MMUSIC O. Levin, Ed.
Internet-Draft Microsoft Corporation
Expires: August 15, 2004 R. Even
Polycom
P. Hagendorf
RADVISION
February 15, 2004
XML Schema for Media Control
draft-levin-mmusic-xml-schema-media-control-03
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
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This Internet-Draft will expire on August 15, 2004.
Copyright Notice
Copyright (C) The Internet Society (2004). All Rights Reserved.
Abstract
This document defines an XML Schema for Media Control in a tightly
controlled environment. The current version includes commands for
managing of video streams only. Implementation of this schema for
interactive video applications in SIP environments significantly
improves user experience.
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Table of Contents
1. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Background . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. The Video Control Commands . . . . . . . . . . . . . . . . . . 6
5. The Schema Definition . . . . . . . . . . . . . . . . . . . . 7
6. Error Handling . . . . . . . . . . . . . . . . . . . . . . . . 9
7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
8. The Schema Applications . . . . . . . . . . . . . . . . . . . 12
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
10. URN for XML schema . . . . . . . . . . . . . . . . . . . . . . 15
11. Security Considerations . . . . . . . . . . . . . . . . . . . 16
12. Changes since -02 . . . . . . . . . . . . . . . . . . . . . . 17
Normative References . . . . . . . . . . . . . . . . . . . . . 18
Informative References . . . . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 19
Intellectual Property and Copyright Statements . . . . . . . . 20
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1. Conventions
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 [1].
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2. Introduction
This document defines an XML Schema for Media Control in a tightly
controlled environment. The current version includes commands for
managing of video streams only. Implementation of this schema for
interactive video applications in SIP [3] environments significantly
improves user experience. Both end users and conferencing servers
SHOULD implement this mechanism.
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3. Background
SIP typically uses RTP [6] for transferring of real time media.
RTP is augmented by a control protocol (RTCP) to allow monitoring of
the data delivery in a manner scalable to large multicast networks.
The RTCP feedback mechanism [10] has been introduced in order to
improve basic RTCP feedback time in case of loss conditions across
different coding schemes. (Previously, a subset of this functionality
was defined for H.261 [2] only).
The mentioned above techniques address signaling of loss conditions
and the recommended recovery steps. Currently, there is no standard
way to express required operations on media streams as a result of
application logic rather than a result of loss conditions.
Of course, each command MUST be validated by the remote entity
against current media capacity and network conditions before being
executed.
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4. The Video Control Commands
Output of a video CODEC is a frame. The frame can carry complete (in
time) information about a picture or about a picture segment. These
frames are known as "Intra" frames. In order to save bandwidth, other
frames can carry only changes relative to previously sent frames.
Frames carrying relative information are known as "Inter" frames.
Some CODECs (such as H.261 and H.263), in addition to a "full"
picture, have a notion of picture slices: MB (Macro Block) and GOB
(Group Of Blocks).
Based on application logic (such as need to present a new video
source), the application needs to have an ability to explicitly
request from a remote encoder the complete (in-time) information
about a "full" picture or a specific slice of the picture.
Additionally, in case the encoder is aware of upcoming changes in the
transmitted stream (that would result in synchronization lost by the
decoder), the encoder needs to be able to request the decoder to
freeze the picture, i.e. to stop presenting the changes until a new
stable image is encoded and transmitted.
In order to meet the presented requirements, four video primitives
are defined by this document.
The following commands are sent to the remote encoder:
o Video Picture Fast Update
o Video GOB Fast Update (first_GOB, no_of_GOBs)
o Video MB Fast Update (first_GOB, first_MB, no_of_MBs)
The following command is sent to the remote decoder:
o Video Picture Freeze
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5. The Schema Definition
See RFCXXXX.
END Levin, et al. Expires August 15, 2004 [Page 15] Internet-Draft Media Control February 2004 11. Security Considerations This document doesn’t introduce new security requirements beyond covered in [4]. Levin, et al. Expires August 15, 2004 [Page 16] Internet-Draft Media Control February 2004 12. Changes since -02 o This version contains editorial changes only. o The XML schema is identical to version -02. Levin, et al. Expires August 15, 2004 [Page 17] Internet-Draft Media Control February 2004 Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [2] Turletti, T., "RTP Payload Format for H.261 Video Streams", RFC 2032, October 1996. [3] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M. and E. Schooler, "SIP: Session Initiation Protocol", RFC 3261, June 2002. [4] Donovan, S., "The SIP INFO Method", RFC 2976, October 2000. [5] Camarillo, G., Eriksson, G., Holler, J. and H. Schulzrinne, "Grouping of Media Lines in the Session Description Protocol (SDP)", RFC 3388, December 2002. [6] Schulzrinne, H., Casner, S., Frederick, R. and V. Jacobson, "RTP: A Transport Protocol for Real-Time Applications", RFC 3550, July 2003. [7] Murata, M., St. Laurent, S. and D. Kohn, "XML Media Types", RFC 3023, January 2001. [8] Levinson, E., "SGML Media Types", RFC 1874, December 1995. [9] Mealling, M., "The IETF XML Registry", draft-mealling-iana-xmlns-registry-05 (work in progress), June 2003. Levin, et al. Expires August 15, 2004 [Page 18] Internet-Draft Media Control February 2004 Informative References [10] Ott, J. and S. Wenger, "Extended RTP Profile for RTCP-based Feedback(RTP/AVPF)", draft-ietf-avt-rtcp-feedback-08 (work in progress), February 2004. Authors' Addresses Orit Levin (editor) Microsoft Corporation One Microsoft Way Redmond, WA 98052 USA EMail: oritl@microsoft.com Roni Even Polycom 94 Derech Em Hamoshavot Petach Tikva, 49130 Israel EMail: roni.even@polycom.co.il Pierre Hagendorf RADVISION 24, Raul Wallenberg St. Tel-Aviv, 69719 Israel EMail: pierre@radvision.com Levin, et al. Expires August 15, 2004 [Page 19] Internet-Draft Media Control February 2004 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any intellectual property or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; neither does it represent that it has made any effort to identify any such rights. Information on the IETF's procedures with respect to rights in standards-track and standards-related documentation can be found in BCP-11. Copies of claims of rights made available for publication and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementors or users of this specification can be obtained from the IETF Secretariat. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights which may cover technology that may be required to practice this standard. Please address the information to the IETF Executive Director. Full Copyright Statement Copyright (C) The Internet Society (2004). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assignees. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION Levin, et al. Expires August 15, 2004 [Page 20] Internet-Draft Media Control February 2004 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Levin, et al. Expires August 15, 2004 [Page 21]