Network Working Group G. Vaudreuil
Request for Comments: 3803 Lucent Technologies
Obsoletes: 2424 G. Parsons
Category: Standards Track Nortel Networks
June 2004
Content Duration MIME Header Definition
Status of this Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2004).
Abstract
This document describes the MIME header Content-Duration that is
intended for use with any time varying media content (typically
audio/* or video/*).
1. Introduction
This document describes the MIME header Content-Duration that is
intended for use with any time varying media content (typically
audio/* or video/*). The length of time is represented in seconds
without any units indication. This document obsoletes RFC 2424.
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 [REQ].
2. Content-Duration Header Field
Time varying media contents, for example, a spoken voice message or a
video clip, have an inherent time duration. Many audio and video
encodings may include their duration as header information or may
allow accurate calculation based on the byte length of the data.
However, it may be useful to present the time duration of the content
in a MIME header to allow its simple determination without dealing
with the actual content.
Vaudreuil, et al. Standards Track [Page 1]
RFC 3803 Content Duration MIME Header Definition June 2004 2.1. Syntax The Content-Duration field's value is a single number specifying the time duration in seconds of the content. Formally: duration := "Content-Duration" ":" 1*10DIGIT Note that practically (though highly unlikely in MIME media), the upper bound on the numerical value of the time duration is (2^^31 -1) or 2147483647. 2.2. Semantics This field represents the time duration of the associated time varying media content. The time duration is noted in seconds with no units tag. The time value should be exact, however the exact value of the time duration cannot be known without opening the content and playing it. If an exact value must be known, then the latter method should be used. This mechanism simply allows placing a sender determined time duration value in the header for easy access. Though there are several ways to present this duration to the recipient (e.g., with the inbox headers, when audio attachment opened), the actual use of this field on reception is a local implementation issue. 2.3. Example In this example the content duration represents 33 seconds: Content-Duration: 33 3. VPIM Usage The Content-Duration header field for the audio/32KADPCM sub-type is a useful component of the VPIM specification [VPIM2]. All VPIM Messages MUST contain this sub-type to carry the audio of a voice message. It may be useful in some instances (e.g., viewing on a simple MIME or non-MIME desktop) to have the time duration of the voice message available without having to open the audio content. Vaudreuil, et al. Standards Track [Page 2]
RFC 3803 Content Duration MIME Header Definition June 2004 4. Security Considerations This definition introduces the option of explicitly identifying the time duration of an audio/* or video/* content outside of the binary data that forms the content. In some environments (though likely not the majority), the identification of the actual time duration in a header field may be a security issue and as a result should not be noted. Reliance on the time indicated in this header field cannot be trusted for the purposes of determining the exact size of the data. The exact length of the data must be determined by examining the data itself. 5. References 5.1. Normative References [MIME2] Gellens, R., "The Text/Plain Format Parameter", RFC 2646, August 1999. [VPIM2R2] Vaudreuil, G., and G. Parsons, "Voice Profile for Internet Mail - version 2 (VPIMv2)", RFC 3801, June 2004. [REQ] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. 5.2. Informative References [DUR] Parsons, G. and G. Vaudreuil, "Content Duration MIME Header Definition", RFC 2424, September 1998. [VPIM2] Vaudreuil, G. and G. Parsons, "Voice Profile for Internet Mail - version 2", RFC 2421, September 1998. 6. Changes from RFC 2424 Only editorial and boilerplate changes from RFC 2424 have been made to this document. Vaudreuil, et al. Standards Track [Page 3]
RFC 3803 Content Duration MIME Header Definition June 2004 7. Authors' Addresses Gregory M. Vaudreuil Lucent Technologies 7291 Williamson Rd Dallas, TX 75214 United States EMail: gregv@ieee.org Glenn W. Parsons Nortel Networks P.O. Box 3511, Station C Ottawa, ON K1Y 4H7 Canada Phone: +1-613-763-7582 Fax: +1-613-763-2697 EMail: gparsons@nortelnetworks.com Vaudreuil, et al. Standards Track [Page 4]
RFC 3803 Content Duration MIME Header Definition June 2004 8. Full Copyright Statement Copyright (C) The Internet Society (2004). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Intellectual Property The IETF takes no position regarding the validity or scope of any Intellectual Property Rights 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; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat 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 implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf- ipr@ietf.org. Acknowledgement Funding for the RFC Editor function is currently provided by the Internet Society. Vaudreuil, et al. Standards Track [Page 5]
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