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<!DOCTYPE html><html dir="ltr" lang="en"><head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<meta name="generator" content="ReSpec 25.18.4">
<meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
<style>
.issue-label{text-transform:initial}
.warning>p:first-child{margin-top:0}
.warning{padding:.5em;border-left-width:.5em;border-left-style:solid}
span.warning{padding:.1em .5em .15em}
.issue.closed span.issue-number{text-decoration:line-through}
.warning{border-color:#f11;border-width:.2em;border-style:solid;background:#fbe9e9}
.warning-title:before{content:"⚠";font-size:1.3em;float:left;padding-right:.3em;margin-top:-.3em}
li.task-list-item{list-style:none}
input.task-list-item-checkbox{margin:0 .35em .25em -1.6em;vertical-align:middle}
.issue a.respec-gh-label{padding:5px;margin:0 2px 0 2px;font-size:10px;text-transform:none;text-decoration:none;font-weight:700;border-radius:4px;position:relative;bottom:2px;border:none;display:inline-block}
</style>
<style>
pre.idl{padding:1em;position:relative}
@media print{
pre.idl{white-space:pre-wrap}
}
.idlHeader{display:block;width:150px;background:#8ccbf2;color:#fff;font-family:sans-serif;font-weight:700;margin:-1em 0 1em -1em;height:28px;line-height:28px}
.idlHeader a.self-link{margin-left:.3cm;text-decoration:none;border-bottom:none}
.idlID{font-weight:700;color:#005a9c}
.idlType{color:#005a9c}
.idlName{color:#ff4500}
.idlName a{color:#ff4500;border-bottom:1px dotted #ff4500;text-decoration:none}
a.idlEnumItem{color:#000;border-bottom:1px dotted #ccc;text-decoration:none}
.idlSuperclass{font-style:italic;color:#005a9c}
.idlDefaultValue,.idlParamName{font-style:italic}
.extAttr{color:#666}
.idlSectionComment{color:gray}
.idlIncludes a{font-weight:700}
.respec-button-copy-paste:focus{text-decoration:none;border-color:#51a7e8;outline:0;box-shadow:0 0 5px rgba(81,167,232,.5)}
.respec-button-copy-paste.selected:focus,.respec-button-copy-paste:focus:hover{border-color:#51a7e8}
.respec-button-copy-paste.zeroclipboard-is-active,.respec-button-copy-paste.zeroclipboard-is-hover,.respec-button-copy-paste:active,.respec-button-copy-paste:hover{text-decoration:none;background-color:#ddd;background-image:linear-gradient(#eee,#ddd);border-color:#ccc}
.respec-button-copy-paste.selected,.respec-button-copy-paste.zeroclipboard-is-active,.respec-button-copy-paste:active{background-color:#dcdcdc;background-image:none;border-color:#b5b5b5;box-shadow:inset 0 2px 4px rgba(0,0,0,.15)}
.respec-button-copy-paste.selected:hover{background-color:#cfcfcf}
.respec-button-copy-paste.disabled,.respec-button-copy-paste.disabled:hover,.respec-button-copy-paste:disabled,.respec-button-copy-paste:disabled:hover{color:rgba(102,102,102,.5);cursor:default;background-color:rgba(229,229,229,.5);background-image:none;border-color:rgba(197,197,197,.5);box-shadow:none}
@media print{
.respec-button-copy-paste{visibility:hidden}
}
</style>
<style>
dfn{cursor:pointer}
.dfn-panel{position:absolute;z-index:35;min-width:300px;max-width:500px;padding:.5em .75em;margin-top:.6em;font:small Helvetica Neue,sans-serif,Droid Sans Fallback;background:#fff;color:#000;box-shadow:0 1em 3em -.4em rgba(0,0,0,.3),0 0 1px 1px rgba(0,0,0,.05);border-radius:2px}
.dfn-panel:not(.docked)>.caret{position:absolute;top:-9px}
.dfn-panel:not(.docked)>.caret::after,.dfn-panel:not(.docked)>.caret::before{content:"";position:absolute;border:10px solid transparent;border-top:0;border-bottom:10px solid #fff;top:0}
.dfn-panel:not(.docked)>.caret::before{border-bottom:9px solid #a2a9b1}
.dfn-panel *{margin:0}
.dfn-panel b{display:block;color:#000;margin-top:.25em}
.dfn-panel ul a[href]{color:#333}
.dfn-panel>div{display:flex}
.dfn-panel a.self-link{font-weight:700;margin-right:auto}
.dfn-panel .marker{padding:.1em;margin-left:.5em;border-radius:.2em;text-align:center;white-space:nowrap;font-size:90%;color:#040b1c}
.dfn-panel .marker.dfn-exported{background:#d1edfd;box-shadow:0 0 0 .125em #1ca5f940}
.dfn-panel .marker.idl-block{background:#8ccbf2;box-shadow:0 0 0 .125em #0670b161}
.dfn-panel a:not(:hover){text-decoration:none!important;border-bottom:none!important}
.dfn-panel a[href]:hover{border-bottom-width:1px}
.dfn-panel ul{padding:0}
.dfn-panel li{margin-left:1em}
.dfn-panel.docked{position:fixed;left:.5em;top:unset;bottom:2em;margin:0 auto;max-width:calc(100vw - .75em * 2 - .5em - .2em * 2);max-height:30vh;overflow:auto}
</style>
<title>Media Source Extensions™</title>
<style id="respec-mainstyle">
@keyframes pop{
0%{transform:scale(1,1)}
25%{transform:scale(1.25,1.25);opacity:.75}
100%{transform:scale(1,1)}
}
.hljs{background:0 0!important}
a abbr,h1 abbr,h2 abbr,h3 abbr,h4 abbr,h5 abbr,h6 abbr{border:none}
dfn{font-weight:700}
a.internalDFN{color:inherit;border-bottom:1px solid #99c;text-decoration:none}
a.externalDFN{color:inherit;border-bottom:1px dotted #ccc;text-decoration:none}
a.bibref{text-decoration:none}
.respec-offending-element:target{animation:pop .25s ease-in-out 0s 1}
.respec-offending-element,a[href].respec-offending-element{text-decoration:red wavy underline}
@supports not (text-decoration:red wavy underline){
.respec-offending-element:not(pre){display:inline-block}
.respec-offending-element{background:url(data:image/gif;base64,R0lGODdhBAADAPEAANv///8AAP///wAAACwAAAAABAADAEACBZQjmIAFADs=) bottom repeat-x}
}
#references :target{background:#eaf3ff;animation:pop .4s ease-in-out 0s 1}
cite .bibref{font-style:normal}
code{color:#c63501}
th code{color:inherit}
a[href].orcid{padding-left:4px;padding-right:4px}
a[href].orcid>svg{margin-bottom:-2px}
.toc a,.tof a{text-decoration:none}
a .figno,a .secno{color:#000}
ol.tof,ul.tof{list-style:none outside none}
.caption{margin-top:.5em;font-style:italic}
table.simple{border-spacing:0;border-collapse:collapse;border-bottom:3px solid #005a9c}
.simple th{background:#005a9c;color:#fff;padding:3px 5px;text-align:left}
.simple th a{color:#fff;padding:3px 5px;text-align:left}
.simple th[scope=row]{background:inherit;color:inherit;border-top:1px solid #ddd}
.simple td{padding:3px 10px;border-top:1px solid #ddd}
.simple tr:nth-child(even){background:#f0f6ff}
.section dd>p:first-child{margin-top:0}
.section dd>p:last-child{margin-bottom:0}
.section dd{margin-bottom:1em}
.section dl.attrs dd,.section dl.eldef dd{margin-bottom:0}
#issue-summary>ul{column-count:2}
#issue-summary li{list-style:none;display:inline-block}
details.respec-tests-details{margin-left:1em;display:inline-block;vertical-align:top}
details.respec-tests-details>*{padding-right:2em}
details.respec-tests-details[open]{z-index:999999;position:absolute;border:thin solid #cad3e2;border-radius:.3em;background-color:#fff;padding-bottom:.5em}
details.respec-tests-details[open]>summary{border-bottom:thin solid #cad3e2;padding-left:1em;margin-bottom:1em;line-height:2em}
details.respec-tests-details>ul{width:100%;margin-top:-.3em}
details.respec-tests-details>li{padding-left:1em}
a[href].self-link:hover{opacity:1;text-decoration:none;background-color:transparent}
h2,h3,h4,h5,h6{position:relative}
aside.example .marker>a.self-link{color:inherit}
h2>a.self-link,h3>a.self-link,h4>a.self-link,h5>a.self-link,h6>a.self-link{border:none;color:inherit;font-size:83%;height:2em;left:-1.6em;opacity:.5;position:absolute;text-align:center;text-decoration:none;top:0;transition:opacity .2s;width:2em}
h2>a.self-link::before,h3>a.self-link::before,h4>a.self-link::before,h5>a.self-link::before,h6>a.self-link::before{content:"§";display:block}
@media (max-width:767px){
dd{margin-left:0}
h2>a.self-link,h3>a.self-link,h4>a.self-link,h5>a.self-link,h6>a.self-link{left:auto;top:auto}
}
@media print{
.removeOnSave{display:none}
}
</style>
<script src="https://code.jquery.com/jquery-3.5.1.min.js" integrity="sha256-9/aliU8dGd2tb6OSsuzixeV4y/faTqgFtohetphbbj0=" crossorigin="anonymous"></script>
<link rel="stylesheet" href="mse.css">
<link rel="canonical" href="https://www.w3.org/TR/media-source/">
<style>
.hljs{display:block;overflow-x:auto;padding:.5em;color:#383a42;background:#fafafa}
.hljs-comment,.hljs-quote{color:#717277;font-style:italic}
.hljs-doctag,.hljs-formula,.hljs-keyword{color:#a626a4}
.hljs-deletion,.hljs-name,.hljs-section,.hljs-selector-tag,.hljs-subst{color:#ca4706;font-weight:700}
.hljs-literal{color:#0b76c5}
.hljs-addition,.hljs-attribute,.hljs-meta-string,.hljs-regexp,.hljs-string{color:#42803c}
.hljs-built_in,.hljs-class .hljs-title{color:#9a6a01}
.hljs-attr,.hljs-number,.hljs-selector-attr,.hljs-selector-class,.hljs-selector-pseudo,.hljs-template-variable,.hljs-type,.hljs-variable{color:#986801}
.hljs-bullet,.hljs-link,.hljs-meta,.hljs-selector-id,.hljs-symbol,.hljs-title{color:#336ae3}
.hljs-emphasis{font-style:italic}
.hljs-strong{font-weight:700}
.hljs-link{text-decoration:underline}
</style>
<style>
var{position:relative;cursor:pointer}
var[data-type]::after,var[data-type]::before{position:absolute;left:50%;top:-6px;opacity:0;transition:opacity .4s;pointer-events:none}
var[data-type]::before{content:"";transform:translateX(-50%);border-width:4px 6px 0 6px;border-style:solid;border-color:transparent;border-top-color:#000}
var[data-type]::after{content:attr(data-type);transform:translateX(-50%) translateY(-100%);background:#000;text-align:center;font-family:"Dank Mono","Fira Code",monospace;font-style:normal;padding:6px;border-radius:3px;color:#daca88;text-indent:0;font-weight:400}
var[data-type]:hover::after,var[data-type]:hover::before{opacity:1}
</style>
<script id="initialUserConfig" type="application/json">{
"specStatus": "ED",
"useExperimentalStyles": true,
"shortName": "media-source",
"edDraftURI": "https://w3c.github.io/media-source/",
"previousMaturity": "PR",
"previousPublishDate": "2016-10-04",
"errata": "https://w3c.github.io/media-source/mse-1-errata.html",
"editors": [
{
"name": "Matthew Wolenetz",
"url": "",
"company": "Google Inc.",
"companyURL": "http://www.google.com/"
},
{
"name": "Mark Watson",
"url": "",
"company": "Netflix Inc.",
"companyURL": "http://www.netflix.com/"
}
],
"formerEditors": [
{
"name": "Jerry Smith",
"note": "Until September 2017",
"url": "",
"company": "Microsoft Corporation",
"companyURL": "http://www.microsoft.com/"
},
{
"name": "Aaron Colwell",
"note": "Until April 2015",
"url": "",
"company": "Google Inc.",
"companyURL": "http://www.google.com/"
},
{
"name": "Adrian Bateman",
"note": "Until April 2015",
"url": "",
"company": "Microsoft Corporation",
"companyURL": "http://www.microsoft.com/"
}
],
"mseDefGroupName": "media-source",
"mseContributors": [
"Alex Giladi",
"Bob Lund",
"Chris Poole",
"Cyril Concolato",
"David Dorwin",
"David Singer",
"Duncan Rowden",
"Frank Galligan",
"Glenn Adams",
"Jer Noble",
"Joe Steele",
"John Simmons",
"Kevin Streeter",
"Mark Vickers",
"Matt Ward",
"Matthew Gregan",
"Michael Thornburgh",
"Philip Jägenstedt",
"Pierre Lemieux",
"Ralph Giles",
"Steven Robertson",
"Tatsuya Igarashi"
],
"group": "media",
"implementationReportURI": "https://tidoust.github.io/media-source-testcoverage/",
"scheme": "https",
"otherLinks": [
{
"key": "Repository",
"data": [
{
"value": "We are on GitHub",
"href": "https://github.com/w3c/media-source/"
},
{
"value": "File a bug",
"href": "https://github.com/w3c/media-source/issues"
},
{
"value": "Commit history",
"href": "https://github.com/w3c/media-source/commits/gh-pages/media-source-respec.html"
}
]
},
{
"key": "Mailing list",
"data": [
{
"value": "public-media-wg@w3.org",
"href": "https://lists.w3.org/Archives/Public/public-media-wg/"
}
]
},
{
"key": "Implementation",
"data": [
{
"value": "Can I use Media Source Extensions?",
"href": "http://caniuse.com/#feat=mediasource"
},
{
"value": "Test Suite",
"href": "http://w3c-test.org/media-source/"
},
{
"value": "Test Suite repository",
"href": "https://github.com/web-platform-tests/wpt/tree/master/media-source"
}
]
}
],
"preProcess": [
null
],
"postProcess": [
null
],
"publishISODate": "2020-11-25T00:00:00.000Z",
"generatedSubtitle": "Editor's Draft 25 November 2020"
}</script>
<link rel="stylesheet" href="https://www.w3.org/StyleSheets/TR/2016/W3C-ED"></head>
<body data-cite="WebIDL html dom url" class="h-entry"><div class="head">
<a class="logo" href="https://www.w3.org/"><img alt="W3C" src="https://www.w3.org/StyleSheets/TR/2016/logos/W3C" width="72" height="48"></a> <h1 id="title" class="title">Media Source Extensions™</h1>
<h2>
W3C Editor's Draft
<time class="dt-published" datetime="2020-11-25">25 November 2020</time>
</h2>
<dl>
<dt>This version:</dt><dd>
<a class="u-url" href="https://w3c.github.io/media-source/">https://w3c.github.io/media-source/</a>
</dd><dt>Latest published version:</dt><dd>
<a href="https://www.w3.org/TR/media-source/">https://www.w3.org/TR/media-source/</a>
</dd>
<dt>Latest editor's draft:</dt><dd><a href="https://w3c.github.io/media-source/">https://w3c.github.io/media-source/</a></dd>
<dt>Implementation report:</dt><dd>
<a href="https://tidoust.github.io/media-source-testcoverage/">https://tidoust.github.io/media-source-testcoverage/</a>
</dd>
<dt>Editors:</dt>
<dd class="p-author h-card vcard"><span class="p-name fn">Matthew Wolenetz</span>
(<a class="p-org org h-org h-card" href="http://www.google.com/">Google Inc.</a>)
</dd><dd class="p-author h-card vcard"><span class="p-name fn">Mark Watson</span>
(<a class="p-org org h-org h-card" href="http://www.netflix.com/">Netflix Inc.</a>)
</dd>
<dt>
Former editors:
</dt><dd class="p-author h-card vcard"><span class="p-name fn">Jerry Smith</span>
(<a class="p-org org h-org h-card" href="http://www.microsoft.com/">Microsoft Corporation</a>)
(Until September 2017)</dd><dd class="p-author h-card vcard"><span class="p-name fn">Aaron Colwell</span>
(<a class="p-org org h-org h-card" href="http://www.google.com/">Google Inc.</a>)
(Until April 2015)</dd><dd class="p-author h-card vcard"><span class="p-name fn">Adrian Bateman</span>
(<a class="p-org org h-org h-card" href="http://www.microsoft.com/">Microsoft Corporation</a>)
(Until April 2015)</dd>
<dt>Repository:</dt><dd>
<a href="https://github.com/w3c/media-source/">We are on GitHub</a>
</dd><dd>
<a href="https://github.com/w3c/media-source/issues">File a bug</a>
</dd><dd>
<a href="https://github.com/w3c/media-source/commits/gh-pages/media-source-respec.html">Commit history</a>
</dd><dt>Mailing list:</dt><dd>
<a href="https://lists.w3.org/Archives/Public/public-media-wg/">public-media-wg@w3.org</a>
</dd><dt>Implementation:</dt><dd>
<a href="http://caniuse.com/#feat=mediasource">Can I use Media Source Extensions?</a>
</dd><dd>
<a href="http://w3c-test.org/media-source/">Test Suite</a>
</dd><dd>
<a href="https://github.com/web-platform-tests/wpt/tree/master/media-source">Test Suite repository</a>
</dd>
</dl>
<p>
Please check the
<a href="https://w3c.github.io/media-source/mse-1-errata.html"><strong>errata</strong></a> for any errors or
issues reported since publication.
