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rfc:rfc3803

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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