Algorithms
Specification", RFC 5905, June 2010. Specification", RFC 5905, June 2010.
[RFC6051] Perkins, C. and T. Schierl, "Rapid Synchronisation of RTP [RFC6051] Perkins, C. and T. Schierl, "Rapid Synchronisation of RTP
Flows", RFC 6051, November 2010. Flows", RFC 6051, November 2010.
[RFC6222] Begen, A., Perkins, C., and D. Wing, "Guidelines for [RFC6222] Begen, A., Perkins, C., and D. Wing, "Guidelines for
Choosing RTP Control Protocol (RTCP) Canonical Names Choosing RTP Control Protocol (RTCP) Canonical Names
(CNAMEs)", RFC 6222, April 2011. (CNAMEs)", RFC 6222, April 2011.
9.2. Informative References 10.2. Informative References
[AES11-2009] [AES11-2009]
Audio Engineering Society, "AES11-2009: AES recommended Audio Engineering Society, "AES11-2009: AES recommended
practice for digital audio engineering - Synchronization practice for digital audio engineering - Synchronization
of digital audio equipment in studio operations", of digital audio equipment in studio operations", ,
<http://www.aes.org/standards/>. <http://www.aes.org/standards/>.
[I-D.ietf-avtcore-idms] [I-D.ietf-avtcore-idms]
Brandenburg, R., Stokking, H., Deventer, O., Boronat, F., Brandenburg, R., Stokking, H., Deventer, O., Boronat, F.,
Montagud, M., and K. Gross, "Inter-destination Media Montagud, M., and K. Gross, "Inter-destination Media
Synchronization using the RTP Control Protocol (RTCP)", Synchronization using the RTP Control Protocol (RTCP)",
draft-ietf-avtcore-idms-12 (work in progress), July 2013. draft-ietf-avtcore-idms-13 (work in progress), August
2013.
[I-D.ietf-avtcore-leap-second]
Gross, K. and R. Brandenburg, "RTP and Leap Seconds",
draft-ietf-avtcore-leap-second-05 (work in progress),
October 2013.
[IEEE802.1BA-2011] [IEEE802.1BA-2011]
Institute of Electrical and Electronics Engineers, "Audio Institute of Electrical and Electronics Engineers, "Audio
Video Bridging (AVB) Systems", <http://standards.ieee.org/ Video Bridging (AVB) Systems", , <http://
findstds/standard/802.1BA-2011.html>. standards.ieee.org/findstds/standard/802.1BA-2011.html>.
[IS-GPS-200F] [IS-GPS-200F]
Global Positioning Systems Directorate, "Navstar GPS Space Global Positioning Systems Directorate, "Navstar GPS Space
Segment/Navigation User Segment Interfaces", Segment/Navigation User Segment Interfaces", September
September 2011. 2011.
[RFC0868] Postel, J. and K. Harrenstien, "Time Protocol", STD 26,
RFC 868, May 1983.
[RFC2326] Schulzrinne, H., Rao, A., and R. Lanphier, "Real Time [RFC2326] Schulzrinne, H., Rao, A., and R. Lanphier, "Real Time
Streaming Protocol (RTSP)", RFC 2326, April 1998. Streaming Protocol (RTSP)", RFC 2326, April 1998.
[RFC2974] Handley, M., Perkins, C., and E. Whelan, "Session [RFC2974] Handley, M., Perkins, C., and E. Whelan, "Session
Announcement Protocol", RFC 2974, October 2000. Announcement Protocol", RFC 2974, October 2000.
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E. A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261, Schooler, "SIP: Session Initiation Protocol", RFC 3261,
June 2002. June 2002.
[RFC5939] Andreasen, F., "Session Description Protocol (SDP) [RFC5939] Andreasen, F., "Session Description Protocol (SDP)
Capability Negotiation", RFC 5939, September 2010. Capability Negotiation", RFC 5939, September 2010.
[SMPTE-318-1999] [SMPTE-318-1999]
Society of Motion Picture & Television Engineers, Society of Motion Picture & Television Engineers,
"Television and Audio - Synchronization of 59.94- or 50-Hz "Television and Audio - Synchronization of 59.94- or 50-Hz
Related Video and Audio Systems in Analog and Digital Related Video and Audio Systems in Analog and Digital
Areas - Reference Signals", <http://standards.smpte.org/>. Areas - Reference Signals", ,
<http://standards.smpte.org/>.
URIs
[1] <http://www.ieee802.org/1/files/public/docs2007/
as-dolsen-time-accuracy-0407.pdf>
Authors' Addresses Authors' Addresses
Aidan Williams Aidan Williams
Audinate Audinate
Level 1, 458 Wattle St Level 1, 458 Wattle St
Ultimo, NSW 2007 Ultimo, NSW 2007
Australia Australia
Phone: +61 2 8090 1000 Phone: +61 2 8090 1000
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