Network Working Group G. Vaudreuil
Request for Comments: 2424 Lucent Technologies
Category: Standards Track G. Parsons
Northern Telecom
September 1998
Network Working Group G. Vaudreuil
Request for Comments: 2424 Lucent Technologies
Category: Standards Track G. Parsons
Northern Telecom
September 1998
Content Duration MIME Header Definition
内容持续时间MIME头定义
Status of this Memo
本备忘录的状况
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.
本文件规定了互联网社区的互联网标准跟踪协议，并要求进行讨论和提出改进建议。有关本协议的标准化状态和状态，请参考当前版本的“互联网官方协议标准”（STD 1）。本备忘录的分发不受限制。
Copyright Notice
版权公告
Copyright (C) The Internet Society (1998). All Rights Reserved.
版权所有（C）互联网协会（1998年）。版权所有。
Overview
概述
This document describes the MIME header Content-Duration that is
intended for use with any timed media content (typically audio/* or
video/*).
This document describes the MIME header Content-Duration that is
intended for use with any timed media content (typically audio/* or
video/*).
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 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.
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.
时变媒体内容（例如，语音消息或视频剪辑）具有固有的持续时间。许多音频和视频编码可能包括其持续时间作为报头信息，或者可能允许基于数据的字节长度进行精确计算。但是，在MIME头中显示内容的持续时间可能会很有用，以便在不处理实际内容的情况下进行简单的确定。
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 [REQ].
本文件中的关键词“必须”、“不得”、“要求”、“应”、“不应”、“应”、“不应”、“建议”、“可”和“可选”应按照[REQ]中的说明进行解释。
The Content-Duration field's value is a single number specifying the time duration in seconds of the content. Formally:
“内容持续时间”字段的值是一个数字，指定内容的持续时间（以秒为单位）。正式地：
duration := "Content-Duration" ":" 1*10DIGIT
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.
请注意，实际上（尽管在MIME媒体中不太可能），持续时间数值的上限为（2^^31-1）或2147483647。
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.
此字段表示关联的时变媒体内容的持续时间。持续时间以秒为单位，无单位标记。时间值应该是精确的，但是如果不打开内容并播放，则无法知道持续时间的精确值。如果必须知道准确值，则应使用后一种方法。此机制只允许在标头中放置发送方确定的持续时间值，以便于访问。
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.
虽然有几种方式向收件人显示此持续时间（例如，打开音频附件时使用收件箱标题），但在接收时实际使用此字段是本地实现问题。
In this example the content duration represents 33 seconds:
在此示例中，内容持续时间表示33秒：
Content-Duration: 33
内容持续时间：33
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.
音频/32KADPCM子类型的内容持续时间标头字段是VPIM规范[VPIM2]的一个有用组件。所有VPIM消息必须包含此子类型，才能承载语音消息的音频。在某些情况下（例如，在简单的MIME或非MIME桌面上查看），无需打开音频内容即可获得语音消息的持续时间可能很有用。
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.
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.
Glenn W. Parsons Northern Telecom P.O. Box 3511, Station C Ottawa, ON K1Y 4H7 Canada
加拿大K1Y 4H7渥太华C站Glenn W.Parsons Northern Telecom邮政信箱3511
Phone: +1-613-763-7582
Fax: +1-613-763-4461
EMail: Glenn.Parsons@Nortel.ca
Phone: +1-613-763-7582
Fax: +1-613-763-4461
EMail: Glenn.Parsons@Nortel.ca
Gregory M. Vaudreuil Lucent Technologies 17080 Dallas Parkway Dallas, TX 75248-1905 United States
Gregory M.Vaudreuil-Lucent Technologies 17080美国德克萨斯州达拉斯市达拉斯公园路75248-1905
Phone/Fax: +1-972-733-2722
EMail: GregV@Lucent.Com
Phone/Fax: +1-972-733-2722
EMail: GregV@Lucent.Com
[MIME2] Freed, N., and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types", RFC 2046, November 1996.
[MIME2]Freed，N.和N.Borenstein，“多用途互联网邮件扩展（MIME）第二部分：媒体类型”，RFC 20461996年11月。
[VPIM2] Vaudreuil, G., and G. Parsons, "Voice Profile for Internet Mail - version 2", RFC 2421, September 1998.
[VPIM2]Vaudreuil，G.和G.Parsons，“互联网邮件语音配置文件-第2版”，RFC 24211998年9月。
[REQ] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[REQ]Bradner，S.，“在RFC中用于指示需求水平的关键词”，BCP 14，RFC 2119，1997年3月。
Copyright (C) The Internet Society (1998). All Rights Reserved.
版权所有（C）互联网协会（1998年）。版权所有。
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.
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The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns.
上述授予的有限许可是永久性的，互联网协会或其继承人或受让人不会撤销。
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