Network Working Group I. Johansson Internet-Draft B. Burman Intended status: Standards Track Ericsson AB Expires: April 28, 2011 Oct 25, 2010 Simultaneous Media Grouping draft-johansson-mmusic-grouping-simultaneous-01 Abstract This document proposes an extension to the grouping framework [RFC5888]. The extension identifies media descriptions that contain different representations of identical content. An example of this is an endpoint that sends both a high-resolution and a low-resolution video sequence to a conferencing server. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on April 28, 2011. Copyright Notice Copyright (c) 2010 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of Johansson & Burman Expires April 28, 2011 [Page 1] Internet-Draft Simultaneous Media Grouping Oct 2010 publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Description . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3.1. Preference . . . . . . . . . . . . . . . . . . . . . . . . 3 3.2. Example . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5 7.1. Normative References . . . . . . . . . . . . . . . . . . . 5 7.2. Informative References . . . . . . . . . . . . . . . . . . 5 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 5 Johansson & Burman Expires April 28, 2011 [Page 2] Internet-Draft Simultaneous Media Grouping Oct 2010 1. Definitions This document uses the following acronyms and definitions frequently: MCU : Multipoint Control Unit SID : Simultaneous (stream) Identity 2. Introduction Advanced multipoint teleconferencing solutions often makes use of an MCU to determine which video should be transmitted to the users. In order to avoid transcoding in the MCU it is popular to encode at least two versions of the same media in each endpoint. One example is a main video stream with high resolution and one secondary stream with low resolution. The MCU can then decide to distribute the high resolution stream of the active talker to the other participants. Optionally, the MCU may choose to distribute the lower resolution stream to receivers that do not have sufficient capability to receive the high resolution stream of the active talker. Another optional use of low resolution streams is to distribute non-active talkers media, in addition to a high resolution version of the active talker. Draft [RFC5888] updates the basic grouping mechanism. It defines the LS and FID semantics tags, LS is used for lip synchronization and FID for flow identification. It would be tempting to use the FID tag for the above purpose, this is however explicitly forbidden in [RFC5888]. The SDP Content Attribute [RFC4796] would be another grouping technique candidate, but the currently defined semantics of values "main" and "alt" is not a good match to the scope of this draft. For this reason a new semantics-extension token SID is defined as extension to [RFC5888]. 3. Description The token SID is defined as semantics-extension to [RFC5888]. This token identifies media descriptors that carry the same media encoded with different bitrates or codecs. 3.1. Preference In this use the identification-tags (defined in [RFC5888]) indicate the preference for the media carried by the media descriptors in such a way that a lower number has preference over a higher number. This Johansson & Burman Expires April 28, 2011 [Page 3] Internet-Draft Simultaneous Media Grouping Oct 2010 way it becomes natural for a receiver to know which media is most preferred (or has the highest quality), even if that information could be extracted from other SDP attributes and (possibly codec specific) parameters. 3.2. Example An SDP simple example to highlight the use for the new token. a=group: SID 1 2 3 m=video 52738 RTP/AVP 99 i=Large size 1280x720 send-only video a=mid:1 a=rtpmap:99 H264/90000 a=fmtp:99 profile-level-id=4DC01F; \ sprop-parameter-sets= Z0LAH5ZkAoAt0IAAAAMAgAAAHkeMGVA=,aM48gA== b=AS:1000 a=sendonly m=video 52740 RTP/AVP 100 i=Medium size 640x360 send-only video a=mid:2 a=rtpmap:100 H264/90000 a=fmtp:100 profile-level-id=4DC016; \ sprop-parameter-sets= Z0LAHpZkBQF/ywgAAAMACAAAAwHkeLF1,aM48gA== b=AS:350 a=sendonly m=video 52742 RTP/AVP 101 i=Small size 256x144 send-only video a=mid:3 a=rtpmap:101 H264/90000 a=fmtp:101 profile-level-id=42C00B; \ sprop-parameter-sets= Z0LADJZkCAnQgAAAAwCAAAAeR4oVUA==,aM48gA== b=AS:128 a=sendonly Three streams are offered (sendonly), each stream is a representation of a common recording (for instance a camera in a conference room). To indicate for the end user that the three streams carry identical media the new token 'SID' is used. 4. IANA Considerations The following contact information shall be used for all registrations in this document: Johansson & Burman Expires April 28, 2011 [Page 4] Internet-Draft Simultaneous Media Grouping Oct 2010 Ingemar Johansson ingemar.s.johansson@ericsson.com Laboratoriegrand 11 971 28 Lulea Sweden Note to the RFC Editor: In the following, please replace "XXXX" with the number of this document prior to publication as an RFC. The IANA is requested to register the following token as semantics- extension to the group attribute in [RFC5888]. Semantics Token Reference ------------------------------- ----- --------- Simultaneous stream Identifier SID RFCXXXX 5. Security Considerations T.B.D 6. Acknowledgements T.B.D 7. References 7.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC5888] Camarillo, G. and H. Schulzrinne, "The Session Description Protocol (SDP) Grouping Framework", RFC 5888, June 2010. 7.2. Informative References [RFC4796] Hautakorpi, J. and G. Camarillo, "The Session Description Protocol (SDP) Content Attribute", RFC 4796, February 2007. Johansson & Burman Expires April 28, 2011 [Page 5] Internet-Draft Simultaneous Media Grouping Oct 2010 Authors' Addresses Ingemar Johansson Ericsson AB Laboratoriegrand 11 SE-971 28 Lulea SWEDEN Phone: +46 73 0783289 Email: ingemar.s.johansson@ericsson.com Bo Burman Ericsson AB Farogatan 6 SE-164 80 Kista Sweden Phone: +46 10 7141311 Email: bo.burman@ericsson.com Johansson & Burman Expires April 28, 2011 [Page 6]