Network Working Group Greg Vaudreuil Internet Draft Octel Communications Expires in six months Glenn Parsons Obsoletes: RFC 1911 Nortel Technology January 22, 1997 Content Duration MIME Header Definition Status of this Memo This document is an Internet Draft. 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 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 a "work in progress". To learn the current status of any Internet-Draft, please check the "1id-abstracts.txt" listing contained in the Internet-Drafts Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or ftp.isi.edu (US West Coast). Overview This document describes the MIME header Content-Duration that is intended for use with any timed media content (typically audio/* or video/*). Internet Draft Content-Duration January 22, 1997 1. Abstract This document describes the MIME header Content-Duration that is intended for use with any timed media content (typically audio/* or video/*). The length of time is represented in seconds. 2. Content-Duration Header Field Many media contents have an inherent time duration, for example a spoken message or a video clip. Many audio and video encodings may include their length 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 superior time unit is (2^^31 - 1) or 2147483647. 2.2 Semantics This field represents the time duration of the associated 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 Vaudreuil, Parsons Expires 7/22/97 [Page 2] Internet Draft Content-Duration January 22, 1997 3. VPIM Usage The Content-Duration header field for 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 defintion introduces the option of explicitly identifying the time duration of an audio/* or fax/* 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. 5. Authors' Addresses Glenn W. Parsons Nortel Technology P.O. Box 3511, Station C Ottawa, ON K1Y 4H7 Canada Phone: +1-613-763-7582 Fax: +1-613-763-8385 Glenn.Parsons@Nortel.ca Gregory M. Vaudreuil Octel Communications 17080 Dallas Parkway Dallas, TX 75248-1905 United States Phone/Fax: +1-972-733-2722 Greg.Vaudreuil@Octel.Com 6. References [MIME2] N. Freed and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types ", RFC 2046, Innosoft, First Virtual, Nov 1996. [VPIM2] Greg Vaudreuil and Glenn Parsons, "Voice Profile for Internet Mail - version 2", Work in Progress, Jan 1997. Vaudreuil, Parsons Expires 7/22/97 [Page 3]