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Versions: 00 01 02 03 RFC 3803

     Network Working Group                                    Greg Vaudreuil
     Internet Draft                                      Lucent Technologies
     Expires in six months                                     Glenn Parsons
     Obsoletes:  RFC 2424                                    Nortel Networks
                                                            October 22, 2001
     
     
                                  Content Duration
                               MIME Header Definition
     
                        <draft-ietf-vpim-vpimv2r2-dur-02.txt>
     
     
     Status of this Memo
     
        This document is an Internet-Draft and is in full conformance with all
        provisions of Section 10 of RFC2026.
     
        Internet-Drafts are working documents of the Internet Engineering Task
        Force (IETF), its areas, and its working groups. Note that other groups
        may also distribute working documents as Internet-Drafts. Internet-
        Drafts are draft documents valid for a maximum of six months and may be
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        inappropriate to use Internet- Drafts as reference material or to cite
        them other than as "work in progress."
     
        The list of current Internet-Drafts can be accessed at
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        The list of Internet-Draft Shadow Directories can be accessed at
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      Abstract
     
        This document describes the MIME header Content-Duration that is
        intended for use with any time varying media content (typically
        audio/* or video/*).
     
        This document obsoletes RFC 2424.
     
     
     Copyright Notice
     
        Copyright (C) The Internet Society (2001).  All Rights Reserved.
     
     
     
     
     
     
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     Internet Draft             Content Duration           October 22, 2001
     
     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.
     
     
     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.
     
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     Internet Draft             Content Duration           October 22, 2001
     
     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.
     
     
     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
     
        [DUR] G. Parsons and G. Vaudreuil, "Content Duration MIME Header
        Definition", RFC 2424, September 1998.
     
        [MIME2] Freed, N., and N. Borenstein, "Multipurpose Internet Mail
        Extensions (MIME) Part Two: Media Types", RFC 2046, November 1996.
     
        [VPIM2] Vaudreuil, G., and G. Parsons, "Voice Profile for Internet
        Mail - version 2", RFC 2421, September 1998.
     
        [VPIM2R2] Vaudreuil, G., and G. Parsons, "Voice Profile for Internet
        Mail - version 2", <draft ietf                                 -    -vpim-vpimv2r2-04.txt>, October 22, 2001.
     
        [REQ] S. Bradner, "Key words for use in RFCs to Indicate Requirement
        Levels", RFC 2119, March 1997.
     
     
     
     
     
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     Internet Draft             Content Duration           October 22, 2001
     
     6. Authors' Addresses
     
        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
     
        Gregory M. Vaudreuil
        Lucent Technologies
        7291 Williamson Rd
        Dallas, TX  75214
        United States
     
        Phone/Fax: +1-972-733-2722
        Email: gregv@ieee.org
     
     
     7. Full Copyright Statement
     
        Copyright (C) The Internet Society (2001).  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 assigns.
     
        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 HEREIN WILL NOT
        INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR
        FITNESS FOR A PARTICULAR PURPOSE.
     
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