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Versions: (draft-overlay-grouping) 00 draft-abhishek-mmusic-superimposition-grouping

mmusic                                                       R. Abhishek
Internet-Draft                                                   Tencent
Intended status: Standards Track                        October 27, 2020
Expires: April 30, 2021


SDP Overlay Grouping framework for immersive telepresence media streams
               draft-abhishek-mmusic-overlay-grouping-00

Abstract

   This document defines semantics that allow for signalling a new SDP
   group "OL" for overlays in an immersive telepresence session.  The
   "OL" attribute can be used by the application to relate all the
   overlay media streams enabling them to be added as overlay on top of
   the immersive video.  The overlay grouping semantics is required, if
   the media data is seperate and transported via different protocols.

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
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   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 30, 2021.

Copyright Notice

   Copyright (c) 2020 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
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   include Simplified BSD License text as described in Section 4.e of




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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Contribution and Discussion Venues for this draft . . . . . .   3
   3.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Overview of Operation . . . . . . . . . . . . . . . . . . . .   3
   5.  Overlay Stream Group Identification Attribute . . . . . . . .   4
   6.  Use of group and mid  . . . . . . . . . . . . . . . . . . . .   4
   7.  Example of OL . . . . . . . . . . . . . . . . . . . . . . . .   5
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   7
     10.2.  Informative References . . . . . . . . . . . . . . . . .   8
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   Telepresence [RFC7205] can be described as a technology that allows a
   person the experience of "being present" at a remote location for
   video as well as audio telepresence sessions, so as to enable the
   users sense of realism and presence [TS26.223] .  SDP [RFC4566] is
   being predominantly used for describing the format for multimedia
   communication session for telepresence conferencing.  These use open
   standards such as RTP [RFC3550] and SIP [RFC3261] .

   An SDP session may contain more than one media lines with each media
   line identified by "m"=line.  Each line denotes a single media
   stream.  If multiple media lines are present in a session, a receiver
   needs to identify relationship between those media lines.

   Overlay media stream can be defined as a piece of visual media which
   can be rendered over an immersive video or image or over a viewport
   [ISO23090] . When an overlay is transmitted, its media stream needs
   to be uniquely identified across multiple SDP descriptions exchanged
   with different receivers so that the streams can be identified in
   terms of its role in the session irrespective of its media type and
   transport protocol.

   In an immersive telepresence session, one media is streamed as an
   immersive stream whereas other media streams are overlaid on top of
   the immersive video/image.  An end user can stream more than one
   overlay, subject to its decoding capacity.  When multiple overlay
   streams are transmitted within a session, the end application upon
   receiving, needs to be able to relate the media streams to each



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   other.  This can be achieved by SDP grouping framework by using the
   "group" attribute that groups different "m" lines in a session.
   However, the current SDP signalling framework does not provide such
   grouping semantics for overlays.

   This document describes a new SDP group semantics for grouping the
   overlays when an immersive media stream is transmitted for
   telepresence conferencing.  SDP session description consists of one
   or multiple media lines know as "m" lines which can be identified by
   a token carried in a "mid" attribute.  The SDP session describes a
   session-level group level attributes that groups different media
   lines using a defined group semantics.  The semantics defined in this
   memo is to be used in conjuction with [RFC5888] titled "The Session
   Description Protocol (SDP) Grouping Framework".

2.  Contribution and Discussion Venues for this draft

   (Note to RFC Editor - if this document ever reaches you, please
   remove this section)

   Substantial discussion of this document should take place on the
   MMUSIC working group mailing list ( mmusic@ietf.org).  Subscription
   and archive details are at https://www.ietf.org/mailman/listinfo/
   mmusic.

3.  Terminology

   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 [RFC2119].

