Negotiation of Generic Image Attributes in the Session Description Protocol (SDP)
RFC 6236
Document | Type | RFC - Proposed Standard (May 2011; Errata) | |
---|---|---|---|
Authors | Kyunghun Jung , Ingemar Johansson | ||
Last updated | 2015-10-14 | ||
Replaces | draft-johansson-mmusic-image-attributes | ||
Stream | Internent Engineering Task Force (IETF) | ||
Formats | plain text html pdf htmlized (tools) htmlized bibtex | ||
Reviews | |||
Stream | WG state | WG Document | |
Document shepherd | No shepherd assigned | ||
IESG | IESG state | RFC 6236 (Proposed Standard) | |
Action Holders |
(None)
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||
Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | Robert Sparks | ||
IESG note | Tom Taylor (tom111.taylor@bell.net) is the Document Shepherd. | ||
Send notices to | (None) |
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 1. Introduction This document proposes a new SDP attribute to make it possible to negotiate different image attributes, such as image size. The term image size is defined here, as it may differ from the physical screenShow full document text