</p>
<p class="copyright">
<a href="https://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a>
©
2020
<a href="https://www.w3.org/"><abbr title="World Wide Web Consortium">W3C</abbr></a><sup>®</sup> (<a href="https://www.csail.mit.edu/"><abbr title="Massachusetts Institute of Technology">MIT</abbr></a>,
<a href="https://www.ercim.eu/"><abbr title="European Research Consortium for Informatics and Mathematics">ERCIM</abbr></a>, <a href="https://www.keio.ac.jp/">Keio</a>,
<a href="https://ev.buaa.edu.cn/">Beihang</a>).
W3C <a href="https://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>,
<a href="https://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a> and <a rel="license" href="https://www.w3.org/Consortium/Legal/2015/copyright-software-and-document">permissive document license</a> rules
apply.
</p>
<hr title="Separator for header">
</div>
<section id="sotd" class="introductory"><h2>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="https://www.w3.org/TR/"><abbr title="World Wide Web Consortium">W3C</abbr> technical reports index</a> at
https://www.w3.org/TR/.</em></p>
<p>The working group maintains <a href="https://github.com/w3c/media-source/issues">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 track the <a href="https://github.com/w3c/media-source">GitHub repository</a> and take part in the discussions.</p>
<p>
This document was published by the <a href="https://www.w3.org/media-wg/">Media Working Group</a> as an
Editor's Draft.
</p><p>
Publication as an Editor's Draft does not imply endorsement
by the <abbr title="World Wide Web Consortium">W3C</abbr> Membership.
</p><p>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></p><p>
This document was produced by a group
operating under the
<a href="https://www.w3.org/Consortium/Patent-Policy-20170801/">1 August 2017 <abbr title="World Wide Web Consortium">W3C</abbr> Patent
Policy</a>.
<abbr title="World Wide Web Consortium">W3C</abbr> maintains a
<a rel="disclosure" href="https://www.w3.org/2004/01/pp-impl/115198/status">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="https://www.w3.org/Consortium/Patent-Policy-20170801/#def-essential">Essential Claim(s)</a>
must disclose the information in accordance with
<a href="https://www.w3.org/Consortium/Patent-Policy-20170801/#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="https://www.w3.org/2020/Process-20200915/">15 September 2020 <abbr title="World Wide Web Consortium">W3C</abbr> Process Document</a>.
</p></section><nav id="toc"><h2 class="introductory" id="table-of-contents">Table of Contents</h2><ol class="toc"><li class="tocline"><a class="tocxref" href="#introduction"><bdi class="secno">1. </bdi>Introduction</a><ol class="toc"><li class="tocline"><a class="tocxref" href="#goals"><bdi class="secno">1.1 </bdi>Goals</a></li><li class="tocline"><a class="tocxref" href="#definitions"><bdi class="secno">1.2 </bdi>Definitions</a></li></ol></li><li class="tocline"><a class="tocxref" href="#mediasource"><bdi class="secno">2. </bdi><span data-export="" data-dfn-type="interface" data-idl="interface" data-title="MediaSource" data-dfn-for=""><code>MediaSource</code></span> Object</a><ol class="toc"><li class="tocline"><a class="tocxref" href="#attributes"><bdi class="secno">2.1 </bdi>Attributes</a></li><li class="tocline"><a class="tocxref" href="#methods"><bdi class="secno">2.2 </bdi>Methods</a></li><li class="tocline"><a class="tocxref" href="#mediasource-events"><bdi class="secno">2.3 </bdi>Event Summary</a></li><li class="tocline"><a class="tocxref" href="#mediasource-algorithms"><bdi class="secno">2.4 </bdi>Algorithms</a><ol class="toc"><li class="tocline"><a class="tocxref" href="#mediasource-attach"><bdi class="secno">2.4.1 </bdi>Attaching to a media element</a></li><li class="tocline"><a class="tocxref" href="#mediasource-detach"><bdi class="secno">2.4.2 </bdi>Detaching from a media element</a></li><li class="tocline"><a class="tocxref" href="#mediasource-seeking"><bdi class="secno">2.4.3 </bdi>Seeking</a></li><li class="tocline"><a class="tocxref" href="#buffer-monitoring"><bdi class="secno">2.4.4 </bdi>SourceBuffer Monitoring</a></li><li class="tocline"><a class="tocxref" href="#active-source-buffer-changes"><bdi class="secno">2.4.5 </bdi>Changes to selected/enabled track state</a></li><li class="tocline"><a class="tocxref" href="#duration-change-algorithm"><bdi class="secno">2.4.6 </bdi>Duration change</a></li><li class="tocline"><a class="tocxref" href="#end-of-stream-algorithm"><bdi class="secno">2.4.7 </bdi>End of stream algorithm</a></li></ol></li></ol></li><li class="tocline"><a class="tocxref" href="#sourcebuffer"><bdi class="secno">3. </bdi><span data-export="" data-dfn-type="interface" data-idl="interface" data-title="SourceBuffer" data-dfn-for=""><code>SourceBuffer</code></span> Object</a><ol class="toc"><li class="tocline"><a class="tocxref" href="#attributes-0"><bdi class="secno">3.1 </bdi>Attributes</a></li><li class="tocline"><a class="tocxref" href="#methods-0"><bdi class="secno">3.2 </bdi>Methods</a></li><li class="tocline"><a class="tocxref" href="#track-buffers"><bdi class="secno">3.3 </bdi>Track Buffers</a></li><li class="tocline"><a class="tocxref" href="#sourcebuffer-events"><bdi class="secno">3.4 </bdi>Event Summary</a></li><li class="tocline"><a class="tocxref" href="#sourcebuffer-algorithms"><bdi class="secno">3.5 </bdi>Algorithms</a><ol class="toc"><li class="tocline"><a class="tocxref" href="#sourcebuffer-segment-parser-loop"><bdi class="secno">3.5.1 </bdi>Segment Parser Loop</a></li><li class="tocline"><a class="tocxref" href="#sourcebuffer-reset-parser-state"><bdi class="secno">3.5.2 </bdi>Reset Parser State</a></li><li class="tocline"><a class="tocxref" href="#sourcebuffer-append-error"><bdi class="secno">3.5.3 </bdi>Append Error Algorithm</a></li><li class="tocline"><a class="tocxref" href="#sourcebuffer-prepare-append"><bdi class="secno">3.5.4 </bdi>Prepare Append Algorithm</a></li><li class="tocline"><a class="tocxref" href="#sourcebuffer-buffer-append"><bdi class="secno">3.5.5 </bdi>Buffer Append Algorithm</a></li><li class="tocline"><a class="tocxref" href="#sourcebuffer-range-removal"><bdi class="secno">3.5.6 </bdi>Range Removal</a></li><li class="tocline"><a class="tocxref" href="#sourcebuffer-init-segment-received"><bdi class="secno">3.5.7 </bdi>Initialization Segment Received</a></li><li class="tocline"><a class="tocxref" href="#sourcebuffer-coded-frame-processing"><bdi class="secno">3.5.8 </bdi>Coded Frame Processing</a></li><li class="tocline"><a class="tocxref" href="#sourcebuffer-coded-frame-removal"><bdi class="secno">3.5.9 </bdi>Coded Frame Removal Algorithm</a></li><li class="tocline"><a class="tocxref" href="#sourcebuffer-coded-frame-eviction"><bdi class="secno">3.5.10 </bdi>Coded Frame Eviction Algorithm</a></li><li class="tocline"><a class="tocxref" href="#sourcebuffer-audio-splice-frame-algorithm"><bdi class="secno">3.5.11 </bdi>Audio Splice Frame Algorithm</a></li><li class="tocline"><a class="tocxref" href="#sourcebuffer-audio-splice-rendering-algorithm"><bdi class="secno">3.5.12 </bdi>Audio Splice Rendering Algorithm</a></li><li class="tocline"><a class="tocxref" href="#sourcebuffer-text-splice-frame-algorithm"><bdi class="secno">3.5.13 </bdi>Text Splice Frame Algorithm</a></li></ol></li></ol></li><li class="tocline"><a class="tocxref" href="#sourcebufferlist"><bdi class="secno">4. </bdi><span data-export="" data-dfn-type="interface" data-idl="interface" data-title="SourceBufferList" data-dfn-for=""><code>SourceBufferList</code></span> Object</a><ol class="toc"><li class="tocline"><a class="tocxref" href="#attributes-1"><bdi class="secno">4.1 </bdi>Attributes</a></li><li class="tocline"><a class="tocxref" href="#methods-1"><bdi class="secno">4.2 </bdi>Methods</a></li><li class="tocline"><a class="tocxref" href="#sourcebufferlist-events"><bdi class="secno">4.3 </bdi>Event Summary</a></li></ol></li><li class="tocline"><a class="tocxref" href="#url"><bdi class="secno">5. </bdi>URL Object Extensions</a><ol class="toc"><li class="tocline"><a class="tocxref" href="#methods-2"><bdi class="secno">5.1 </bdi>Methods</a></li></ol></li><li class="tocline"><a class="tocxref" href="#htmlmediaelement-extensions"><bdi class="secno">6. </bdi>HTMLMediaElement Extensions</a></li><li class="tocline"><a class="tocxref" href="#audio-track-extensions"><bdi class="secno">7. </bdi>AudioTrack Extensions</a></li><li class="tocline"><a class="tocxref" href="#video-track-extensions"><bdi class="secno">8. </bdi>VideoTrack Extensions</a></li><li class="tocline"><a class="tocxref" href="#text-track-extensions"><bdi class="secno">9. </bdi>TextTrack Extensions</a></li><li class="tocline"><a class="tocxref" href="#byte-stream-formats"><bdi class="secno">10. </bdi>Byte Stream Formats</a></li><li class="tocline"><a class="tocxref" href="#conformance"><bdi class="secno">11. </bdi>Conformance</a></li><li class="tocline"><a class="tocxref" href="#examples"><bdi class="secno">12. </bdi>Examples</a></li><li class="tocline"><a class="tocxref" href="#acknowledgements"><bdi class="secno">13. </bdi>Acknowledgments</a></li><li class="tocline"><a class="tocxref" href="#VideoPlaybackQuality"><bdi class="secno">A. </bdi>VideoPlaybackQuality</a></li><li class="tocline"><a class="tocxref" href="#references"><bdi class="secno">B. </bdi>References</a><ol class="toc"><li class="tocline"><a class="tocxref" href="#normative-references"><bdi class="secno">B.1 </bdi>Normative references</a></li><li class="tocline"><a class="tocxref" href="#informative-references"><bdi class="secno">B.2 </bdi>Informative references</a></li></ol></li></ol></nav>
<section id="abstract" class="introductory"><h2>Abstract</h2>
This specification extends <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#htmlmediaelement-htmlmediaelement">HTMLMediaElement</a></code> [<cite><a class="bibref" data-link-type="biblio" href="#bib-html" title="HTML Standard">HTML</a></cite>] to allow
JavaScript to generate media streams for playback.
Allowing JavaScript to generate streams facilitates a variety of use
cases like adaptive streaming and time shifting live streams.
