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webm-format.html
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<!DOCTYPE html>
<html lang="en" dir="ltr" typeof="bibo:Document " about="" property="dcterms:language" content="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>WebM EME Stream Format and Initialization Data</title>
<!-- script to register bugs -->
<script src="https://w3c.github.io/webcomponents/assets/scripts/bug-assist.js"></script>
<meta name="bug.product" content="HTML WG">
<meta name="bug.component" content="Encrypted Media Extensions">
<link rel="stylesheet" href="eme.css">
<style>/*****************************************************************
* ReSpec 3 CSS
* Robin Berjon - http://berjon.com/
*****************************************************************/
/* --- INLINES --- */
em.rfc2119 {
text-transform: lowercase;
font-variant: small-caps;
font-style: normal;
color: #900;
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h1 acronym, h2 acronym, h3 acronym, h4 acronym, h5 acronym, h6 acronym, a acronym,
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border: none;
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dfn {
font-weight: bold;
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a.internalDFN {
color: inherit;
border-bottom: 1px solid #99c;
text-decoration: none;
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a.externalDFN {
color: inherit;
border-bottom: 1px dotted #ccc;
text-decoration: none;
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text-decoration: none;
}
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font-style: normal;
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color: #C83500;
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color: #000;
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border-bottom: 3px solid #005a9c;
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background: #005a9c;
color: #fff;
padding: 3px 5px;
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background: #f0f6ff;
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margin-top: 0;
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.section dd > p:last-child {
margin-bottom: 0;
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.section dd {
margin-bottom: 1em;
}
.section dl.attrs dd, .section dl.eldef dd {
margin-bottom: 0;
}
@media print {
.removeOnSave {
display: none;
}
}
</style><link rel="stylesheet" href="https://www.w3.org/StyleSheets/TR/W3C-ED"><!--[if lt IE 9]><script src='https://www.w3.org/2008/site/js/html5shiv.js'></script><![endif]--></head>
<body class="h-entry" role="document" id="respecDocument"><div class="head" role="contentinfo" id="respecHeader">
<p>
<a href="http://www.w3.org/"><img width="72" height="48" src="https://www.w3.org/Icons/w3c_home" alt="W3C"></a>
</p>
<h1 class="title p-name" id="title" property="dcterms:title">WebM EME Stream Format and Initialization Data</h1>
<h2 property="dcterms:issued" datatype="xsd:dateTime" content="2014-11-26T19:22:20.000Z" id="w3c-editor-s-draft-26-november-2014"><abbr title="World Wide Web Consortium">W3C</abbr> Editor's Draft <time class="dt-published" datetime="2014-11-26">26 November 2014</time></h2>
<dl>
<dt>This version:</dt>
<dd><a class="u-url" href="https://w3c.github.io/encrypted-media/cenc-format.html">https://w3c.github.io/encrypted-media/cenc-format.html</a></dd>
<dt>Latest published version:</dt>
<dd><a href="http://www.w3.org/TR/encrypted-media/">http://www.w3.org/TR/encrypted-media/</a></dd>
<dt>Latest editor's draft:</dt>
<dd><a href="https://w3c.github.io/encrypted-media/cenc-format.html">https://w3c.github.io/encrypted-media/cenc-format.html</a></dd>
<dt>Editors:</dt>
<dd class="p-author h-card vcard" rel="bibo:editor" inlist=""><span typeof="foaf:Person"><span property="foaf:name" class="p-name fn">David Dorwin</span>, <a rel="foaf:workplaceHomepage" class="p-org org h-org h-card" href="https://www.google.com/">Google Inc.</a></span>
</dd>
<dd class="p-author h-card vcard" rel="bibo:editor" inlist=""><span typeof="foaf:Person"><span property="foaf:name" class="p-name fn">Adrian Bateman</span>, <a rel="foaf:workplaceHomepage" class="p-org org h-org h-card" href="https://www.microsoft.com/">Microsoft Corporation</a></span>
</dd>
<dd class="p-author h-card vcard" rel="bibo:editor" inlist=""><span typeof="foaf:Person"><span property="foaf:name" class="p-name fn">Mark Watson</span>, <a rel="foaf:workplaceHomepage" class="p-org org h-org h-card" href="https://www.netflix.com/">Netflix Inc.</a></span>
</dd>
<dt>Repository:</dt>
<dd>
<a href="https://github.com/w3c/encrypted-media/">https://github.com/w3c/encrypted-media/</a>
</dd>
</dl>
<p class="copyright">
<a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a> ©
2014
<a href="http://www.w3.org/"><abbr title="World Wide Web Consortium">W3C</abbr></a><sup>®</sup>
(<a href="http://www.csail.mit.edu/"><abbr title="Massachusetts Institute of Technology">MIT</abbr></a>,
<a href="http://www.ercim.eu/"><abbr title="European Research Consortium for Informatics and Mathematics">ERCIM</abbr></a>,
<a href="http://www.keio.ac.jp/">Keio</a>, <a href="http://ev.buaa.edu.cn/">Beihang</a>),
All Rights Reserved.
