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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>ISO Common Encryption 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">
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<style>/*****************************************************************
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<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">ISO Common Encryption EME Stream Format and Initialization Data</h1>
<h2 property="dcterms:issued" datatype="xsd:dateTime" content="2014-11-26T19:21:00.000Z" 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>
<dd class="p-author h-card vcard" rel="bibo:editor" inlist=""><span typeof="foaf:Person"><span property="foaf:name" class="p-name fn">Jerry Smith</span>, <a rel="foaf:workplaceHomepage" class="p-org org h-org h-card" href="https://www.microsoft.com/">Microsoft Corporation</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
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rules apply.
</p>
<hr>
</div>
<!-- TODO: Use styles for ISO boxes like the MSE registry. -->
<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 ISO Base media File Format [<cite><a class="bibref" href="#bib-BMFF">BMFF</a></cite>] content using the ISO Common Encryption ('cenc') protection scheme [<cite><a class="bibref" href="#bib-CENC-1ST">CENC-1ST</a></cite>] with the <a href="index.html#">Encrypted Media Extensions</a>.
It also defines a common SystemID and PSSH box format for use with Encrypted Media Extensions.
</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><li class="tocline"><a href="#common-system" class="tocxref"><span class="secno">4. </span>Common SystemID and PSSH Box Format</a><ul class="toc"><li class="tocline"><a href="#common-system-definition" class="tocxref"><span class="secno">4.1 </span>Definition</a></li><li class="tocline"><a href="#example" class="tocxref"><span class="secno">4.2 </span>Example</a></li></ul></li><li class="tocline"><a href="#references" class="tocxref"><span class="secno">A. </span>References</a><ul class="toc"><li class="tocline"><a href="#normative-references" class="tocxref"><span class="secno">A.1 </span>Normative references</a></li></ul></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>Under the ISO Common Encryption ('cenc') protection scheme [<cite><a class="bibref" href="#bib-CENC-1ST">CENC-1ST</a></cite>], ISO Base media File Format [<cite><a class="bibref" href="#bib-BMFF">BMFF</a></cite>] content is encrypted at the sample level with AES-128 CTR encryption. This protection method enables multiple Key Systems to decrypt the same media content.</p>
<p>Each key is identified by a <a href="index.html#decryption-key-id">key ID</a> and each encrypted sample is associated with the Key ID of the key needed to decrypt it. This association is signaled either through the specification of a default Key ID in the track encryption box ('tenc') or by assigning the sample to a Sample Group, the definition of which specifies a Key ID. Common encryption files may contain a mixture of encrypted and unencrypted samples.</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>Protection scheme signaling conforms with ISO Base media File Format [<cite><a class="bibref" href="#bib-BMFF">BMFF</a></cite>]. When protection has been applied, the stream type will be transformed to 'encv' for video or 'enca' for audio, with a Protection Scheme Information Box ('sinf') added to the sample entry in the Sample Description Box ('stsd'). The Protection Scheme Information Box ('sinf') will contain a Scheme Type Box ('schm') with a scheme_type field set to a value of 'cenc' (Common Encryption).</p>
<p>The "encrypted block" is a sample. Determining whether a sample is encrypted depends on the corresponding Track Encryption Box ('tenc') and the sample group with grouping type 'seig' (CencSampleEncryption group), if any, associated with the sample.
The default encryption state of a sample is defined by the IsEncrypted flag in the associated track encryption box ('tenc'). This default state may be modified by the IsEncrypted flag in the SampleGroupDescriptionBox ('sgpd'), pointed to by an index in the SampleToGroupBox ('sbgp').</p>
<p>Samples can be partially encrypted, specified by subsample information referenced by SampleAuxiliaryInformationSizesBox ('saiz') and SampleAuxiliaryInformationOffsetsBox ('saio') boxes.</p>
<p>For complete information, see [<cite><a class="bibref" href="#bib-CENC-1ST">CENC-1ST</a></cite>].</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>Common Encryption files may contain one or more protection system specific header ('pssh') boxes, each for a unique SystemID at each location where a 'pssh' box is necessary.</p>
<p><a href="index.html#initialization-data">Initialization Data</a> is always one or more concatenated 'pssh' boxes.