</section>
<section id="introduction" class="informative">
<h2 id="x1-introduction"><bdi class="secno">1. </bdi>Introduction<a class="self-link" aria-label="§" href="#introduction"></a></h2><p><em>This section is non-normative.</em></p>
<p>This specification allows JavaScript to dynamically construct media streams for <audio> and <video>. It defines a MediaSource object that can serve as a source of media data for an HTMLMediaElement. MediaSource objects have one or more <a href="#dom-sourcebuffer" class="internalDFN" data-link-type="idl" id="ref-for-dom-sourcebuffer-1"><code>SourceBuffer</code></a> objects. Applications append data segments to the <a href="#dom-sourcebuffer" class="internalDFN" data-link-type="idl" id="ref-for-dom-sourcebuffer-2"><code>SourceBuffer</code></a> objects, and can adapt the quality of appended data based on system performance and other factors. Data from the <a href="#dom-sourcebuffer" class="internalDFN" data-link-type="idl" id="ref-for-dom-sourcebuffer-3"><code>SourceBuffer</code></a> objects is managed as track buffers for audio, video and text data that is decoded and played. Byte stream specifications used with these extensions are available in the byte stream format registry [<cite><a class="bibref" data-link-type="biblio" href="#bib-mse-registry" title="Media Source Extensions™ Byte Stream Format Registry">MSE-REGISTRY</a></cite>].</p>
<img src="pipeline_model.svg" alt="Media Source Pipeline Model Diagram" longdesc="pipeline_model_description.html#pipelinedesc">
<section id="goals">
<h3 id="x1-1-goals"><bdi class="secno">1.1 </bdi>Goals<a class="self-link" aria-label="§" href="#goals"></a></h3>
<p>This specification was designed with the following goals in mind:</p>
<ul>
<li>Allow JavaScript to construct media streams independent of how the media is fetched.</li>
<li>Define a splicing and buffering model that facilitates use cases like adaptive streaming, ad-insertion, time-shifting, and video editing.</li>
<li>Minimize the need for media parsing in JavaScript.</li>
<li>Leverage the browser cache as much as possible.</li>
<li>Provide requirements for byte stream format specifications.</li>
<li>Not require support for any particular media format or codec.</li>
</ul>
<p>This specification defines:</p>
<ul>
<li>Normative behavior for user agents to enable interoperability between user agents and web applications when processing media data.</li>
<li>Normative requirements to enable other specifications to define media formats to be used within this specification.</li>
</ul>
</section>
<section id="definitions">
<h3 id="x1-2-definitions"><bdi class="secno">1.2 </bdi>Definitions<a class="self-link" aria-label="§" href="#definitions"></a></h3>
<dl>
<dt id="active-track-buffers">Active Track Buffers</dt>
<dd><p>The <a href="#track-buffer">track buffers</a> that provide <a href="#coded-frame">coded frames</a> for the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-audiotrack-enabled">enabled</a></code>
<code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-audiotracks">audioTracks</a></code>, the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-videotrack-selected">selected</a></code> <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-videotracks">videoTracks</a></code>, and the
<code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-texttrackmode-showing">"showing"</a></code> or <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-texttrackmode-hidden">"hidden"</a></code> <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-texttracks">textTracks</a></code>. All these tracks are associated with
<a href="#dom-sourcebuffer" class="internalDFN" data-link-type="idl" id="ref-for-dom-sourcebuffer-4"><code>SourceBuffer</code></a> objects in the <code><a href="#dom-mediasource-activesourcebuffers">activeSourceBuffers</a></code> list.</p>
</dd>
<dt id="append-window">Append Window</dt>
<dd><p>A <a href="#presentation-timestamp">presentation timestamp</a> range used to filter out <a href="#coded-frame">coded frames</a> while appending. The append window represents a single
continuous time range with a single start time and end time. Coded frames with <a href="#presentation-timestamp">presentation timestamp</a> within this range are allowed to be appended
to the <a href="#dom-sourcebuffer" class="internalDFN" data-link-type="idl" id="ref-for-dom-sourcebuffer-5"><code>SourceBuffer</code></a> while coded frames outside this range are filtered out. The append window start and end times are controlled by
the <code><a href="#dom-sourcebuffer-appendwindowstart">appendWindowStart</a></code> and <code><a href="#dom-sourcebuffer-appendwindowend">appendWindowEnd</a></code> attributes respectively.</p></dd>
<dt id="coded-frame">Coded Frame</dt>
<dd><p>A unit of media data that has a <a href="#presentation-timestamp">presentation timestamp</a>, a <a href="#decode-timestamp">decode timestamp</a>, and a <a href="#coded-frame-duration">coded frame duration</a>.</p></dd>
<dt id="coded-frame-duration">Coded Frame Duration</dt>
<dd>
<p>The duration of a <a href="#coded-frame">coded frame</a>. For video and text, the duration indicates how long the video frame or text <em class="rfc2119">SHOULD</em> be displayed. For audio, the duration represents the sum of all the samples contained within the coded frame. For example, if an audio frame contained 441 samples @44100Hz the frame duration would be 10 milliseconds.</p>
</dd>
<dt id="coded-frame-end-timestamp">Coded Frame End Timestamp</dt>
<dd>
<p>The sum of a <a href="#coded-frame">coded frame</a> <a href="#presentation-timestamp">presentation timestamp</a> and its
<a href="#coded-frame-duration">coded frame duration</a>. It represents the <a href="#presentation-timestamp">presentation timestamp</a> that immediately follows the coded frame.</p>
</dd>
<dt id="coded-frame-group">Coded Frame Group</dt>
<dd><p>A group of <a href="#coded-frame">coded frames</a> that are adjacent and have monotonically increasing <a href="#decode-timestamp">decode timestamps</a> without any gaps. Discontinuities detected by the
<a href="#sourcebuffer-coded-frame-processing">coded frame processing algorithm</a> and <code><a href="#dom-sourcebuffer-abort">abort()</a></code> calls trigger the start of a new coded frame group.</p>
</dd>
<dt id="decode-timestamp">Decode Timestamp</dt>
<dd>
<p> The decode timestamp indicates the latest time at which the frame needs to be decoded assuming instantaneous decoding and rendering of this and any dependant frames (this is equal to the <a href="#presentation-timestamp">presentation timestamp</a> of the earliest frame, in <a href="#presentation-order">presentation order</a>, that is dependant on this frame). If frames can be decoded out of <a href="#presentation-order">presentation order</a>, then the decode timestamp <em class="rfc2119">MUST</em> be present in or derivable from the byte stream. The user agent <em class="rfc2119">MUST</em> run the <a href="#sourcebuffer-append-error">append error algorithm</a> if this is not the case. If frames cannot be decoded out of <a href="#presentation-order">presentation order</a> and a decode timestamp is not present in the byte stream, then the decode timestamp is equal to the <a href="#presentation-timestamp">presentation timestamp</a>.</p>
</dd>
<dt id="init-segment">Initialization Segment</dt>
<dd>
<p>A sequence of bytes that contain all of the initialization information required to decode a sequence of <a href="#media-segment">media segments</a>. This includes codec initialization data, <a href="#track-id">Track ID</a> mappings for multiplexed segments, and timestamp offsets (e.g., edit lists).</p>
<div class="note" role="note" id="issue-container-generatedID"><div role="heading" class="note-title marker" id="h-note" aria-level="4"><span>Note</span></div><p class="">The <a href="#byte-stream-format-specs">byte stream format specifications</a> in the byte stream format registry [<cite><a class="bibref" data-link-type="biblio" href="#bib-mse-registry" title="Media Source Extensions™ Byte Stream Format Registry">MSE-REGISTRY</a></cite>] contain format specific examples.</p></div>
</dd><dt id="media-segment">Media Segment</dt>
<dd>
<p>A sequence of bytes that contain packetized & timestamped media data for a portion of the <a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#media-timeline">media timeline</a>. Media segments are always associated with the most recently appended <a href="#init-segment">initialization segment</a>.</p>
<div class="note" role="note" id="issue-container-generatedID-0"><div role="heading" class="note-title marker" id="h-note-0" aria-level="4"><span>Note</span></div><p class="">The <a href="#byte-stream-format-specs">byte stream format specifications</a> in the byte stream format registry [<cite><a class="bibref" data-link-type="biblio" href="#bib-mse-registry" title="Media Source Extensions™ Byte Stream Format Registry">MSE-REGISTRY</a></cite>] contain format specific examples.</p></div>
</dd>
<dt id="mediasource-object-url">MediaSource object URL</dt>
<dd>
<p>A MediaSource object URL is a unique <a href="https://www.w3.org/TR/FileAPI/#url">Blob URI</a> [<cite><a class="bibref" data-link-type="biblio" href="#bib-file-api" title="File API">FILE-API</a></cite>] created by <code><a href="#dom-url-createobjecturl">createObjectURL()</a></code>. It is used to attach a <a href="#dom-mediasource" class="internalDFN" data-link-type="idl" id="ref-for-dom-mediasource-1"><code>MediaSource</code></a> object to an HTMLMediaElement.</p>
<p>These URLs are the same as a <a href="https://www.w3.org/TR/FileAPI/#url">Blob URI</a>, except that anything in the definition of that feature that refers to <a href="https://www.w3.org/TR/FileAPI/#dfn-file">File</a> and <a href="https://www.w3.org/TR/FileAPI/#dfn-Blob">Blob</a> objects is hereby extended to also apply to <a href="#dom-mediasource" class="internalDFN" data-link-type="idl" id="ref-for-dom-mediasource-2"><code>MediaSource</code></a> objects.</p>
<p>The <a href="https://www.w3.org/TR/html51/browsers.html#section-origin">origin</a> of the MediaSource object URL is the <a href="https://www.w3.org/TR/html51/webappapis.html#relevant-settings-object">relevant settings object</a> of <code>this</code> during the call to <code><a href="#dom-url-createobjecturl">createObjectURL()</a></code>.</p>
<div class="note" role="note" id="issue-container-generatedID-1"><div role="heading" class="note-title marker" id="h-note-1" aria-level="4"><span>Note</span></div><p class="">For example, the <a href="https://www.w3.org/TR/html51/browsers.html#section-origin">origin</a> of the MediaSource object URL affects the way that the media element is <a href="https://html.spec.whatwg.org/multipage/canvas.html#security-with-canvas-elements">consumed by canvas</a>.</p></div>
</dd>
<dt id="parent-media-source">Parent Media Source</dt>
<dd><p>The parent media source of a <a href="#dom-sourcebuffer" class="internalDFN" data-link-type="idl" id="ref-for-dom-sourcebuffer-6"><code>SourceBuffer</code></a> object is the <a href="#dom-mediasource" class="internalDFN" data-link-type="idl" id="ref-for-dom-mediasource-3"><code>MediaSource</code></a> object that created it.</p></dd>
<dt id="presentation-start-time">Presentation Start Time</dt>
<dd><p>The presentation start time is the earliest time point in the presentation and specifies the <a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#initial-playback-position">initial playback position</a> and <a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#earliest-possible-position">earliest possible position</a>. All presentations created using this specification have a presentation start time of 0.</p>
<div class="note" role="note" id="issue-container-generatedID-2"><div role="heading" class="note-title marker" id="h-note-2" aria-level="4"><span>Note</span></div><p class="">For the purposes of determining if <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-buffered">HTMLMediaElement.buffered</a></code> contains a <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#timeranges-timeranges">TimeRange</a></code> that includes the current playback position, implementations <em class="rfc2119">MAY</em> choose to allow a current playback position at or after <a href="#presentation-start-time">presentation start time</a> and before the first <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#timeranges-timeranges">TimeRange</a></code> to play the first <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#timeranges-timeranges">TimeRange</a></code> if that <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#timeranges-timeranges">TimeRange</a></code> starts within a reasonably short time, like 1 second, after <a href="#presentation-start-time">presentation start time</a>. This allowance accommodates the reality that muxed streams commonly do not begin all tracks precisely at <a href="#presentation-start-time">presentation start time</a>. Implementations <em class="rfc2119">MUST</em> report the actual buffered range, regardless of this allowance.</p></div>
</dd>
<dt id="presentation-interval">Presentation Interval</dt>
<dd>
<p>The presentation interval of a <a href="#coded-frame">coded frame</a> is the time interval from its <a href="#presentation-timestamp">presentation timestamp</a> to the <a href="#presentation-timestamp">presentation timestamp</a> plus the <a href="#coded-frame-duration">coded frame's duration</a>. For example, if a coded frame has a presentation timestamp of 10 seconds and a <a href="#coded-frame-duration">coded frame duration</a> of 100 milliseconds, then the presentation interval would be [10-10.1). Note that the start of the range is inclusive, but the end of the range is exclusive.</p>
</dd>
<dt id="presentation-order">Presentation Order</dt>
<dd>
<p>The order that <a href="#coded-frame">coded frames</a> are rendered in the presentation. The presentation order is achieved by ordering <a href="#coded-frame">coded frames</a> in monotonically increasing order by their <a href="#presentation-timestamp">presentation timestamps</a>.</p>
</dd>
<dt id="presentation-timestamp">Presentation Timestamp</dt>
<dd>
<p>A reference to a specific time in the presentation. The presentation timestamp in a <a href="#coded-frame">coded frame</a> indicates when the frame <em class="rfc2119">SHOULD</em> be rendered.</p>
</dd>
<dt id="random-access-point">Random Access Point</dt>
<dd><p>A position in a <a href="#media-segment">media segment</a> where decoding and continuous playback can begin without relying on any previous data in the segment. For video this tends to be the location of I-frames. In the case of audio, most audio frames can be treated as a random access point. Since video tracks tend to have a more sparse distribution of random access points, the location of these points are usually considered the random access points for multiplexed streams.</p></dd>
<dt id="sourcebuffer-byte-stream-format-spec">SourceBuffer byte stream format specification</dt>
<dd><p>The specific <a href="#byte-stream-format-specs">byte stream format specification</a> that describes the format of the byte stream accepted by a <a href="#dom-sourcebuffer" class="internalDFN" data-link-type="idl" id="ref-for-dom-sourcebuffer-7"><code>SourceBuffer</code></a> instance. The
<a href="#byte-stream-format-specs">byte stream format specification</a>, for a <a href="#dom-sourcebuffer" class="internalDFN" data-link-type="idl" id="ref-for-dom-sourcebuffer-8"><code>SourceBuffer</code></a> object, is selected based on the <var>type</var> passed to the
<code><a href="#dom-mediasource-addsourcebuffer">addSourceBuffer()</a></code> call that created the object.</p></dd>
<dt id="sourcebuffer-configuration">SourceBuffer configuration</dt>
<dd><p>A specific set of tracks distributed across one or more <a href="#dom-sourcebuffer" class="internalDFN" data-link-type="idl" id="ref-for-dom-sourcebuffer-9"><code>SourceBuffer</code></a>
objects owned by a single <a href="#dom-mediasource" class="internalDFN" data-link-type="idl" id="ref-for-dom-mediasource-4"><code>MediaSource</code></a> instance.</p>
<p>Implementations <em class="rfc2119">MUST</em> support at least 1 <a href="#dom-mediasource" class="internalDFN" data-link-type="idl" id="ref-for-dom-mediasource-5"><code>MediaSource</code></a> object with the following
configurations:</p>
<ul>
<li>A single SourceBuffer with 1 audio track and/or 1 video track.</li>
<li>Two SourceBuffers with one handling a single audio track and the other handling a single video track.</li>
</ul>
<p>MediaSource objects <em class="rfc2119">MUST</em> support each of the configurations above, but they are only
required to support one configuration at a time. Supporting multiple configurations at once
or additional configurations is a quality of implementation issue.</p>
</dd>
<dt id="track-description">Track Description</dt>
<dd><p>A byte stream format specific structure that provides the <a href="#track-id">Track ID</a>, codec configuration, and other metadata for a single track. Each track description inside a single <a href="#init-segment">initialization segment</a> has a unique <a href="#track-id">Track ID</a>. The user agent <em class="rfc2119">MUST</em> run the <a href="#sourcebuffer-append-error">append error algorithm</a> if the <a href="#track-id">Track ID</a> is not unique within the <a href="#init-segment">initialization segment</a>.</p></dd>
<dt id="track-id">Track ID</dt>
<dd><p>A Track ID is a byte stream format specific identifier that marks sections of the byte stream as being part of a specific track. The Track ID in a <a href="#track-description">track description</a> identifies which sections of a <a href="#media-segment">media segment</a> belong to that track.</p></dd>
</dl>
</section>
</section>
<section id="mediasource">
<h2 id="x2-mediasource-object"><bdi class="secno">2. </bdi><dfn data-export="" data-dfn-type="interface" id="dom-mediasource" data-idl="interface" data-title="MediaSource" data-dfn-for=""><code>MediaSource</code></dfn> Object<a class="self-link" aria-label="§" href="#mediasource"></a></h2>
<p>The MediaSource object represents a source of media data for an HTMLMediaElement. It keeps track of the <a data-link-type="idl" href="#dom-mediasource-readystate" class="internalDFN" id="ref-for-dom-mediasource-readystate-1"><code><code>readyState</code></code></a> for this source as well as a list of <a href="#dom-sourcebuffer" class="internalDFN" data-link-type="idl" id="ref-for-dom-sourcebuffer-10"><code>SourceBuffer</code></a> objects that can be used to add media data to the presentation. MediaSource objects are created by the web application and then attached to an HTMLMediaElement. The application uses the <a href="#dom-sourcebuffer" class="internalDFN" data-link-type="idl" id="ref-for-dom-sourcebuffer-11"><code>SourceBuffer</code></a> objects in <code><a href="#dom-mediasource-sourcebuffers">sourceBuffers</a></code> to add media data to this source. The HTMLMediaElement fetches this media data from the <a href="#dom-mediasource" class="internalDFN" data-link-type="idl" id="ref-for-dom-mediasource-6"><code>MediaSource</code></a> object when it is needed during playback.</p>
<p>Each <a href="#dom-mediasource" class="internalDFN" data-link-type="idl" id="ref-for-dom-mediasource-7"><code>MediaSource</code></a> object has a <dfn id="live-seekable-range">live seekable range</dfn> variable that stores a <a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#normalized-timeranges-object">normalized TimeRanges object</a>. This variable is initialized to an empty <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#timeranges-timeranges">TimeRanges</a></code> object when the <a href="#dom-mediasource" class="internalDFN" data-link-type="idl" id="ref-for-dom-mediasource-8"><code>MediaSource</code></a> object is created, is maintained by <code><a href="#dom-mediasource-setliveseekablerange">setLiveSeekableRange()</a></code> and <code><a href="#dom-mediasource-clearliveseekablerange">clearLiveSeekableRange()</a></code>, and is used in <a href="#htmlmediaelement-extensions">HTMLMediaElement Extensions</a> to modify <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-seekable">HTMLMediaElement.seekable</a></code> behavior.</p>
<div><pre class="idl def" id="webidl-1246068066"><span class="idlHeader"><a class="self-link" href="#webidl-1246068066">WebIDL</a></span><span data-idl="" class="idlEnum" id="idl-def-readystate" data-title="ReadyState">enum <dfn data-export="" data-dfn-type="enum" id="dom-readystate" data-idl="enum" data-title="ReadyState" data-dfn-for="ReadyState" class="idlID"><code>ReadyState</code></dfn> {
<span class="idlEnumItem">"<a class="internalDFN" data-link-type="enum-value" href="#dom-readystate-closed" id="ref-for-dom-readystate-closed-1"><code>closed</code></a>"</span>,
<span class="idlEnumItem">"<a class="internalDFN" data-link-type="enum-value" href="#dom-readystate-open" id="ref-for-dom-readystate-open-1"><code>open</code></a>"</span>,
<span class="idlEnumItem">"<a class="internalDFN" data-link-type="enum-value" href="#dom-readystate-ended" id="ref-for-dom-readystate-ended-1"><code>ended</code></a>"</span>
};</span></pre><table class="simple" data-dfn-for="ReadyState" data-link-for="ReadyState"><tbody><tr><th colspan="2">Enumeration description</th></tr><tr><td><dfn data-export="" data-dfn-type="enum-value" id="dom-readystate-closed" data-idl="enum-value" data-title="closed" data-dfn-for="ReadyState"><code id="idl-def-ReadyState.closed">closed</code></dfn></td><td>
Indicates the source is not currently attached to a media element.