<abbr title="World Wide Web Consortium">W3C</abbr> <a href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>,
<a href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a> and
<a href="http://www.w3.org/Consortium/Legal/copyright-documents">document use</a>
rules apply.
</p>
<hr>
</div>
<section id="abstract" class="introductory" property="dcterms:abstract" datatype="" typeof="bibo:Chapter" resource="#abstract" rel="bibo:Chapter"><h2 role="heading" id="h2_abstract">Abstract</h2>
<p>This specification defines the stream format and initialization data for using <a href="http://www.webmproject.org/code/specs/container/">WebM</a> with the <a href="index.html#">Encrypted Media Extensions</a>.</p>
</section><section id="sotd" class="introductory" typeof="bibo:Chapter" resource="#sotd" rel="bibo:Chapter"><h2 role="heading" id="h2_sotd">Status of This Document</h2>
<p>
<em>This section describes the status of this document at the time of its publication.
Other documents may supersede this document. A list of current <abbr title="World Wide Web Consortium">W3C</abbr> publications and the
latest revision of this technical report can be found in the <a href="http://www.w3.org/TR/"><abbr title="World Wide Web Consortium">W3C</abbr> technical reports index</a> at
http://www.w3.org/TR/.</em>
</p>
<p>The Working Group maintains <a href="https://www.w3.org/brief/MjY5"> a list of all bug reports that the editors have not yet tried to address</a>.</p>
<p>Implementors should be aware that this specification is not stable. <strong>Implementors who are not taking part in the discussions are likely to find the specification changing out from under them in incompatible ways.</strong> Vendors interested in implementing this specification before it eventually reaches the Candidate Recommendation stage should join the mailing list mentioned below and take part in the discussions.</p>
<p>
This document was published by the <a href="http://www.w3.org/html/wg/">HTML Working Group</a> as an Editor's Draft.
If you wish to make comments regarding this document, please send them to
<a href="mailto:[email protected]">[email protected]</a>
(<a href="mailto:[email protected]?subject=subscribe">subscribe</a>,
<a href="http://lists.w3.org/Archives/Public/public-html-media/">archives</a>).
All comments are welcome.
</p>
<p>
Publication as an Editor's Draft does not imply endorsement by the <abbr title="World Wide Web Consortium">W3C</abbr>
Membership. This is a draft document and may be updated, replaced or obsoleted by other
documents at any time. It is inappropriate to cite this document as other than work in
progress.
</p>
<p>
This document was produced by a group operating under the
<a id="sotd_patent" about="" rel="w3p:patentRules" href="http://www.w3.org/Consortium/Patent-Policy-20040205/">5 February 2004 <abbr title="World Wide Web Consortium">W3C</abbr> Patent
Policy</a>.
<abbr title="World Wide Web Consortium">W3C</abbr> maintains a <a href="https://www.w3.org/2004/01/pp-impl/40318/status" rel="disclosure">public list of any patent
disclosures</a>
made in connection with the deliverables of the group; that page also includes
instructions for disclosing a patent. An individual who has actual knowledge of a patent
which the individual believes contains
<a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#def-essential">Essential
Claim(s)</a> must disclose the information in accordance with
<a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#sec-Disclosure">section
6 of the <abbr title="World Wide Web Consortium">W3C</abbr> Patent Policy</a>.