An implementation (the user agent and/or CDM) <em class="rfc2119" title="MUST">MUST</em> be able to examine multiple 'pssh' boxes in the Initialization Data to find a 'pssh' box that it supports.
At least one of the concatenated 'pssh' boxes <em class="rfc2119" title="SHOULD">SHOULD</em> contain the SystemID defined in the <a href="#common-system">Common SystemID and PSSH Box Format</a> section.
</p>
<p>Each time one or more 'pssh' boxes are encountered, the <a href="index.html#initdata-encountered">Initialization Data encountered</a> algorithm shall be invoked with <var title="">initDataType</var> = "cenc" and <var title="">initData</var> = the 'pssh' box(es). Multiple 'pssh' boxes <em class="rfc2119" title="MUST">MUST</em> be provided together if and only if they appear directly next to each other in the file.</p>
<p>If a supported 'pssh' box (based on SystemID) is not found while processing the <var>initData</var> in the <code><a href="index.html#widl-MediaKeys-createSession-MediaKeySession-SessionType-sessionType">createSession()</a></code> algorithm, follow the algorithm step for "<var>init data</var> is not supported by the <var>cdm</var>."</p>
<div class="note"><div class="note-title" aria-level="1" role="heading" id="h_note_1"><span>Note</span></div><p class="">ISO Common Encryption 2nd Edition [<cite><a class="bibref" href="#bib-CENC-2ND">CENC-2ND</a></cite>] also specifies storage of a 'pssh' box base64 encoded in an XML element of the form <cenc:pssh (base64 'pssh')>. For instance, DASH manifests may provide 'pssh' boxes in this format, each contained in a ContentProtection Descriptor element identified by a SystemID. These 'pssh' boxes may be decoded and concatenated by an application to provide equivalent Initialization Data to that stored in movie or movie fragment boxes.</p></div>
</section>
<section id="common-system" typeof="bibo:Chapter" resource="#common-system" rel="bibo:Chapter">
<!--OddPage--><h2 role="heading" id="h2_common-system"><span class="secno">4. </span>Common SystemID and PSSH Box Format</h2>
<p>This section defines a common open SystemID and PSSH box format for use with EME.
Key System implementations supporting ISO Common Encryption <em class="rfc2119" title="MUST">MUST</em> support this SystemID and format.
Media resources for use with EME <em class="rfc2119" title="SHOULD">SHOULD</em> contain appropriate PSSH box(es) for this SystemID.
</p><div class="note"><div class="note-title" aria-level="1" role="heading" id="h_note_2"><span>Note</span></div><p class="">
Use of this SystemID is <em class="rfc2119" title="RECOMMENDED">RECOMMENDED</em> for applications, packagers, and implementors.
Use of other SystemIDs with the EME APIs is discouraged.
'pssh' box(es) for this SystemID <em class="rfc2119" title="SHOULD">SHOULD</em> be included in all new or repackaged content so that the content can be used with any compliant Key System.
For existing content, applications may alternatively obtain a 'pssh' box containing this SystemID or another Initialization Data Type (e.g. <a href="keyids-format.html">keyids</a>) from another source.
</p></div>
<div class="note"><div class="note-title" aria-level="1" role="heading" id="h_note_3"><span>Note</span></div><p class="">Implementations <em class="rfc2119" title="MAY">MAY</em> support other SystemIDs for backwards compatibility with existing streams.</p></div>
<p><a href="index.html#clear-key">Clear Key</a> uses this SystemID for ISO Common Encryption content.
When <code><a href="index.html#widl-MediaKeys-createSession-MediaKeySession-SessionType-sessionType">createSession()</a></code> is called with <var>initDataType</var> "cenc", the Clear Key CDM will use the PSSH box with this SystemID to generate a license request.