</td></tr><tr><td><dfn data-export="" data-dfn-type="enum-value" id="dom-readystate-open" data-idl="enum-value" data-title="open" data-dfn-for="ReadyState"><code id="idl-def-ReadyState.open">open</code></dfn></td><td>
The source has been opened by a media element and is ready for data to be appended to the <a href="#dom-sourcebuffer" class="internalDFN" data-link-type="idl" id="ref-for-dom-sourcebuffer-12"><code>SourceBuffer</code></a> objects in <code><a href="#dom-mediasource-sourcebuffers">sourceBuffers</a></code>.
</td></tr><tr><td><dfn data-export="" data-dfn-type="enum-value" id="dom-readystate-ended" data-idl="enum-value" data-title="ended" data-dfn-for="ReadyState"><code id="idl-def-ReadyState.ended">ended</code></dfn></td><td>
The source is still attached to a media element, but <code><a href="#dom-mediasource-endofstream">endOfStream()</a></code> has been called.
</td></tr></tbody></table></div>
<div><pre class="idl def" id="webidl-1490762926"><span class="idlHeader"><a class="self-link" href="#webidl-1490762926">WebIDL</a></span><span data-idl="" class="idlEnum" id="idl-def-endofstreamerror" data-title="EndOfStreamError">enum <dfn data-export="" data-dfn-type="enum" id="dom-endofstreamerror" data-idl="enum" data-title="EndOfStreamError" data-dfn-for="EndOfStreamError" class="idlID"><code>EndOfStreamError</code></dfn> {
<span class="idlEnumItem">"<a class="internalDFN" data-link-type="enum-value" href="#dom-endofstreamerror-network" id="ref-for-dom-endofstreamerror-network-1"><code>network</code></a>"</span>,
<span class="idlEnumItem">"<a class="internalDFN" data-link-type="enum-value" href="#dom-endofstreamerror-decode" id="ref-for-dom-endofstreamerror-decode-1"><code>decode</code></a>"</span>
};</span></pre><table class="simple" data-dfn-for="EndOfStreamError" data-link-for="EndOfStreamError"><tbody><tr><th colspan="2">Enumeration description</th></tr><tr><td><dfn data-export="" data-dfn-type="enum-value" id="dom-endofstreamerror-network" data-idl="enum-value" data-title="network" data-dfn-for="EndOfStreamError"><code id="idl-def-EndOfStreamError.network">network</code></dfn></td><td>
<p>Terminates playback and signals that a network error has occured.</p>
<div class="note" role="note" id="issue-container-generatedID-3"><div role="heading" class="note-title marker" id="h-note-3" aria-level="3"><span>Note</span></div><p class="">JavaScript applications <em class="rfc2119">SHOULD</em> use this status code to terminate playback with a network error. For example, if a network error occurs while fetching media data.</p></div>
</td></tr><tr><td><dfn data-export="" data-dfn-type="enum-value" id="dom-endofstreamerror-decode" data-idl="enum-value" data-title="decode" data-dfn-for="EndOfStreamError"><code id="idl-def-EndOfStreamError.decode">decode</code></dfn></td><td>
<p>Terminates playback and signals that a decoding error has occured.</p>
<div class="note" role="note" id="issue-container-generatedID-4"><div role="heading" class="note-title marker" id="h-note-4" aria-level="3"><span>Note</span></div><p class="">JavaScript applications <em class="rfc2119">SHOULD</em> use this status code to terminate playback with a decode error. For example, if a parsing error occurs while processing out-of-band media data.</p></div>
</td></tr></tbody></table></div>
<pre class="idl def" id="webidl-709154601"><span class="idlHeader"><a class="self-link" href="#webidl-709154601">WebIDL</a></span><span data-idl="" class="idlInterface" id="idl-def-mediasource" data-title="MediaSource">[<span class="extAttr"><a data-type="extended-attribute" href="https://heycam.github.io/webidl/#Exposed">Exposed</a>=<a data-type="interface" href="https://html.spec.whatwg.org/multipage/window-object.html#window">Window</a></span>]
interface <a class="internalDFN idlID" data-link-type="interface" href="#dom-mediasource" id="ref-for-dom-mediasource-9"><code>MediaSource</code></a> : <span class="idlSuperclass"><a data-type="interface" href="https://dom.spec.whatwg.org/#eventtarget">EventTarget</a></span> {<span data-idl="" class="idlConstructor" id="idl-def-mediasource-constructor" data-title="constructor" data-dfn-for="MediaSource">
<dfn data-export="" data-dfn-type="constructor" id="dom-mediasource-constructor" data-idl="constructor" data-title="constructor" data-dfn-for="MediaSource" data-lt="constructor()" data-local-lt="MediaSource.constructor|MediaSource.constructor()|constructor"><code>constructor</code></dfn>();</span><span data-idl="" class="idlAttribute" id="idl-def-mediasource-sourcebuffers" data-title="sourceBuffers" data-dfn-for="MediaSource">
readonly attribute<span class="idlType"> <a href="#dom-sourcebufferlist" class="internalDFN" data-link-type="idl" id="ref-for-dom-sourcebufferlist-1"><code>SourceBufferList</code></a></span> <a class="internalDFN idlName" data-link-type="attribute" href="#dom-mediasource-sourcebuffers" id="ref-for-dom-mediasource-sourcebuffers-1"><code>sourceBuffers</code></a>;</span><span data-idl="" class="idlAttribute" id="idl-def-mediasource-activesourcebuffers" data-title="activeSourceBuffers" data-dfn-for="MediaSource">
readonly attribute<span class="idlType"> <a href="#dom-sourcebufferlist" class="internalDFN" data-link-type="idl" id="ref-for-dom-sourcebufferlist-2"><code>SourceBufferList</code></a></span> <a class="internalDFN idlName" data-link-type="attribute" href="#dom-mediasource-activesourcebuffers" id="ref-for-dom-mediasource-activesourcebuffers-1"><code>activeSourceBuffers</code></a>;</span><span data-idl="" class="idlAttribute" id="idl-def-mediasource-readystate" data-title="readyState" data-dfn-for="MediaSource">
readonly attribute<span class="idlType"> <a href="#dom-readystate" class="internalDFN" data-link-type="idl" id="ref-for-dom-readystate-1"><code>ReadyState</code></a></span> <a class="internalDFN idlName" data-link-type="attribute" href="#dom-mediasource-readystate" id="ref-for-dom-mediasource-readystate-2"><code>readyState</code></a>;</span><span data-idl="" class="idlAttribute" id="idl-def-mediasource-duration" data-title="duration" data-dfn-for="MediaSource">
attribute<span class="idlType"> <a data-type="interface" href="https://heycam.github.io/webidl/#idl-unrestricted-double">unrestricted double</a></span> <a class="internalDFN idlName" data-link-type="attribute" href="#dom-mediasource-duration" id="ref-for-dom-mediasource-duration-1"><code>duration</code></a>;</span><span data-idl="" class="idlAttribute" id="idl-def-mediasource-onsourceopen" data-title="onsourceopen" data-dfn-for="MediaSource">
attribute<span class="idlType"> <a data-type="typedef" href="https://html.spec.whatwg.org/multipage/webappapis.html#eventhandler">EventHandler</a></span> <a class="internalDFN idlName" data-link-type="attribute" href="#dom-mediasource-onsourceopen" id="ref-for-dom-mediasource-onsourceopen-1"><code>onsourceopen</code></a>;</span><span data-idl="" class="idlAttribute" id="idl-def-mediasource-onsourceended" data-title="onsourceended" data-dfn-for="MediaSource">
attribute<span class="idlType"> <a data-type="typedef" href="https://html.spec.whatwg.org/multipage/webappapis.html#eventhandler">EventHandler</a></span> <a class="internalDFN idlName" data-link-type="attribute" href="#dom-mediasource-onsourceended" id="ref-for-dom-mediasource-onsourceended-1"><code>onsourceended</code></a>;</span><span data-idl="" class="idlAttribute" id="idl-def-mediasource-onsourceclose" data-title="onsourceclose" data-dfn-for="MediaSource">
attribute<span class="idlType"> <a data-type="typedef" href="https://html.spec.whatwg.org/multipage/webappapis.html#eventhandler">EventHandler</a></span> <a class="internalDFN idlName" data-link-type="attribute" href="#dom-mediasource-onsourceclose" id="ref-for-dom-mediasource-onsourceclose-1"><code>onsourceclose</code></a>;</span><span data-idl="" class="idlMethod" id="idl-def-mediasource-addsourcebuffer-type" data-title="addSourceBuffer" data-dfn-for="MediaSource"><span class="idlType">
<a href="#dom-sourcebuffer" class="internalDFN" data-link-type="idl" id="ref-for-dom-sourcebuffer-13"><code>SourceBuffer</code></a></span> <a class="internalDFN idlName" data-link-type="method" href="#dom-mediasource-addsourcebuffer" id="ref-for-dom-mediasource-addsourcebuffer-1"><code>addSourceBuffer</code></a> (<span class="idlType"><a data-type="interface" href="https://heycam.github.io/webidl/#idl-DOMString">DOMString</a></span> <span class="idlParamName">type</span>);</span><span data-idl="" class="idlMethod" id="idl-def-mediasource-removesourcebuffer-sourcebuffer" data-title="removeSourceBuffer" data-dfn-for="MediaSource"><span class="idlType">
<a data-type="interface" href="https://heycam.github.io/webidl/#idl-undefined">undefined</a></span> <a class="internalDFN idlName" data-link-type="method" href="#dom-mediasource-removesourcebuffer" id="ref-for-dom-mediasource-removesourcebuffer-1"><code>removeSourceBuffer</code></a> (<span class="idlType"><a href="#dom-sourcebuffer" class="internalDFN" data-link-type="idl" id="ref-for-dom-sourcebuffer-14"><code>SourceBuffer</code></a></span> <span class="idlParamName">sourceBuffer</span>);</span><span data-idl="" class="idlMethod" id="idl-def-mediasource-endofstream-error" data-title="endOfStream" data-dfn-for="MediaSource"><span class="idlType">
<a data-type="interface" href="https://heycam.github.io/webidl/#idl-undefined">undefined</a></span> <a class="internalDFN idlName" data-link-type="method" href="#dom-mediasource-endofstream" id="ref-for-dom-mediasource-endofstream-1"><code>endOfStream</code></a> (optional<span class="idlType"> <a href="#dom-endofstreamerror" class="internalDFN" data-link-type="idl" id="ref-for-dom-endofstreamerror-1"><code>EndOfStreamError</code></a></span> <span class="idlParamName">error</span>);</span><span data-idl="" class="idlMethod" id="idl-def-mediasource-setliveseekablerange-start-end" data-title="setLiveSeekableRange" data-dfn-for="MediaSource"><span class="idlType">
<a data-type="interface" href="https://heycam.github.io/webidl/#idl-undefined">undefined</a></span> <a class="internalDFN idlName" data-link-type="method" href="#dom-mediasource-setliveseekablerange" id="ref-for-dom-mediasource-setliveseekablerange-1"><code>setLiveSeekableRange</code></a> (<span class="idlType"><a data-type="interface" href="https://heycam.github.io/webidl/#idl-double">double</a></span> <span class="idlParamName">start</span>,<span class="idlType"> <a data-type="interface" href="https://heycam.github.io/webidl/#idl-double">double</a></span> <span class="idlParamName">end</span>);</span><span data-idl="" class="idlMethod" id="idl-def-mediasource-clearliveseekablerange" data-title="clearLiveSeekableRange" data-dfn-for="MediaSource"><span class="idlType">
<a data-type="interface" href="https://heycam.github.io/webidl/#idl-undefined">undefined</a></span> <a class="internalDFN idlName" data-link-type="method" href="#dom-mediasource-clearliveseekablerange" id="ref-for-dom-mediasource-clearliveseekablerange-1"><code>clearLiveSeekableRange</code></a> ();</span><span data-idl="" class="idlMethod" id="idl-def-mediasource-istypesupported-type" data-title="isTypeSupported" data-dfn-for="MediaSource">
static<span class="idlType"> <a data-type="interface" href="https://heycam.github.io/webidl/#idl-boolean">boolean</a></span> <a class="internalDFN idlName" data-link-type="method" href="#dom-mediasource-istypesupported" id="ref-for-dom-mediasource-istypesupported-1"><code>isTypeSupported</code></a> (<span class="idlType"><a data-type="interface" href="https://heycam.github.io/webidl/#idl-DOMString">DOMString</a></span> <span class="idlParamName">type</span>);</span>
};</span></pre>
<section id="attributes">
<h3 id="x2-1-attributes"><bdi class="secno">2.1 </bdi>Attributes<a class="self-link" aria-label="§" href="#attributes"></a></h3>
<dl class="attributes" data-dfn-for="MediaSource"><dt><dfn data-export="" data-dfn-type="attribute" id="dom-mediasource-sourcebuffers" data-idl="attribute" data-title="sourceBuffers" data-dfn-for="MediaSource" data-type="SourceBufferList" data-lt="sourceBuffers" data-local-lt="MediaSource.sourceBuffers"><code>sourceBuffers</code></dfn> of type <span class="idlAttrType"><a href="#dom-sourcebufferlist" class="internalDFN" data-link-type="idl" id="ref-for-dom-sourcebufferlist-3"><code>SourceBufferList</code></a></span>, readonly </dt><dd>
Contains the list of <a href="#dom-sourcebuffer" class="internalDFN" data-link-type="idl" id="ref-for-dom-sourcebuffer-15"><code>SourceBuffer</code></a> objects associated with this <a href="#dom-mediasource" class="internalDFN" data-link-type="idl" id="ref-for-dom-mediasource-10"><code>MediaSource</code></a>. When <a data-link-type="idl" href="#dom-mediasource-readystate" class="internalDFN" id="ref-for-dom-mediasource-readystate-3"><code><code>readyState</code></code></a> equals <code><a href="#dom-readystate-closed">"closed"</a></code> this list will be empty. Once <a data-link-type="idl" href="#dom-mediasource-readystate" class="internalDFN" id="ref-for-dom-mediasource-readystate-4"><code><code>readyState</code></code></a> transitions to <code><a href="#dom-readystate-open">"open"</a></code> SourceBuffer objects can be added to this list by using <code><a href="#dom-mediasource-addsourcebuffer">addSourceBuffer()</a></code>.
