Negotiation of Generic Image Attributes in the Session Description Protocol (SDP)
RFC 6236
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RFC - Proposed Standard
(May 2011; Errata)
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Last updated |
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2015-10-14
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draft-johansson-mmusic-image-attributes
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IETF
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RFC 6236 (Proposed Standard)
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Responsible AD |
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Robert Sparks
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Tom Taylor (tom111.taylor@bell.net) is the Document Shepherd.
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Internet Engineering Task Force (IETF) I. Johansson
Request for Comments: 6236 Ericsson AB
Category: Standards Track K. Jung
ISSN: 2070-1721 Samsung Electronics Co., Ltd.
May 2011
Negotiation of Generic Image Attributes in
the Session Description Protocol (SDP)
Abstract
This document proposes a new generic session setup attribute to make
it possible to negotiate different image attributes such as image
size. A possible use case is to make it possible for a low-end hand-
held terminal to display video without the need to rescale the image,
something that may consume large amounts of memory and processing
power. The document also helps to maintain an optimal bitrate for
video as only the image size that is desired by the receiver is
transmitted.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6236.
Johansson & Jung Standards Track [Page 1]
RFC 6236 Image Attributes in SDP May 2011
Copyright Notice
Copyright (c) 2011 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
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. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements . . . . . . . . . . . . . . . . . . . . . . . 4
2. Conventions Used in This Document . . . . . . . . . . . . . . 5
3. Specification of the 'imageattr' SDP Attribute . . . . . . . . 5
3.1. Attribute Syntax . . . . . . . . . . . . . . . . . . . . . 5
3.1.1. Overall View of Syntax . . . . . . . . . . . . . . . . 5
3.2. Considerations . . . . . . . . . . . . . . . . . . . . . . 11
3.2.1. No imageattr in First Offer . . . . . . . . . . . . . 11
3.2.2. Different Payload Type Numbers in Offer and Answer . . 11
3.2.3. Asymmetry . . . . . . . . . . . . . . . . . . . . . . 12
3.2.4. sendonly and recvonly . . . . . . . . . . . . . . . . 12
3.2.5. Sample Aspect Ratio . . . . . . . . . . . . . . . . . 13
3.2.6. SDPCapNeg Support . . . . . . . . . . . . . . . . . . 13
3.2.7. Interaction with Codec Parameters . . . . . . . . . . 14
3.2.8. Change of Display in Middle of Session . . . . . . . . 16
3.2.9. Use with Layered Codecs . . . . . . . . . . . . . . . 16
3.2.10. Addition of Parameters . . . . . . . . . . . . . . . . 16
4. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.1. A High-Level Example . . . . . . . . . . . . . . . . . . . 16
4.2. Detailed Examples . . . . . . . . . . . . . . . . . . . . 17
4.2.1. Example 1 . . . . . . . . . . . . . . . . . . . . . . 17
4.2.2. Example 2 . . . . . . . . . . . . . . . . . . . . . . 18
4.2.3. Example 3 . . . . . . . . . . . . . . . . . . . . . . 19
4.2.4. Example 4 . . . . . . . . . . . . . . . . . . . . . . 20
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20
6. Security Considerations . . . . . . . . . . . . . . . . . . . 21
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 21
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 22
8.1. Normative References . . . . . . . . . . . . . . . . . . . 22
8.2. Informative References . . . . . . . . . . . . . . . . . . 22
Johansson & Jung Standards Track [Page 2]
RFC 6236 Image Attributes in SDP May 2011
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