</p>
<p>This document is governed by the <a id="w3c_process_revision" href="http://www.w3.org/2014/Process-20140801/">1 August 2014 <abbr title="World Wide Web Consortium">W3C</abbr> Process Document</a>.
</p>
</section><section id="toc"><h2 class="introductory" role="heading" id="h2_toc">Table of Contents</h2><ul class="toc" role="directory" id="respecContents"><li class="tocline"><a href="#stream-format" class="tocxref"><span class="secno">1. </span>Stream Format </a></li><li class="tocline"><a href="#detect-encrypt" class="tocxref"><span class="secno">2. </span>Detecting Encryption</a></li><li class="tocline"><a href="#init-data" class="tocxref"><span class="secno">3. </span>Initialization Data and Events</a></li></ul></section>
<section id="stream-format" typeof="bibo:Chapter" resource="#stream-format" rel="bibo:Chapter">
<!--OddPage--><h2 role="heading" id="h2_stream-format"><span class="secno">1. </span>Stream Format </h2>
<p><a href="http://wiki.webmproject.org/encryption/webm-encryption-rfc">Encrypted WebM streams</a> are encrypted at the block level with AES-128 CTR encryption.
The container shall include appropriate values within the <a href="http://matroska.org/technical/specs/index.html#ContentEncryption">ContentEncryption</a> element.
</p>
<p>WebM streams may be partially encrypted, both at the <a href="http://matroska.org/technical/specs/index.html#LevelTrack">Track</a> level and the block level.
In the former case, a subset of Tracks in the stream have a <a href="http://matroska.org/technical/specs/index.html#ContentEncryption">ContentEncryption</a> element.
In the latter case, a subset of the blocks within a Track containing a <a href="http://matroska.org/technical/specs/index.html#ContentEncryption">ContentEncryption</a> element are marked as encrypted.
</p>
</section>
<section id="detect-encrypt" typeof="bibo:Chapter" resource="#detect-encrypt" rel="bibo:Chapter">
<!--OddPage--><h2 role="heading" id="h2_detect-encrypt"><span class="secno">2. </span>Detecting Encryption</h2>
<p>When a WebM <a href="http://matroska.org/technical/specs/index.html#LevelTrack">Track</a> is parsed, the presence of a <a href="http://matroska.org/technical/specs/index.html#ContentEncKeyID">ContentEncKeyID</a> element indicates that blocks in the track may be encrypted.
</p><p>For the purposes of the <a href="index.html#encrypted-block-encountered">encrypted block encountered</a>, encrypted blocks are those marked encrypted by the <a href="http://wiki.webmproject.org/encryption/webm-encryption-rfc#TOC-4.6-Signal-Byte-Format">Signal Byte.</a></p>
</section>
<section id="init-data" typeof="bibo:Chapter" resource="#init-data" rel="bibo:Chapter">
<!--OddPage--><h2 role="heading" id="h2_init-data"><span class="secno">3. </span>Initialization Data and Events</h2>
<p><a href="index.html#initialization-data">Initialization Data</a> is always a single <a href="index.html#decryption-key-id">key ID</a>, as defined by the <a href="http://matroska.org/technical/specs/index.html#ContentEncKeyID">ContentEncKeyID</a> element of the <a href="http://matroska.org/technical/specs/index.html#LevelTrack">Track</a>.</p>
<p>Each time a <a href="http://matroska.org/technical/specs/index.html#ContentEncKeyID">ContentEncKeyID</a> element is encountered, the <a href="index.html#initdata-encountered">Initialization Data encountered</a> algorithm shall be invoked with <var title="">initDataType</var> = "webm" and <var title="">initData</var> = the value in that element.</p>
</section>
<form id="bug-assist-form" action="//www.w3.org/Bugs/Public/enter_bug.cgi" target="_blank">See a problem? Select text and <input type="submit" accesskey="f" value="file a bug" style="font-family: Tahoma, sans-serif; font-size: 10px;"><input type="hidden" name="comment" value=""><input type="hidden" name="product" value="HTML WG"><input type="hidden" name="component" value="Encrypted Media Extensions">.</form></body></html>