4.  Overview of Operation

   A non-normative description of SDP overlay group semantics is
   described in this section.  An immersive stream for a telepresence
   session may consist of one or more conference rooms with a 360-degree
   camera and the remote users using head mounted display for streaming.
   "Participant cameras" are used to capture the conference participants
   whereas "presentation cameras" or "content cameras" can be used for
   document display [RFC7205] .  The remote participant can stream any
   of the available immersive video in the session as background whereas
   other available streams such as the presentation stream or 2D video
   from any other room or participant can be used as an overlay on top
   of the immersive video/image.

   A user with a head mounted display may stream more than one overlay
   in a single SDP session.  These overlay streams are transmitted via
   "m" line in SDP session description.  Each "m" line in the session



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   description is identified by a token carried via the "mid" attribute.
   When multiple overlay streams are transmitted within a session, the
   end application upon receiving, needs to be able to relate the media
   streams to each other.  This is achieved by using the SDP grouping
   framework [RFC5888].  The session descriptions carries session-level
   "group" attribute for the overlays which groups different "m" lines
   using overlay(OL) group semantics.

5.  Overlay Stream Group Identification Attribute

   The "overlay media stream identification" attribute is used to
   identify overlay media streams within a session description.  In a
   overlay group, the media lines MAY have different media contents.
   Its formatting in SDP [RFC4566] is described by the following
   Augmented Backus-Naur Form (ABNF) [RFC5234] :

   mid-attribute = "a=mid:" identification-tag
   identification-tag = token
                        ; token is defined in RFC4566

   This documents defines a new group semantics "OL" identification
   media attribute, which is used to identify overlay group media
   streams within a session description.  It is used for grouping the
   media streams for different overlays together within a session.  An
   application that receives a session description that contains "m"
   lines grouped together using "OL" semantics MUST overlay the
   corresponding media streams on top of the immersive media stream.

6.  Use of group and mid

   All group and mid attributes MUST follow the rules defined in
   [RFC5888].  The "mid" attribute should be used for all "m" lines
   within a session description . If for any "m" lines within a session,
   no "mid" attribute is identified for a session description, the
   application MUST NOT perform any media line grouping.  If the
   identification-tags associated with "a=group" lines do not map to any
   "m" lines, it MUST be ignored.

   group-attribute ="a=group:" semantics
                     *(SP identification-tag)
   semantics = "OL" / semantics-extension
   semantics-extension = token
                         ; token is defined in RFC4566








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7.  Example of OL

   The following two examples show a session description for overlays in
   an immersive telepresence conference.  The "group" line indicates
   that the "m" lines with tokens 1 and 2 are grouped for the purpose of
   overlays and intended to be overlaid on top of the immersive video.

   In the first example shown below, two overlays are being transmitted.
   The first media stream (mid:1) carries the video stream, and the
   second stream (mid:2) contains an audio stream.

       v=0
       o=Alice 292742730 29277831 IN IP4 233.252.0.74
       c=IN IP4 233.252.0.79
       t=0 0
       a=group:OL 1 2
       m=video 30000 RTP/AVP 31
       a=mid:1
       m=audio 30002 RTP/AVP 31
       a=mid:2

   The second example, below, uses 'content' attribute with the media
   streams which are transmitted for overlay purpose.

       v=0
       o=Alice 292742730 29277831 IN IP4 233.252.0.74
       c=IN IP4 233.252.0.79
       t=0 0
       a=group:OL 1 2
       m=video 30000 RTP/AVP 31
       a= content:slides
       a=mid:1
       m=video 30002 RTP/AVP 31
       a=content:speaker
       a=mid:2

8.  Security Considerations

   All security considerations as defined in [RFC5888] apply:

   Using the "group" parameter with FID semantics, an entity that
   managed to modify the session descriptions exchanged between the
   participants to establish a multimedia session could force the
   participants to send a copy of the media to any destination of its
   choosing.

   Integrity mechanisms provided by protocols used to exchange session
   descriptions and media encryption can be used to prevent this attack.