</dd><dt><dfn data-export="" data-dfn-type="attribute" id="dom-mediasource-activesourcebuffers" data-idl="attribute" data-title="activeSourceBuffers" data-dfn-for="MediaSource" data-type="SourceBufferList" data-lt="activeSourceBuffers" data-local-lt="MediaSource.activeSourceBuffers"><code>activeSourceBuffers</code></dfn> of type <span class="idlAttrType"><a href="#dom-sourcebufferlist" class="internalDFN" data-link-type="idl" id="ref-for-dom-sourcebufferlist-4"><code>SourceBufferList</code></a></span>, readonly </dt><dd>
<p>Contains the subset of <code><a href="#dom-mediasource-sourcebuffers">sourceBuffers</a></code> that are providing the
<a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-videotrack-selected">selected video track</a>, the
<a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-audiotrack-enabled">enabled audio track(s)</a>, and the
<code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-texttrackmode-showing">"showing"</a></code> or <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-texttrackmode-hidden">"hidden"</a></code> text track(s).
</p>
<p><a href="#dom-sourcebuffer" class="internalDFN" data-link-type="idl" id="ref-for-dom-sourcebuffer-16"><code>SourceBuffer</code></a> objects in this list <em class="rfc2119">MUST</em> appear in the same order as they appear in
the <code><a href="#dom-mediasource-sourcebuffers">sourceBuffers</a></code> attribute; e.g., if only sourceBuffers[0] and
sourceBuffers[3] are in <code><a href="#dom-mediasource-activesourcebuffers">activeSourceBuffers</a></code>, then activeSourceBuffers[0] <em class="rfc2119">MUST</em>
equal sourceBuffers[0] and activeSourceBuffers[1] <em class="rfc2119">MUST</em> equal sourceBuffers[3].
</p>
<div class="note" role="note" id="issue-container-generatedID-5"><div role="heading" class="note-title marker" id="h-note-5" aria-level="4"><span>Note</span></div><p class="">The <a href="#active-source-buffer-changes">Changes to selected/enabled track state</a> section describes how this attribute gets
updated.</p></div>
</dd><dt><dfn data-export="" data-dfn-type="attribute" id="dom-mediasource-readystate" data-idl="attribute" data-title="readyState" data-dfn-for="MediaSource" data-type="ReadyState" data-lt="readyState" data-local-lt="MediaSource.readyState"><code>readyState</code></dfn> of type <a data-link-type="idl" href="#dom-readystate" class="internalDFN" id="ref-for-dom-readystate-2"><code><code>ReadyState</code></code></a>, readonly </dt><dd>
<p>Indicates the current state of the <a href="#dom-mediasource" class="internalDFN" data-link-type="idl" id="ref-for-dom-mediasource-11"><code>MediaSource</code></a> object. When the <a href="#dom-mediasource" class="internalDFN" data-link-type="idl" id="ref-for-dom-mediasource-12"><code>MediaSource</code></a> is created <a data-link-type="idl" href="#dom-mediasource-readystate" class="internalDFN" id="ref-for-dom-mediasource-readystate-5"><code><code>readyState</code></code></a> <em class="rfc2119">MUST</em> be set to <code><a href="#dom-readystate-closed">"closed"</a></code>.
</p></dd><dt><dfn data-export="" data-dfn-type="attribute" id="dom-mediasource-duration" data-idl="attribute" data-title="duration" data-dfn-for="MediaSource" data-type="unrestricted double" data-lt="duration" data-local-lt="MediaSource.duration"><code>duration</code></dfn> of type <span class="idlAttrType"><code><a href="https://www.w3.org/TR/WebIDL-1/#idl-unrestricted-double">unrestricted double</a></code></span></dt><dd>
<p>Allows the web application to set the presentation duration. The duration is initially set to NaN when the <a href="#dom-mediasource" class="internalDFN" data-link-type="idl" id="ref-for-dom-mediasource-13"><code>MediaSource</code></a> object is created.</p>
<p>On getting, run the following steps:</p>
<ol>
<li>If the <a data-link-type="idl" href="#dom-mediasource-readystate" class="internalDFN" id="ref-for-dom-mediasource-readystate-6"><code><code>readyState</code></code></a> attribute is <code><a href="#dom-readystate-closed">"closed"</a></code> then return NaN and abort these steps.</li>
<li>Return the current value of the attribute.</li>
</ol>
<p>On setting, run the following steps:</p>
<ol>
<li>If the value being set is negative or NaN then throw a <code>TypeError</code> exception and abort these steps.</li>
<li>If the <a data-link-type="idl" href="#dom-mediasource-readystate" class="internalDFN" id="ref-for-dom-mediasource-readystate-7"><code><code>readyState</code></code></a> attribute is not <code><a href="#dom-readystate-open">"open"</a></code> then throw an <code><a href="https://www.w3.org/TR/WebIDL-1/#invalidstateerror">InvalidStateError</a></code> exception and abort these steps.</li>
<li>If the <code><a href="#dom-sourcebuffer-updating">updating</a></code> attribute equals true on any <a href="#dom-sourcebuffer" class="internalDFN" data-link-type="idl" id="ref-for-dom-sourcebuffer-17"><code>SourceBuffer</code></a> in <code><a href="#dom-mediasource-sourcebuffers">sourceBuffers</a></code>, then throw an <code><a href="https://www.w3.org/TR/WebIDL-1/#invalidstateerror">InvalidStateError</a></code> exception and abort these steps.</li>
<li>Run the <a href="#duration-change-algorithm">duration change algorithm</a> with <var>new duration</var> set to the value being assigned to this attribute.
<div class="note" role="note" id="issue-container-generatedID-6"><div role="heading" class="note-title marker" id="h-note-6" aria-level="4"><span>Note</span></div><p class="">The <a href="#duration-change-algorithm">duration change algorithm</a> will adjust <var>new duration</var> higher if there is any currently buffered coded frame with a higher end time.</p></div>
<div class="note" role="note" id="issue-container-generatedID-7"><div role="heading" class="note-title marker" id="h-note-7" aria-level="4"><span>Note</span></div><p class=""><code><a href="#dom-sourcebuffer-appendbuffer">appendBuffer()</a></code> and <code><a href="#dom-mediasource-endofstream">endOfStream()</a></code> can update the duration under certain circumstances.</p></div>
</li>
</ol>
</dd><dt><dfn data-export="" data-dfn-type="attribute" id="dom-mediasource-onsourceopen" data-idl="attribute" data-title="onsourceopen" data-dfn-for="MediaSource" data-type="EventHandler" data-lt="onsourceopen" data-local-lt="MediaSource.onsourceopen"><code>onsourceopen</code></dfn> of type <span class="idlAttrType"><code><a href="https://www.w3.org/TR/html51/webappapis.html#typedefdef-eventhandlernonnull-eventhandler">EventHandler</a></code></span></dt><dd>
<p>The event handler for the <code><a href="#dom-evt-sourceopen">sourceopen</a></code> event.</p>
</dd><dt><dfn data-export="" data-dfn-type="attribute" id="dom-mediasource-onsourceended" data-idl="attribute" data-title="onsourceended" data-dfn-for="MediaSource" data-type="EventHandler" data-lt="onsourceended" data-local-lt="MediaSource.onsourceended"><code>onsourceended</code></dfn> of type <span class="idlAttrType"><code><a href="https://www.w3.org/TR/html51/webappapis.html#typedefdef-eventhandlernonnull-eventhandler">EventHandler</a></code></span></dt><dd>
<p>The event handler for the <code><a href="#dom-evt-sourceended">sourceended</a></code> event.</p>
</dd><dt><dfn data-export="" data-dfn-type="attribute" id="dom-mediasource-onsourceclose" data-idl="attribute" data-title="onsourceclose" data-dfn-for="MediaSource" data-type="EventHandler" data-lt="onsourceclose" data-local-lt="MediaSource.onsourceclose"><code>onsourceclose</code></dfn> of type <span class="idlAttrType"><code><a href="https://www.w3.org/TR/html51/webappapis.html#typedefdef-eventhandlernonnull-eventhandler">EventHandler</a></code></span></dt><dd>
<p>The event handler for the <code><a href="#dom-evt-sourceclose">sourceclose</a></code> event.</p>
</dd></dl></section><section id="methods"><h3 id="x2-2-methods"><bdi class="secno">2.2 </bdi>Methods<a class="self-link" aria-label="§" href="#methods"></a></h3><dl class="methods" data-dfn-for="MediaSource" data-link-for="MediaSource"><dt><dfn data-export="" data-dfn-type="method" id="dom-mediasource-addsourcebuffer" data-idl="operation" data-title="addSourceBuffer" data-dfn-for="MediaSource" data-type="SourceBuffer" data-lt="addSourceBuffer()|addSourceBuffer(type)" data-local-lt="MediaSource.addSourceBuffer|MediaSource.addSourceBuffer()|addSourceBuffer"><code>addSourceBuffer</code></dfn></dt><dd>
<p>Adds a new <a href="#dom-sourcebuffer" class="internalDFN" data-link-type="idl" id="ref-for-dom-sourcebuffer-18"><code>SourceBuffer</code></a> to <code><a href="#dom-mediasource-sourcebuffers">sourceBuffers</a></code>.</p>
<table class="parameters"><tbody><tr><th>Parameter</th><th>Type</th><th>Nullable</th><th>Optional</th><th>Description</th></tr><tr><td class="prmName">type</td><td class="prmType"><code><a href="https://www.w3.org/TR/WebIDL-1/#idl-DOMString">DOMString</a></code></td><td class="prmNullFalse"><span role="img" aria-label="False">✘</span></td><td class="prmOptFalse"><span role="img" aria-label="False">✘</span></td><td class="prmDesc"></td></tr></tbody></table><div><em>Return type: </em><a href="#dom-sourcebuffer" class="internalDFN" data-link-type="idl" id="ref-for-dom-sourcebuffer-21"><code>SourceBuffer</code></a></div><p>When this method is invoked, the user agent must run the following steps:</p><ol class="method-algorithm">
<li>If <var>type</var> is an empty string then throw a <code>TypeError</code> exception and abort these steps.</li>
<li>If <var>type</var> contains a MIME type that is not supported or contains a MIME type that is not supported with the types specified for the other <a href="#dom-sourcebuffer" class="internalDFN" data-link-type="idl" id="ref-for-dom-sourcebuffer-19"><code>SourceBuffer</code></a> objects in <code><a href="#dom-mediasource-sourcebuffers">sourceBuffers</a></code>, then throw a <code><a href="https://www.w3.org/TR/WebIDL-1/#notsupportederror">NotSupportedError</a></code> exception and abort these steps.</li>
<li>If the user agent can't handle any more SourceBuffer objects or if creating a SourceBuffer
based on <var>type</var> would result in an unsupported <a href="#sourcebuffer-configuration">SourceBuffer configuration</a>,
then throw a <code><a href="https://www.w3.org/TR/WebIDL-1/#quotaexceedederror">QuotaExceededError</a></code> exception and abort these steps.
<div class="note" role="note" id="issue-container-generatedID-8"><div role="heading" class="note-title marker" id="h-note-8" aria-level="4"><span>Note</span></div><p class="">For example, a user agent <em class="rfc2119">MAY</em> throw a <code><a href="https://www.w3.org/TR/WebIDL-1/#quotaexceedederror">QuotaExceededError</a></code> exception if the media element has reached the
<code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-have_metadata">HAVE_METADATA</a></code> readyState. This can occur if the user agent's media engine does not support adding more tracks during
playback.
</p></div>
</li>
<li>If the <a data-link-type="idl" href="#dom-mediasource-readystate" class="internalDFN" id="ref-for-dom-mediasource-readystate-8"><code><code>readyState</code></code></a> attribute is not in the <code><a href="#dom-readystate-open">"open"</a></code> state then throw an <code><a href="https://www.w3.org/TR/WebIDL-1/#invalidstateerror">InvalidStateError</a></code> exception and abort these steps.</li>
<li>Create a new <a href="#dom-sourcebuffer" class="internalDFN" data-link-type="idl" id="ref-for-dom-sourcebuffer-20"><code>SourceBuffer</code></a> object and associated resources.</li>
<li>Set the <var><a href="#sourcebuffer-generate-timestamps-flag">generate timestamps flag</a></var> on the new object to the value in the
"Generate Timestamps Flag" column of the byte stream format registry [<cite><a class="bibref" data-link-type="biblio" href="#bib-mse-registry" title="Media Source Extensions™ Byte Stream Format Registry">MSE-REGISTRY</a></cite>] entry
that is associated with <var>type</var>.
</li><li>
<dl class="switch">
<dt>If the <var><a href="#sourcebuffer-generate-timestamps-flag">generate timestamps flag</a></var> equals true:</dt>
<dd>
Set the <code><a href="#dom-sourcebuffer-mode">mode</a></code> attribute on the new object to
<code><a href="#dom-appendmode-sequence">"sequence"</a></code>.
</dd>
<dt>Otherwise:</dt>
<dd>
Set the <code><a href="#dom-sourcebuffer-mode">mode</a></code> attribute on the new object to
<code><a href="#dom-appendmode-segments">"segments"</a></code>.
