draft-ietf-avt-rapid-rtp-sync-03.txt | draft-ietf-avt-rapid-rtp-sync-04.txt | |||
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Network Working Group C. Perkins | Network Working Group C. Perkins | |||
Internet-Draft University of Glasgow | Internet-Draft University of Glasgow | |||
Updates: RFC3550 T. Schierl | Updates: RFC3550 T. Schierl | |||
(if approved) Fraunhofer HHI | (if approved) Fraunhofer HHI | |||
Intended status: Standards Track June 30, 2009 | Intended status: Standards Track July 3, 2009 | |||
Expires: January 1, 2010 | Expires: January 4, 2010 | |||
Rapid Synchronisation of RTP Flows | Rapid Synchronisation of RTP Flows | |||
draft-ietf-avt-rapid-rtp-sync-03.txt | draft-ietf-avt-rapid-rtp-sync-04.txt | |||
Status of this Memo | Status of this Memo | |||
This Internet-Draft is submitted to IETF in full conformance with the | This Internet-Draft is submitted to IETF 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 | |||
Task Force (IETF), its areas, and its working groups. Note that | Task Force (IETF), its areas, and its working groups. Note that | |||
other groups may also distribute working documents as Internet- | other groups may also distribute working documents as Internet- | |||
Drafts. | Drafts. | |||
skipping to change at page 1, line 34 ¶ | skipping to change at page 1, line 34 ¶ | |||
and may be updated, replaced, or obsoleted by other documents at any | and may be updated, replaced, or obsoleted by other documents at any | |||
time. It is inappropriate to use Internet-Drafts as reference | time. It is inappropriate to use Internet-Drafts as reference | |||
material or to cite them other than as "work in progress." | material or to cite them other than as "work in progress." | |||
The list of current Internet-Drafts can be accessed at | The list of current Internet-Drafts can be accessed at | |||
http://www.ietf.org/ietf/1id-abstracts.txt. | http://www.ietf.org/ietf/1id-abstracts.txt. | |||
The list of Internet-Draft Shadow Directories can be accessed at | The list of Internet-Draft Shadow Directories can be accessed at | |||
http://www.ietf.org/shadow.html. | http://www.ietf.org/shadow.html. | |||
This Internet-Draft will expire on January 1, 2010. | This Internet-Draft will expire on January 4, 2010. | |||
Copyright Notice | Copyright Notice | |||
Copyright (c) 2009 IETF Trust and the persons identified as the | Copyright (c) 2009 IETF Trust and the persons identified as the | |||
document authors. All rights reserved. | document authors. All rights reserved. | |||
This document is subject to BCP 78 and the IETF Trust's Legal | This document is subject to BCP 78 and the IETF Trust's Legal | |||
Provisions Relating to IETF Documents in effect on the date of | Provisions Relating to IETF Documents in effect on the date of | |||
publication of this document (http://trustee.ietf.org/license-info). | publication of this document (http://trustee.ietf.org/license-info). | |||
Please review these documents carefully, as they describe your rights | Please review these documents carefully, as they describe your rights | |||
skipping to change at page 5, line 14 ¶ | skipping to change at page 5, line 14 ¶ | |||
2. Synchronisation of RTP Flows | 2. Synchronisation of RTP Flows | |||
RTP flows are synchronised by receivers based on information that is | RTP flows are synchronised by receivers based on information that is | |||
contained in RTCP SR packets generated by senders (specifically, the | contained in RTCP SR packets generated by senders (specifically, the | |||
NTP-format timestamp and the RTP timestamp). Synchronisation | NTP-format timestamp and the RTP timestamp). Synchronisation | |||
requires that a common reference clock MUST be used to generate the | requires that a common reference clock MUST be used to generate the | |||
NTP-format timestamps in a set of flows that are to be synchronised. | NTP-format timestamps in a set of flows that are to be synchronised. | |||
Furthermore, to achieve more rapid and accurate synchronisation, it | Furthermore, to achieve more rapid and accurate synchronisation, it | |||
is RECOMMENDED that senders and receivers use a common reference | is RECOMMENDED that senders and receivers use a common reference | |||
clock where possible (recognising that this is often not possible | clock with common properties, especially timebase, where possible | |||
when RTP is used outside of controlled environments); the means by | (recognising that this is often not possible when RTP is used outside | |||
which that common reference clock is distributed are outside the | of controlled environments); the means by which that common reference | |||
clock and its properties are signalled and distributed is outside the | ||||
scope of this memo. | scope of this memo. | |||
For multimedia sessions, each type of media (e.g. audio or video) is | For multimedia sessions, each type of media (e.g. audio or video) is | |||
sent in a separate RTP session, and the receiver associates RTP flows | sent in a separate RTP session, and the receiver associates RTP flows | |||
to be synchronised by means of the canonical end-point identifier | to be synchronised by means of the canonical end-point identifier | |||
(CNAME) item included in the RTCP Source Description (SDES) packets | (CNAME) item included in the RTCP Source Description (SDES) packets | |||
generated by the sender or signalled out of band [10]. For layered | generated by the sender or signalled out of band [10]. For layered | |||
media, different layers can be sent in different RTP sessions, or | media, different layers can be sent in different RTP sessions, or | |||
using different SSRC values within a single RTP session; in both | using different SSRC values within a single RTP session; in both | |||
cases, the CNAME is used to identify flows to be synchronised. To | cases, the CNAME is used to identify flows to be synchronised. To | |||
End of changes. 4 change blocks. | ||||
7 lines changed or deleted | 8 lines changed or added | |||
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