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   In SIP, Secure/Multipurpose Internet Mail Extensions (S/MIME)
   [RFC8550] and Transport Layer Security (TLS) [RFC8446] can be used to
   protect session description exchanges in an end-to-end and a hop-
   byhop fashion, respectively.

9.  IANA Considerations

   The following contact information shall be used for all registrations
   included here:

   Contact:         Rohit Abhishek
                    email: rabhishek@rabhishek.com
                    tel  : +1-816-585-7500

   This document defines a new SDP group semantics for overlays for a
   immersive telepresence session.  This attribute can be used by the
   application to group all the overlays in a session.  Semantics values
   to be used with this framework should be registered by the IANA
   following the Standards Action policy [RFC8126].  This document adds
   a new group semantics and follows the registry group defined in
   [RFC5888].

   The following semantics needs to be registered by IANA in Semantics
   for the "group" SDP Attribute under SDP Parameters.

   Semantics             Token          Reference
   ----------------------------------------------
   Overlay               OL              RFCXXXX

   The "OL" attribute is used to group different media streams to be
   rendered as overlays.  Its format is defined in Section 5 .

   The IANA Considerations section of the RFC MUST include the following
   information, which appears in the IANA registry along with the RFC
   number of the publication.

   o  A brief description of the semantics.

   o  Token to be used within the "group" attribute.  This token may be
      of any length, but SHOULD be no more than four characters long.

   o  Reference to a standards track RFC.

10.  References







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10.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC3261]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
              A., Peterson, J., Sparks, R., Handley, M., and E.
              Schooler, "SIP: Session Initiation Protocol", RFC 3261,
              DOI 10.17487/RFC3261, June 2002,
              <https://www.rfc-editor.org/info/rfc3261>.

   [RFC3550]  Schulzrinne, H., Casner, S., Frederick, R., and V.
              Jacobson, "RTP: A Transport Protocol for Real-Time
              Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550,
              July 2003, <https://www.rfc-editor.org/info/rfc3550>.

   [RFC4566]  Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
              Description Protocol", RFC 4566, DOI 10.17487/RFC4566,
              July 2006, <https://www.rfc-editor.org/info/rfc4566>.

   [RFC5234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234,
              DOI 10.17487/RFC5234, January 2008,
              <https://www.rfc-editor.org/info/rfc5234>.

   [RFC5888]  Camarillo, G. and H. Schulzrinne, "The Session Description
              Protocol (SDP) Grouping Framework", RFC 5888,
              DOI 10.17487/RFC5888, June 2010,
              <https://www.rfc-editor.org/info/rfc5888>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/info/rfc8446>.

   [RFC8550]  Schaad, J., Ramsdell, B., and S. Turner, "Secure/
              Multipurpose Internet Mail Extensions (S/MIME) Version 4.0
              Certificate Handling", RFC 8550, DOI 10.17487/RFC8550,
              April 2019, <https://www.rfc-editor.org/info/rfc8550>.






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10.2.  Informative References

   [ISO23090]
              "Information technology -- Coded representation of
              immersive media -- Part 2: Omnidirectional MediA Format
              (OMAF) 2nd Edition", ISO ISO 23090-2:2020(E), February
              2020.

   [RFC7205]  Romanow, A., Botzko, S., Duckworth, M., and R. Even, Ed.,
              "Use Cases for Telepresence Multistreams", RFC 7205,
              DOI 10.17487/RFC7205, April 2014,
              <https://www.rfc-editor.org/info/rfc7205>.

   [TS26.223]
              "3rd Generation Partnership Project; Technical
              Specification Group Services and System Aspects;
              Telepresence using the IP Multimedia Subsystem (IMS);
              Media Handling and Interaction", 3GPP TS26.223, March
              2020.

Author's Address

   Rohit Abhishek
   Tencent
   2747 Park Blvd
   Palo Alto  94588
   USA

   Email: rabhishek@rabhishek.com






















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