Internet DRAFT - draft-ietf-vpim-vpimv2r2-dur
draft-ietf-vpim-vpimv2r2-dur
Network Working Group Greg Vaudreuil
Internet Draft Lucent Technologies
Expires in six months Glenn Parsons
Obsoletes: RFC 2424 Nortel Networks
February 14, 2002
Content Duration
MIME Header Definition
<draft-ietf-vpim-vpimv2r2-dur-03.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
updated, replaced, or obsoleted by other documents at any time. It is
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
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
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 (2002). All Rights Reserved.
Vaudreuil & Parsons Expires: August 14, 2002 1
Internet Draft Content Duration February 14, 2002
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.
Vaudreuil & Parsons Expires April 22, 2002 [Page 2]
Internet Draft Content Duration February 14, 2002
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.
Vaudreuil & Parsons Expires April 22, 2002 [Page 3]
Internet Draft Content Duration February 14, 2002
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. Changes from RFC 2424
Only editoral and boilerplate changes from RFC 2424 have been made to
this document.
Vaudreuil & Parsons Expires April 22, 2002 [Page 4]
Internet Draft Content Duration February 14, 2002
8. Full Copyright Statement
Copyright (C) The Internet Society (2002). 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.
Vaudreuil & Parsons Expires April 22, 2002 [Page 5]