</dd>
</dl>
</li>
<li>Add the new object to <code><a href="#dom-mediasource-sourcebuffers">sourceBuffers</a></code> and <a href="https://www.w3.org/TR/html51/webappapis.html#queuing">queue a task</a> to <a href="https://www.w3.org/TR/html51/infrastructure.html#fire">fire a simple event</a> named <code><a href="#dom-evt-addsourcebuffer">addsourcebuffer</a></code> at <code><a href="#dom-mediasource-sourcebuffers">sourceBuffers</a></code>.</li>
<li>Return the new object.</li>
</ol></dd><dt><dfn data-export="" data-dfn-type="method" id="dom-mediasource-removesourcebuffer" data-idl="operation" data-title="removeSourceBuffer" data-dfn-for="MediaSource" data-type="undefined" data-lt="removeSourceBuffer()|removeSourceBuffer(sourceBuffer)" data-local-lt="MediaSource.removeSourceBuffer|MediaSource.removeSourceBuffer()|removeSourceBuffer"><code>removeSourceBuffer</code></dfn></dt><dd>
<p>Removes a <a href="#dom-sourcebuffer" class="internalDFN" data-link-type="idl" id="ref-for-dom-sourcebuffer-22"><code>SourceBuffer</code></a> from <code><a href="#dom-mediasource-sourcebuffers">sourceBuffers</a></code>.</p>
<table class="parameters"><tbody><tr><th>Parameter</th><th>Type</th><th>Nullable</th><th>Optional</th><th>Description</th></tr><tr><td class="prmName">sourceBuffer</td><td class="prmType"><code>SourceBuffer</code></td><td class="prmNullFalse"><span role="img" aria-label="False">✘</span></td><td class="prmOptFalse"><span role="img" aria-label="False">✘</span></td><td class="prmDesc"></td></tr></tbody></table><div><em>Return type: </em><code><a href="https://www.w3.org/TR/WebIDL-1/#idl-void" class="idlType">void</a></code></div><p>When this method is invoked, the user agent must run the following steps:</p><ol class="method-algorithm">
<li>If <var>sourceBuffer</var> specifies an object that is not in <code><a href="#dom-mediasource-sourcebuffers">sourceBuffers</a></code> then throw a <code><a href="https://www.w3.org/TR/WebIDL-1/#notfounderror">NotFoundError</a></code> exception and abort these steps.</li>
<li>If the <var>sourceBuffer</var>.<code><a href="#dom-sourcebuffer-updating">updating</a></code> attribute equals true, then run the following steps:
<ol>
<li>Abort the <a href="#sourcebuffer-buffer-append">buffer append</a> algorithm if it is running.</li>
<li>Set the <var>sourceBuffer</var>.<code><a href="#dom-sourcebuffer-updating">updating</a></code> attribute to false.</li>
<li><a href="https://www.w3.org/TR/html51/webappapis.html#queuing">Queue a task</a> to <a href="https://www.w3.org/TR/html51/infrastructure.html#fire">fire a simple event</a> named <code><a href="#dom-evt-abort">abort</a></code> at <var>sourceBuffer</var>.</li>
<li><a href="https://www.w3.org/TR/html51/webappapis.html#queuing">Queue a task</a> to <a href="https://www.w3.org/TR/html51/infrastructure.html#fire">fire a simple event</a> named <code><a href="#dom-evt-updateend">updateend</a></code> at <var>sourceBuffer</var>.</li>
</ol>
</li>
<li>Let <var>SourceBuffer audioTracks list</var> equal the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#audiotracklist-audiotracklist">AudioTrackList</a></code> object returned by <var>sourceBuffer</var>.<code><a href="#dom-sourcebuffer-audiotracks">audioTracks</a></code>.</li>
<li>If the <var>SourceBuffer audioTracks list</var> is not empty, then run the following steps:
<ol>
<li>Let <var>HTMLMediaElement audioTracks list</var> equal the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#audiotracklist-audiotracklist">AudioTrackList</a></code> object returned by the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-audiotracks">audioTracks</a></code> attribute on the HTMLMediaElement.</li>
<li>For each <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#audiotrack-audiotrack">AudioTrack</a></code> object in the <var>SourceBuffer audioTracks list</var>, run the following steps:
<ol>
<li>Set the <code><a href="#dom-audiotrack-sourcebuffer">sourceBuffer</a></code> attribute on the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#audiotrack-audiotrack">AudioTrack</a></code> object to null.</li>
<li>Remove the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#audiotrack-audiotrack">AudioTrack</a></code> object from the <var>HTMLMediaElement audioTracks list</var>.
<div class="note" role="note" id="issue-container-generatedID-9"><div role="heading" class="note-title marker" id="h-note-9" aria-level="4"><span>Note</span></div><p class="">
This should trigger <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#audiotracklist-audiotracklist">AudioTrackList</a></code> [<cite><a class="bibref" data-link-type="biblio" href="#bib-html" title="HTML Standard">HTML</a></cite>] logic to <a href="https://www.w3.org/TR/html51/webappapis.html#queuing">queue a task</a> to fire a <a href="https://www.w3.org/TR/html51/infrastructure.html#trusted">trusted event</a> named <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-mediatracklist-onremovetrack">removetrack</a></code>, that does not bubble and is not cancelable, and that uses the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#trackevent-trackevent">TrackEvent</a></code> interface, with the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-trackevent-track">track</a></code> attribute initialized to the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#audiotrack-audiotrack">AudioTrack</a></code> object, at the <var>HTMLMediaElement audioTracks list</var>.
If the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-audiotrack-enabled">enabled</a></code> attribute on the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#audiotrack-audiotrack">AudioTrack</a></code> object was true at the beginning of this removal step, then this should also trigger <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#audiotracklist-audiotracklist">AudioTrackList</a></code> [<cite><a class="bibref" data-link-type="biblio" href="#bib-html" title="HTML Standard">HTML</a></cite>] logic to <a href="https://www.w3.org/TR/html51/webappapis.html#queuing">queue a task</a> to <a href="https://www.w3.org/TR/html51/infrastructure.html#fire">fire a simple event</a> named <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-mediatracklist-onchange">change</a></code> at the <var>HTMLMediaElement audioTracks list</var>
</p></div>
</li>
<li>Remove the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#audiotrack-audiotrack">AudioTrack</a></code> object from the <var>SourceBuffer audioTracks list</var>.
<div class="note" role="note" id="issue-container-generatedID-10"><div role="heading" class="note-title marker" id="h-note-10" aria-level="4"><span>Note</span></div><p class="">
This should trigger <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#audiotracklist-audiotracklist">AudioTrackList</a></code> [<cite><a class="bibref" data-link-type="biblio" href="#bib-html" title="HTML Standard">HTML</a></cite>] logic to <a href="https://www.w3.org/TR/html51/webappapis.html#queuing">queue a task</a> to fire a <a href="https://www.w3.org/TR/html51/infrastructure.html#trusted">trusted event</a> named <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-mediatracklist-onremovetrack">removetrack</a></code>, that does not bubble and is not cancelable, and that uses the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#trackevent-trackevent">TrackEvent</a></code> interface, with the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-trackevent-track">track</a></code> attribute initialized to the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#audiotrack-audiotrack">AudioTrack</a></code> object, at the <var>SourceBuffer audioTracks list</var>.
If the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-audiotrack-enabled">enabled</a></code> attribute on the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#audiotrack-audiotrack">AudioTrack</a></code> object was true at the beginning of this removal step, then this should also trigger <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#audiotracklist-audiotracklist">AudioTrackList</a></code> [<cite><a class="bibref" data-link-type="biblio" href="#bib-html" title="HTML Standard">HTML</a></cite>] logic to <a href="https://www.w3.org/TR/html51/webappapis.html#queuing">queue a task</a> to <a href="https://www.w3.org/TR/html51/infrastructure.html#fire">fire a simple event</a> named <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-mediatracklist-onchange">change</a></code> at the <var>SourceBuffer audioTracks list</var>
</p></div>
</li>
</ol>
</li>
</ol>
</li>
<li>Let <var>SourceBuffer videoTracks list</var> equal the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#videotracklist-videotracklist">VideoTrackList</a></code> object returned by <var>sourceBuffer</var>.<code><a href="#dom-sourcebuffer-videotracks">videoTracks</a></code>.</li>
<li>If the <var>SourceBuffer videoTracks list</var> is not empty, then run the following steps:
<ol>
<li>Let <var>HTMLMediaElement videoTracks list</var> equal the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#videotracklist-videotracklist">VideoTrackList</a></code> object returned by the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-videotracks">videoTracks</a></code> attribute on the HTMLMediaElement.</li>
<li>For each <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#videotrack-videotrack">VideoTrack</a></code> object in the <var>SourceBuffer videoTracks list</var>, run the following steps:
<ol>
<li>Set the <code><a href="#dom-videotrack-sourcebuffer">sourceBuffer</a></code> attribute on the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#videotrack-videotrack">VideoTrack</a></code> object to null.</li>
<li>Remove the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#videotrack-videotrack">VideoTrack</a></code> object from the <var>HTMLMediaElement videoTracks list</var>.
<div class="note" role="note" id="issue-container-generatedID-11"><div role="heading" class="note-title marker" id="h-note-11" aria-level="4"><span>Note</span></div><p class="">
This should trigger <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#videotracklist-videotracklist">VideoTrackList</a></code> [<cite><a class="bibref" data-link-type="biblio" href="#bib-html" title="HTML Standard">HTML</a></cite>] logic to <a href="https://www.w3.org/TR/html51/webappapis.html#queuing">queue a task</a> to fire a <a href="https://www.w3.org/TR/html51/infrastructure.html#trusted">trusted event</a> named <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-mediatracklist-onremovetrack">removetrack</a></code>, that does not bubble and is not cancelable, and that uses the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#trackevent-trackevent">TrackEvent</a></code> interface, with the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-trackevent-track">track</a></code> attribute initialized to the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#videotrack-videotrack">VideoTrack</a></code> object, at the <var>HTMLMediaElement videoTracks list</var>.
If the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-videotrack-selected">selected</a></code> attribute on the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#videotrack-videotrack">VideoTrack</a></code> object was true at the beginning of this removal step, then this should also trigger <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#videotracklist-videotracklist">VideoTrackList</a></code> [<cite><a class="bibref" data-link-type="biblio" href="#bib-html" title="HTML Standard">HTML</a></cite>] logic to <a href="https://www.w3.org/TR/html51/webappapis.html#queuing">queue a task</a> to <a href="https://www.w3.org/TR/html51/infrastructure.html#fire">fire a simple event</a> named <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-mediatracklist-onchange">change</a></code> at the <var>HTMLMediaElement videoTracks list</var>
</p></div>
</li>
<li>Remove the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#videotrack-videotrack">VideoTrack</a></code> object from the <var>SourceBuffer videoTracks list</var>.
<div class="note" role="note" id="issue-container-generatedID-12"><div role="heading" class="note-title marker" id="h-note-12" aria-level="4"><span>Note</span></div><p class="">
This should trigger <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#videotracklist-videotracklist">VideoTrackList</a></code> [<cite><a class="bibref" data-link-type="biblio" href="#bib-html" title="HTML Standard">HTML</a></cite>] logic to <a href="https://www.w3.org/TR/html51/webappapis.html#queuing">queue a task</a> to fire a <a href="https://www.w3.org/TR/html51/infrastructure.html#trusted">trusted event</a> named <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-mediatracklist-onremovetrack">removetrack</a></code>, that does not bubble and is not cancelable, and that uses the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#trackevent-trackevent">TrackEvent</a></code> interface, with the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-trackevent-track">track</a></code> attribute initialized to the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#videotrack-videotrack">VideoTrack</a></code> object, at the <var>SourceBuffer videoTracks list</var>.
If the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-videotrack-selected">selected</a></code> attribute on the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#videotrack-videotrack">VideoTrack</a></code> object was true at the beginning of this removal step, then this should also trigger <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#videotracklist-videotracklist">VideoTrackList</a></code> [<cite><a class="bibref" data-link-type="biblio" href="#bib-html" title="HTML Standard">HTML</a></cite>] logic to <a href="https://www.w3.org/TR/html51/webappapis.html#queuing">queue a task</a> to <a href="https://www.w3.org/TR/html51/infrastructure.html#fire">fire a simple event</a> named <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-mediatracklist-onchange">change</a></code> at the <var>SourceBuffer videoTracks list</var>
</p></div>
</li>
</ol>
</li>
</ol>
</li>
<li>Let <var>SourceBuffer textTracks list</var> equal the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#texttracklist-texttracklist">TextTrackList</a></code> object returned by <var>sourceBuffer</var>.<code><a href="#dom-sourcebuffer-texttracks">textTracks</a></code>.</li>
<li>If the <var>SourceBuffer textTracks list</var> is not empty, then run the following steps:
<ol>
<li>Let <var>HTMLMediaElement textTracks list</var> equal the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#texttracklist-texttracklist">TextTrackList</a></code> object returned by the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-texttracks">textTracks</a></code> attribute on the HTMLMediaElement.</li>
<li>For each <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#texttrack-texttrack">TextTrack</a></code> object in the <var>SourceBuffer textTracks list</var>, run the following steps:
<ol>
<li>Set the <code><a href="#dom-texttrack-sourcebuffer">sourceBuffer</a></code> attribute on the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#texttrack-texttrack">TextTrack</a></code> object to null.</li>
<li>Remove the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#texttrack-texttrack">TextTrack</a></code> object from the <var>HTMLMediaElement textTracks list</var>.
<div class="note" role="note" id="issue-container-generatedID-13"><div role="heading" class="note-title marker" id="h-note-13" aria-level="4"><span>Note</span></div><p class="">
This should trigger <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#texttracklist-texttracklist">TextTrackList</a></code> [<cite><a class="bibref" data-link-type="biblio" href="#bib-html" title="HTML Standard">HTML</a></cite>] logic to <a href="https://www.w3.org/TR/html51/webappapis.html#queuing">queue a task</a> to fire a <a href="https://www.w3.org/TR/html51/infrastructure.html#trusted">trusted event</a> named <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-texttracklist-onremovetrack">removetrack</a></code>, that does not bubble and is not cancelable, and that uses the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#trackevent-trackevent">TrackEvent</a></code> interface, with the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-trackevent-track">track</a></code> attribute initialized to the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#texttrack-texttrack">TextTrack</a></code> object, at the <var>HTMLMediaElement textTracks list</var>.
If the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-texttrack-mode">mode</a></code> attribute on the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#texttrack-texttrack">TextTrack</a></code> object was <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-texttrackmode-showing">"showing"</a></code> or <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-texttrackmode-hidden">"hidden"</a></code> at the beginning of this removal step, then this should also trigger <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#texttracklist-texttracklist">TextTrackList</a></code> [<cite><a class="bibref" data-link-type="biblio" href="#bib-html" title="HTML Standard">HTML</a></cite>] logic to <a href="https://www.w3.org/TR/html51/webappapis.html#queuing">queue a task</a> to <a href="https://www.w3.org/TR/html51/infrastructure.html#fire">fire a simple event</a> named <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-texttracklist-onchange">change</a></code> at the <var>HTMLMediaElement textTracks list</var>.
</p></div>
</li>
<li>Remove the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#texttrack-texttrack">TextTrack</a></code> object from the <var>SourceBuffer textTracks list</var>.
<div class="note" role="note" id="issue-container-generatedID-14"><div role="heading" class="note-title marker" id="h-note-14" aria-level="4"><span>Note</span></div><p class="">
This should trigger <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#texttracklist-texttracklist">TextTrackList</a></code> [<cite><a class="bibref" data-link-type="biblio" href="#bib-html" title="HTML Standard">HTML</a></cite>] logic to <a href="https://www.w3.org/TR/html51/webappapis.html#queuing">queue a task</a> to fire a <a href="https://www.w3.org/TR/html51/infrastructure.html#trusted">trusted event</a> named <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-texttracklist-onremovetrack">removetrack</a></code>, that does not bubble and is not cancelable, and that uses the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#trackevent-trackevent">TrackEvent</a></code> interface, with the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-trackevent-track">track</a></code> attribute initialized to the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#texttrack-texttrack">TextTrack</a></code> object, at the <var>SourceBuffer textTracks list</var>.
If the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-texttrack-mode">mode</a></code> attribute on the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#texttrack-texttrack">TextTrack</a></code> object was <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-texttrackmode-showing">"showing"</a></code> or <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-texttrackmode-hidden">"hidden"</a></code> at the beginning of this removal step, then this should also trigger <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#texttracklist-texttracklist">TextTrackList</a></code> [<cite><a class="bibref" data-link-type="biblio" href="#bib-html" title="HTML Standard">HTML</a></cite>] logic to <a href="https://www.w3.org/TR/html51/webappapis.html#queuing">queue a task</a> to <a href="https://www.w3.org/TR/html51/infrastructure.html#fire">fire a simple event</a> named <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-texttracklist-onchange">change</a></code> at the <var>SourceBuffer textTracks list</var>.