</p>
<section id="common-system-definition" typeof="bibo:Chapter" resource="#common-system-definition" rel="bibo:Chapter">
<h3 role="heading" id="h3_common-system-definition"><span class="secno">4.1 </span>Definition</h3>
<p>The SystemID is 1077efec-c0b2-4d02-ace3-3c1e52e2fb4b.</p>
<p>The PSSH box format is as follows. It follows version 1 of the 'pssh' box as defined in ISO Common Encryption 2nd Edition [<cite><a class="bibref" href="#bib-CENC-2ND">CENC-2ND</a></cite>].</p>
<dl>
<dt>version</dt>
<dd>1</dd>
<dt>KID and KID_count</dt>
<dd>The <a href="index.html#decryption-key-id">key ID</a>(s) represented by the PSSH box. For example, those key ID(s) used by the Movie ('moov') or Movie Fragment ('moof').</dd>
<dt>Data and DataSize</dt>
<dd>Reserved for future use. DataSize <em class="rfc2119" title="SHALL">SHALL</em> be set to 0 when constructing this box. When processing, if dataSize is non-zero the Data field <em class="rfc2119" title="SHALL">SHALL</em> be ignored.</dd>
</dl>
</section>
<section class="informative" id="example">
<h3 role="heading" id="h3_example"><span class="secno">4.2 </span>Example</h3><p><em>This section is non-normative.</em></p>
<p>The following example contains two key IDs.</p>
<div class="example"><div class="example-title"><span>Example 1</span></div><pre class="example">var pssh = [
0x00, 0x00, 0x00, 0x4c, 0x70, 0x73, 0x73, 0x68, // BMFF box header (76 bytes, 'pssh')
0x01, 0x00, 0x00, 0x00, // Full box header (version = 1, flags = 0)
0x10, 0x77, 0xef, 0xec, 0xc0, 0xb2, 0x4d, 0x02, // SystemID
0xac, 0xe3, 0x3c, 0x1e, 0x52, 0xe2, 0xfb, 0x4b,
0x00, 0x00, 0x00, 0x02, // KID_count (2)
0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, // First KID ("0123456789012345")
0x38, 0x39, 0x30, 0x31, 0x32, 0x33, 0x34, 0x35,
0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, // Second KID ("ABCDEFGHIJKLMNOP")
0x49, 0x4a, 0x4b, 0x4c, 0x4d, 0x4e, 0x4f, 0x50,
0x00, 0x00, 0x00, 0x00, // Size of Data (0)
];</pre></div>
</section>
</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><section id="references" class="appendix" typeof="bibo:Chapter" resource="#references" rel="bibo:Chapter"><!--OddPage--><h2 role="heading" id="h2_references"><span class="secno">A. </span>References</h2><section id="normative-references" typeof="bibo:Chapter" resource="#normative-references" rel="bibo:Chapter"><h3 role="heading" id="h3_normative-references"><span class="secno">A.1 </span>Normative references</h3><dl class="bibliography" about=""><dt id="bib-BMFF">[BMFF]</dt><dd rel="dcterms:requires"><a href="http://standards.iso.org/ittf/PubliclyAvailableStandards/c061988_ISO_IEC_14496-12_2012.zip"><cite>ISO/IEC 14496-12:2012, Information technology -- Coding of audio-visual objects -- Part 12: ISO base media file format</cite></a>. International Standard. URL: <a href="http://standards.iso.org/ittf/PubliclyAvailableStandards/c061988_ISO_IEC_14496-12_2012.zip">http://standards.iso.org/ittf/PubliclyAvailableStandards/c061988_ISO_IEC_14496-12_2012.zip</a>
</dd><dt id="bib-CENC-1ST">[CENC-1ST]</dt><dd rel="dcterms:requires"><a href="https://www.iso.org/obp/ui/#iso:std:iso-iec:23001:-7:ed-1:v1"><cite>ISO/IEC 23001-7:2012, Information technology -- MPEG systems technologies -- Part 7: Common encryption in ISO base media file format files</cite></a>. International Standard. URL: <a href="https://www.iso.org/obp/ui/#iso:std:iso-iec:23001:-7:ed-1:v1">https://www.iso.org/obp/ui/#iso:std:iso-iec:23001:-7:ed-1:v1</a>
</dd><dt id="bib-CENC-2ND">[CENC-2ND]</dt><dd rel="dcterms:requires"><cite>ISO/IEC DIS 23001-7 2nd Edition</cite>. Draft International Standard.
</dd></dl></section></section></body></html>