</p></div>
</li>
</ol>
</li>
</ol>
</li>
<li>If <var>sourceBuffer</var> is in <code><a href="#dom-mediasource-activesourcebuffers">activeSourceBuffers</a></code>, then remove <var>sourceBuffer</var> from <code><a href="#dom-mediasource-activesourcebuffers">activeSourceBuffers</a></code> and
<a href="https://www.w3.org/TR/html51/webappapis.html#queuing">queue a task</a> to <a href="https://www.w3.org/TR/html51/infrastructure.html#fire">fire a simple event</a> named <code><a href="#dom-evt-removesourcebuffer">removesourcebuffer</a></code> at the <a href="#dom-sourcebufferlist" class="internalDFN" data-link-type="idl" id="ref-for-dom-sourcebufferlist-5"><code>SourceBufferList</code></a> returned by <code><a href="#dom-mediasource-activesourcebuffers">activeSourceBuffers</a></code>.</li>
<li>Remove <var>sourceBuffer</var> from <code><a href="#dom-mediasource-sourcebuffers">sourceBuffers</a></code> and <a href="https://www.w3.org/TR/html51/webappapis.html#queuing">queue a task</a> to <a href="https://www.w3.org/TR/html51/infrastructure.html#fire">fire a simple event</a> named <code><a href="#dom-evt-removesourcebuffer">removesourcebuffer</a></code> at
the <a href="#dom-sourcebufferlist" class="internalDFN" data-link-type="idl" id="ref-for-dom-sourcebufferlist-6"><code>SourceBufferList</code></a> returned by <code><a href="#dom-mediasource-sourcebuffers">sourceBuffers</a></code>.</li>
<li>Destroy all resources for <var>sourceBuffer</var>.</li>
</ol></dd><dt><dfn data-export="" data-dfn-type="method" id="dom-mediasource-endofstream" data-idl="operation" data-title="endOfStream" data-dfn-for="MediaSource" data-type="undefined" data-lt="endOfStream()|endOfStream(error)" data-local-lt="MediaSource.endOfStream|MediaSource.endOfStream()|endOfStream"><code>endOfStream</code></dfn></dt><dd>
<p>Signals the end of the stream.</p>
<table class="parameters"><tbody><tr><th>Parameter</th><th>Type</th><th>Nullable</th><th>Optional</th><th>Description</th></tr><tr><td class="prmName">error</td><td class="prmType"><code>EndOfStreamError</code></td><td class="prmNullFalse"><span role="img" aria-label="False">✘</span></td><td class="prmOptTrue"><span role="img" aria-label="True">✔</span></td><td class="prmDesc"></td></tr></tbody></table><div><em>Return type: </em><code><a href="https://www.w3.org/TR/WebIDL-1/#idl-void" class="idlType">void</a></code></div><p>When this method is invoked, the user agent must run the following steps:</p><ol class="method-algorithm">
<li>If the <a data-link-type="idl" href="#dom-mediasource-readystate" class="internalDFN" id="ref-for-dom-mediasource-readystate-9"><code><code>readyState</code></code></a> attribute is not in the <code><a href="#dom-readystate-open">"open"</a></code> state then throw an <code><a href="https://www.w3.org/TR/WebIDL-1/#invalidstateerror">InvalidStateError</a></code> exception and abort these steps.</li>
<li>If the <code><a href="#dom-sourcebuffer-updating">updating</a></code> attribute equals true on any <a href="#dom-sourcebuffer" class="internalDFN" data-link-type="idl" id="ref-for-dom-sourcebuffer-23"><code>SourceBuffer</code></a> in <code><a href="#dom-mediasource-sourcebuffers">sourceBuffers</a></code>, then throw an <code><a href="https://www.w3.org/TR/WebIDL-1/#invalidstateerror">InvalidStateError</a></code> exception and abort these steps.</li>
<li>Run the <a href="#end-of-stream-algorithm">end of stream algorithm</a> with the <var>error</var> parameter set to <var>error</var>.</li>
</ol></dd><dt><dfn data-export="" data-dfn-type="method" id="dom-mediasource-setliveseekablerange" data-idl="operation" data-title="setLiveSeekableRange" data-dfn-for="MediaSource" data-type="undefined" data-lt="setLiveSeekableRange()|setLiveSeekableRange(start, end)" data-local-lt="MediaSource.setLiveSeekableRange|MediaSource.setLiveSeekableRange()|setLiveSeekableRange"><code>setLiveSeekableRange</code></dfn></dt><dd>
<p>Updates the <var><a href="#live-seekable-range">live seekable range</a></var> variable used in <a href="#htmlmediaelement-extensions">HTMLMediaElement Extensions</a> to modify <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-seekable">HTMLMediaElement.seekable</a></code> behavior.</p>
<table class="parameters">
<tbody>
<tr>
<th>Parameter</th>
<th>Type</th>
<th>Nullable</th>
<th>Optional</th>
<th>Description</th>
</tr>
<tr>
<td class="prmName">start</td>
<td class="prmType"><code><a href="https://www.w3.org/TR/WebIDL-1/#idl-double">double</a></code></td>
<td class="prmNullFalse"><span aria-label="False" role="img">✘</span></td>
<td class="prmOptFalse"><span aria-label="False" role="img">✘</span></td>
<td class="prmDesc">The start of the range, in seconds measured from <a href="#presentation-start-time">presentation start time</a>. While set, and if <code><a href="#dom-mediasource-duration">duration</a></code> equals positive Infinity, <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-seekable">HTMLMediaElement.seekable</a></code> will return a non-empty TimeRanges object with a lowest range start timestamp no greater than <var>start</var>.</td>
</tr>
<tr>
<td class="prmName">end</td>
<td class="prmType"><code><a href="https://www.w3.org/TR/WebIDL-1/#idl-double">double</a></code></td>
<td class="prmNullFalse"><span aria-label="False" role="img">✘</span></td>
<td class="prmOptFalse"><span aria-label="False" role="img">✘</span></td>
<td class="prmDesc">The end of range, in seconds measured from <a href="#presentation-start-time">presentation start time</a>. While set, and if <code><a href="#dom-mediasource-duration">duration</a></code> equals positive Infinity, <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-seekable">HTMLMediaElement.seekable</a></code> will return a non-empty TimeRanges object with a highest range end timestamp no less than <var>end</var>.</td>
</tr>
</tbody>
</table>
<div><em>Return type: </em><code><a href="https://www.w3.org/TR/WebIDL-1/#idl-void" class="idlType">void</a></code></div><p>When this method is invoked, the user agent must run the following steps:</p><ol class="method-algorithm">
<li>If the <a data-link-type="idl" href="#dom-mediasource-readystate" class="internalDFN" id="ref-for-dom-mediasource-readystate-10"><code><code>readyState</code></code></a> attribute is not <code><a href="#dom-readystate-open">"open"</a></code> then throw an <code><a href="https://www.w3.org/TR/WebIDL-1/#invalidstateerror">InvalidStateError</a></code> exception and abort these steps.</li>
<li>If <var>start</var> is negative or greater than <var>end</var>, then throw a <code>TypeError</code> exception and abort these steps.</li>
<li>Set <var><a href="#live-seekable-range">live seekable range</a></var> to be a new <a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#normalized-timeranges-object">normalized TimeRanges object</a> containing a single range whose start position is <var>start</var> and end position is <var>end</var>.
</li></ol></dd><dt><dfn data-export="" data-dfn-type="method" id="dom-mediasource-clearliveseekablerange" data-idl="operation" data-title="clearLiveSeekableRange" data-dfn-for="MediaSource" data-type="undefined" data-lt="clearLiveSeekableRange()" data-local-lt="MediaSource.clearLiveSeekableRange|MediaSource.clearLiveSeekableRange()|clearLiveSeekableRange"><code>clearLiveSeekableRange</code></dfn></dt><dd>
<p>Updates the <var><a href="#live-seekable-range">live seekable range</a></var> variable used in <a href="#htmlmediaelement-extensions">HTMLMediaElement Extensions</a> to modify <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-seekable">HTMLMediaElement.seekable</a></code> behavior.</p>
<div><em>No parameters.</em></div><div><em>Return type: </em><code><a href="https://www.w3.org/TR/WebIDL-1/#idl-void" class="idlType">void</a></code></div><p>When this method is invoked, the user agent must run the following steps:</p><ol class="method-algorithm">
<li>If the <a data-link-type="idl" href="#dom-mediasource-readystate" class="internalDFN" id="ref-for-dom-mediasource-readystate-11"><code><code>readyState</code></code></a> attribute is not <code><a href="#dom-readystate-open">"open"</a></code> then throw an <code><a href="https://www.w3.org/TR/WebIDL-1/#invalidstateerror">InvalidStateError</a></code> exception and abort these steps.</li>
<li>If <var><a href="#live-seekable-range">live seekable range</a></var> contains a range, then set <var><a href="#live-seekable-range">live seekable range</a></var> to be a new empty <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#timeranges-timeranges">TimeRanges</a></code> object.
</li></ol></dd><dt><dfn data-export="" data-dfn-type="method" id="dom-mediasource-istypesupported" data-idl="operation" data-title="isTypeSupported" data-dfn-for="MediaSource" data-type="boolean" data-lt="isTypeSupported()|isTypeSupported(type)" data-local-lt="MediaSource.isTypeSupported|MediaSource.isTypeSupported()|isTypeSupported"><code>isTypeSupported</code></dfn>, static</dt><dd>
<p>Check to see whether the <a href="#dom-mediasource" class="internalDFN" data-link-type="idl" id="ref-for-dom-mediasource-14"><code>MediaSource</code></a> is capable of creating <a href="#dom-sourcebuffer" class="internalDFN" data-link-type="idl" id="ref-for-dom-sourcebuffer-24"><code>SourceBuffer</code></a> objects for the specified MIME type.</p>
<div class="note" role="note" id="issue-container-generatedID-15"><div role="heading" class="note-title marker" id="h-note-15" aria-level="4"><span>Note</span></div><p class="">
If true is returned from this method, it only indicates that the <a href="#dom-mediasource" class="internalDFN" data-link-type="idl" id="ref-for-dom-mediasource-15"><code>MediaSource</code></a> implementation is capable of creating <a href="#dom-sourcebuffer" class="internalDFN" data-link-type="idl" id="ref-for-dom-sourcebuffer-25"><code>SourceBuffer</code></a> objects for the specified MIME type. An <code><a href="#dom-mediasource-addsourcebuffer">addSourceBuffer()</a></code> call <em class="rfc2119">SHOULD</em> still fail if sufficient resources are not available to support the addition of a new <a href="#dom-sourcebuffer" class="internalDFN" data-link-type="idl" id="ref-for-dom-sourcebuffer-26"><code>SourceBuffer</code></a>.
</p></div>
<div class="note" role="note" id="issue-container-generatedID-16"><div role="heading" class="note-title marker" id="h-note-16" aria-level="4"><span>Note</span></div><p class="">
This method returning true implies that HTMLMediaElement.canPlayType() will return "maybe" or "probably" since it does not make sense for a <a href="#dom-mediasource" class="internalDFN" data-link-type="idl" id="ref-for-dom-mediasource-16"><code>MediaSource</code></a> to support a type the HTMLMediaElement knows it cannot play.
</p></div>
<table class="parameters"><tbody><tr><th>Parameter</th><th>Type</th><th>Nullable</th><th>Optional</th><th>Description</th></tr><tr><td class="prmName">type</td><td class="prmType"><code><a href="https://www.w3.org/TR/WebIDL-1/#idl-DOMString">DOMString</a></code></td><td class="prmNullFalse"><span role="img" aria-label="False">✘</span></td><td class="prmOptFalse"><span role="img" aria-label="False">✘</span></td><td class="prmDesc"></td></tr></tbody></table><div><em>Return type: </em><code><a href="https://www.w3.org/TR/WebIDL-1/#idl-boolean" class="idlType">boolean</a></code></div><p>When this method is invoked, the user agent must run the following steps:</p><ol class="method-algorithm">
<li>If <var>type</var> is an empty string, then return false.</li>
<li>If <var>type</var> does not contain a valid MIME type string, then return false.</li>
<li>If <var>type</var> contains a media type or media subtype that the MediaSource does not support, then return false.</li>
<li>If <var>type</var> contains a codec that the MediaSource does not support, then return false.</li>
<li>If the MediaSource does not support the specified combination of media type, media subtype, and codecs then return false.</li>
<li>Return true.</li>
</ol></dd></dl>
</section>
<section id="mediasource-events">
<h3 id="x2-3-event-summary"><bdi class="secno">2.3 </bdi>Event Summary<a class="self-link" aria-label="§" href="#mediasource-events"></a></h3>
<table class="old-table">
<thead>
<tr>
<th>Event name</th>
<th>Interface</th>
<th>Dispatched when...</th>
</tr>
</thead>
<tbody>
<tr>
<td><dfn id="dom-evt-sourceopen"><code>sourceopen</code></dfn></td>
<td><code>Event</code></td>
<td><a data-link-type="idl" href="#dom-mediasource-readystate" class="internalDFN" id="ref-for-dom-mediasource-readystate-12"><code><code>readyState</code></code></a> transitions from <code><a href="#dom-readystate-closed">"closed"</a></code> to <code><a href="#dom-readystate-open">"open"</a></code> or from <code><a href="#dom-readystate-ended">"ended"</a></code> to <code><a href="#dom-readystate-open">"open"</a></code>.</td>
</tr>
<tr>
<td><dfn id="dom-evt-sourceended"><code>sourceended</code></dfn></td>
<td><code>Event</code></td>
<td><a data-link-type="idl" href="#dom-mediasource-readystate" class="internalDFN" id="ref-for-dom-mediasource-readystate-13"><code><code>readyState</code></code></a> transitions from <code><a href="#dom-readystate-open">"open"</a></code> to <code><a href="#dom-readystate-ended">"ended"</a></code>.</td>
</tr>
<tr>
<td><dfn id="dom-evt-sourceclose"><code>sourceclose</code></dfn></td>
<td><code>Event</code></td>
<td><a data-link-type="idl" href="#dom-mediasource-readystate" class="internalDFN" id="ref-for-dom-mediasource-readystate-14"><code><code>readyState</code></code></a> transitions from <code><a href="#dom-readystate-open">"open"</a></code> to <code><a href="#dom-readystate-closed">"closed"</a></code> or <code><a href="#dom-readystate-ended">"ended"</a></code> to <code><a href="#dom-readystate-closed">"closed"</a></code>.</td>
</tr>
</tbody>
</table>
</section>
<section id="mediasource-algorithms">
<h3 id="x2-4-algorithms"><bdi class="secno">2.4 </bdi>Algorithms<a class="self-link" aria-label="§" href="#mediasource-algorithms"></a></h3>
<section id="mediasource-attach">
<h4 id="x2-4-1-attaching-to-a-media-element"><bdi class="secno">2.4.1 </bdi>Attaching to a media element<a class="self-link" aria-label="§" href="#mediasource-attach"></a></h4>
<p> A <a href="#dom-mediasource" class="internalDFN" data-link-type="idl" id="ref-for-dom-mediasource-17"><code>MediaSource</code></a> object can be attached to a media element by assigning a <a href="#mediasource-object-url">MediaSource object URL</a> to the media element <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#element-attrdef-media-src">src</a></code> attribute or the src attribute of a <source> inside a media element. A <a href="#mediasource-object-url">MediaSource object URL</a> is created by passing a MediaSource object to <code><a href="#dom-url-createobjecturl">createObjectURL()</a></code>.</p>
<p>If the <a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#resource-fetch-algorithm">resource fetch algorithm</a> was invoked with
a media provider object that is a MediaSource object or a URL record whose object is a MediaSource object,
then let mode be local, skip the first step in the <a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#resource-fetch-algorithm">resource fetch algorithm</a>
(which may otherwise set mode to remote) and add the steps and clarifications below to the <span>"<i>Otherwise (mode is local)</i>"</span> section of the <a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#resource-fetch-algorithm">resource fetch algorithm</a>.
</p><div class="note" role="note" id="issue-container-generatedID-17"><div role="heading" class="note-title marker" id="h-note-17" aria-level="5"><span>Note</span></div><p class="">The <a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#resource-fetch-algorithm">resource fetch algorithm</a>'s first step is expected to eventually align with selecting local mode for URL records whose objects are media provider objects. The intent is that if the HTMLMediaElement's <code>src</code> attribute or selected child <code><source></code>'s <code>src</code> attribute is a <code>blob:</code> URL matching a <a href="#mediasource-object-url">MediaSource object URL</a> when the respective <code>src</code> attribute was last changed, then that MediaSource object is used as the media provider object and current media resource in the local mode logic in the <a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#resource-fetch-algorithm">resource fetch algorithm</a>. This also means that the remote mode logic that includes observance of any preload attribute is skipped when a MediaSource object is attached. Even with that eventual change to [<cite><a class="bibref" data-link-type="biblio" href="#bib-html" title="HTML Standard">HTML</a></cite>], the execution of the following steps at the beginning of the local mode logic is still required when the current media resource is a MediaSource object.</p></div>
<div class="note" role="note" id="issue-container-generatedID-18"><div role="heading" class="note-title marker" id="h-note-18" aria-level="5"><span>Note</span></div><p class="">Relative to the action which triggered the media element's resource selection algorithm, these steps are asynchronous. The resource fetch algorithm is run after the task that invoked the resource selection algorithm is allowed to continue and a stable state is reached. Implementations may delay the steps in the "<i>Otherwise</i>" clause, below, until the MediaSource object is ready for use.</p></div>
<dl class="switch">
<dt>If <a data-link-type="idl" href="#dom-mediasource-readystate" class="internalDFN" id="ref-for-dom-mediasource-readystate-15"><code><code>readyState</code></code></a> is NOT set to <code><a href="#dom-readystate-closed">"closed"</a></code></dt>
<dd>Run the <span>"<i>If the media data cannot be fetched at all, due to network errors, causing the user agent to give up trying to fetch the resource</i>"</span> steps of the <a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#resource-fetch-algorithm">resource fetch algorithm</a>'s <a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#media-data-processing-steps-list">media data processing steps list</a>.</dd>
<dt>Otherwise</dt>
<dd>
<ol>
<li>Set the media element's <a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#delaying-the-load-event-flag">delaying-the-load-event-flag</a> to false.</li>
<li>Set the <a data-link-type="idl" href="#dom-mediasource-readystate" class="internalDFN" id="ref-for-dom-mediasource-readystate-16"><code><code>readyState</code></code></a> attribute to <code><a href="#dom-readystate-open">"open"</a></code>.</li>
<li>
<a href="https://www.w3.org/TR/html51/webappapis.html#queuing">Queue a task</a> to <a href="https://www.w3.org/TR/html51/infrastructure.html#fire">fire a simple event</a> named <code><a href="#dom-evt-sourceopen">sourceopen</a></code> at the <a href="#dom-mediasource" class="internalDFN" data-link-type="idl" id="ref-for-dom-mediasource-18"><code>MediaSource</code></a>.</li>
<li>Continue the <a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#resource-fetch-algorithm">resource fetch algorithm</a> by running the remaining <span>"<i>Otherwise (mode is local)</i>"</span> steps, with these clarifications:
<ol>
<li>Text in the <a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#resource-fetch-algorithm">resource fetch algorithm</a> or the <a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#media-data-processing-steps-list">media data processing steps list</a> that refers to "the download", "bytes received", or "whenever new data for the current media resource becomes available" refers to data passed in via <code><a href="#dom-sourcebuffer-appendbuffer">appendBuffer()</a></code>.</li>
<li>References to HTTP in the <a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#resource-fetch-algorithm">resource fetch algorithm</a> and the <a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#media-data-processing-steps-list">media data processing steps list</a> do not apply because the HTMLMediaElement does not fetch media data via HTTP when a <a href="#dom-mediasource" class="internalDFN" data-link-type="idl" id="ref-for-dom-mediasource-19"><code>MediaSource</code></a> is attached.</li>
</ol>
</li>
</ol>
</dd>
</dl>
<div class="note" role="note" id="issue-container-generatedID-19"><div role="heading" class="note-title marker" id="h-note-19" aria-level="5"><span>Note</span></div><p class="">An attached MediaSource does not use the remote mode steps in the <a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#resource-fetch-algorithm">resource fetch algorithm</a>, so the media element will not fire "suspend" events. Though future versions of this specification will likely remove "progress" and "stalled" events from a media element with an attached MediaSource, user agents conforming to this version of the specification may still fire these two events as these [<cite><a class="bibref" data-link-type="biblio" href="#bib-html" title="HTML Standard">HTML</a></cite>] references changed after implementations of this specification stabilized.</p></div>
</section>
<section id="mediasource-detach">
<h4 id="x2-4-2-detaching-from-a-media-element"><bdi class="secno">2.4.2 </bdi>Detaching from a media element<a class="self-link" aria-label="§" href="#mediasource-detach"></a></h4>
<p>The following steps are run in any case where the media element is going to transition to <a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-network_empty">NETWORK_EMPTY</a> and <a href="https://www.w3.org/TR/html51/webappapis.html#queuing">queue a task</a> to <a href="https://www.w3.org/TR/html51/infrastructure.html#fire">fire a simple event</a> named <a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#eventdef-media-emptied">emptied</a> at the media element. These steps <em class="rfc2119">SHOULD</em> be run right before the transition.</p>
<ol>
<li>Set the <a data-link-type="idl" href="#dom-mediasource-readystate" class="internalDFN" id="ref-for-dom-mediasource-readystate-17"><code><code>readyState</code></code></a> attribute to <code><a href="#dom-readystate-closed">"closed"</a></code>.</li>
<li>Update <code><a href="#dom-mediasource-duration">duration</a></code> to NaN.</li>
<li>Remove all the <a href="#dom-sourcebuffer" class="internalDFN" data-link-type="idl" id="ref-for-dom-sourcebuffer-27"><code>SourceBuffer</code></a> objects from <code><a href="#dom-mediasource-activesourcebuffers">activeSourceBuffers</a></code>.</li>
<li>
<a href="https://www.w3.org/TR/html51/webappapis.html#queuing">Queue a task</a> to <a href="https://www.w3.org/TR/html51/infrastructure.html#fire">fire a simple event</a> named <code><a href="#dom-evt-removesourcebuffer">removesourcebuffer</a></code> at <code><a href="#dom-mediasource-activesourcebuffers">activeSourceBuffers</a></code>.</li>
<li>Remove all the <a href="#dom-sourcebuffer" class="internalDFN" data-link-type="idl" id="ref-for-dom-sourcebuffer-28"><code>SourceBuffer</code></a> objects from <code><a href="#dom-mediasource-sourcebuffers">sourceBuffers</a></code>.</li>
<li>
<a href="https://www.w3.org/TR/html51/webappapis.html#queuing">Queue a task</a> to <a href="https://www.w3.org/TR/html51/infrastructure.html#fire">fire a simple event</a> named <code><a href="#dom-evt-removesourcebuffer">removesourcebuffer</a></code> at <code><a href="#dom-mediasource-sourcebuffers">sourceBuffers</a></code>.</li>
<li>
<a href="https://www.w3.org/TR/html51/webappapis.html#queuing">Queue a task</a> to <a href="https://www.w3.org/TR/html51/infrastructure.html#fire">fire a simple event</a> named <code><a href="#dom-evt-sourceclose">sourceclose</a></code> at the <a href="#dom-mediasource" class="internalDFN" data-link-type="idl" id="ref-for-dom-mediasource-20"><code>MediaSource</code></a>.</li>
</ol>
<div class="note" role="note" id="issue-container-generatedID-20"><div role="heading" class="note-title marker" id="h-note-20" aria-level="5"><span>Note</span></div><p class="">Going forward, this algorithm is intended to be externally called and run in any case where the attached <a href="#dom-mediasource" class="internalDFN" data-link-type="idl" id="ref-for-dom-mediasource-21"><code>MediaSource</code></a>, if any, must be detached from the media element. It <em class="rfc2119">MAY</em> be called on HTMLMediaElement [<cite><a class="bibref" data-link-type="biblio" href="#bib-html" title="HTML Standard">HTML</a></cite>] operations like load() and resource fetch algorithm failures in addition to, or in place of, when the media element transitions to <a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-network_empty">NETWORK_EMPTY</a>. Resource fetch algorithm failures are those which abort either the resource fetch algorithm or the resource selection algorithm, with the exception that the "Final step" [<cite><a class="bibref" data-link-type="biblio" href="#bib-html" title="HTML Standard">HTML</a></cite>] is not considered a failure that triggers detachment.</p></div>
</section>
<section id="mediasource-seeking">
<h4 id="x2-4-3-seeking"><bdi class="secno">2.4.3 </bdi>Seeking<a class="self-link" aria-label="§" href="#mediasource-seeking"></a></h4>
<p>Run the following steps as part of the "<i>Wait until the user agent has established whether or not the media data for the new playback position is available, and, if it is, until it has decoded enough data to play back that position"</i> step of the <a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#seek">seek algorithm</a>:</p>
<ol>
<li>
<div class="note" role="note" id="issue-container-generatedID-21"><div role="heading" class="note-title marker" id="h-note-21" aria-level="5"><span>Note</span></div><p class="">The media element looks for <a href="#media-segment">media segments</a> containing the <var>new playback position</var> in each <a href="#dom-sourcebuffer" class="internalDFN" data-link-type="idl" id="ref-for-dom-sourcebuffer-29"><code>SourceBuffer</code></a> object in <code><a href="#dom-mediasource-activesourcebuffers">activeSourceBuffers</a></code>.
Any position within a <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#timeranges-timeranges">TimeRange</a></code> in the current value of the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-buffered">HTMLMediaElement.buffered</a></code> attribute has all necessary media segments buffered for that position.</p></div>
<dl class="switch">
<dt>If <var>new playback position</var> is not in any <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#timeranges-timeranges">TimeRange</a></code> of <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-buffered">HTMLMediaElement.buffered</a></code></dt>
<dd>
<ol>
<li>If the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-readystate">HTMLMediaElement.readyState</a></code> attribute is greater than
<code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-have_metadata">HAVE_METADATA</a></code>, then set the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-readystate">HTMLMediaElement.readyState</a></code> attribute
to <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-have_metadata">HAVE_METADATA</a></code>.
<div class="note" role="note" id="issue-container-generatedID-22"><div role="heading" class="note-title marker" id="h-note-22" aria-level="5"><span>Note</span></div><p class="">Per <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#ready-states">HTMLMediaElement ready states</a></code> [<cite><a class="bibref" data-link-type="biblio" href="#bib-html" title="HTML Standard">HTML</a></cite>] logic, <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-readystate">HTMLMediaElement.readyState</a></code> changes may trigger events on the HTMLMediaElement.</p></div>
</li>
<li>The media element waits until an <code><a href="#dom-sourcebuffer-appendbuffer">appendBuffer()</a></code> call causes the <a href="#sourcebuffer-coded-frame-processing">coded frame processing algorithm</a> to set
the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-readystate">HTMLMediaElement.readyState</a></code> attribute to a value greater than <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-have_metadata">HAVE_METADATA</a></code>.
<div class="note" role="note" id="issue-container-generatedID-23"><div role="heading" class="note-title marker" id="h-note-23" aria-level="5"><span>Note</span></div><p class="">The web application can use <code><a href="#dom-sourcebuffer-buffered">buffered</a></code> and <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-buffered">HTMLMediaElement.buffered</a></code> to determine what the media element needs to resume playback.</p></div>
</li>
</ol>
</dd>
<dt>Otherwise</dt>
<dd>Continue
<div class="note" role="note" id="issue-container-generatedID-24"><div role="heading" class="note-title marker" id="h-note-24" aria-level="5"><span>Note</span></div><p class="">If the <a data-link-type="idl" href="#dom-mediasource-readystate" class="internalDFN" id="ref-for-dom-mediasource-readystate-18"><code><code>readyState</code></code></a> attribute is <code><a href="#dom-readystate-ended">"ended"</a></code> and the <var>new playback position</var> is within a <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#timeranges-timeranges">TimeRange</a></code> currently in <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-buffered">HTMLMediaElement.buffered</a></code>, then the seek operation must continue to completion here even if one or more currently selected or enabled track buffers' largest range end timestamp is less than <var>new playback position</var>. This condition should only occur due to logic in <code><a href="#dom-sourcebuffer-buffered">buffered</a></code> when <a data-link-type="idl" href="#dom-mediasource-readystate" class="internalDFN" id="ref-for-dom-mediasource-readystate-19"><code><code>readyState</code></code></a> is <code><a href="#dom-readystate-ended">"ended"</a></code>.</p></div>
</dd>
</dl>
</li>
<li>The media element resets all decoders and initializes each one with data from the appropriate <a href="#init-segment">initialization segment</a>.</li>
<li>The media element feeds <a href="#coded-frame">coded frames</a> from the <a href="#active-track-buffers">active track buffers</a> into the decoders starting with the
closest <a href="#random-access-point">random access point</a> before the <var>new playback position</var>.</li>
<li>Resume the <a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#seek">seek algorithm</a> at the "<i>Await a stable state</i>" step.</li>
</ol>
</section>
<section id="buffer-monitoring">
<h4 id="x2-4-4-sourcebuffer-monitoring"><bdi class="secno">2.4.4 </bdi>SourceBuffer Monitoring<a class="self-link" aria-label="§" href="#buffer-monitoring"></a></h4>
<p>The following steps are periodically run during playback to make sure that all of the <a href="#dom-sourcebuffer" class="internalDFN" data-link-type="idl" id="ref-for-dom-sourcebuffer-30"><code>SourceBuffer</code></a> objects in <code><a href="#dom-mediasource-activesourcebuffers">activeSourceBuffers</a></code> have <a href="#enough-data">enough data to ensure uninterrupted playback</a>. Changes to <code><a href="#dom-mediasource-activesourcebuffers">activeSourceBuffers</a></code> also cause these steps to run because they affect the conditions that trigger state transitions.</p>
<p>Having <dfn id="enough-data">enough data to ensure uninterrupted playback</dfn> is an implementation specific condition where the user agent
determines that it currently has enough data to play the presentation without stalling for a meaningful period of time. This condition is
constantly evaluated to determine when to transition the media element into and out of the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-have_enough_data">HAVE_ENOUGH_DATA</a></code> ready state.
These transitions indicate when the user agent believes it has enough data buffered or it needs more data respectively.</p>
<div class="note" role="note" id="issue-container-generatedID-25"><div role="heading" class="note-title marker" id="h-note-25" aria-level="5"><span>Note</span></div><p class="">An implementation <em class="rfc2119">MAY</em> choose to use bytes buffered, time buffered, the append rate, or any other metric it sees fit to
determine when it has enough data. The metrics used <em class="rfc2119">MAY</em> change during playback so web applications <em class="rfc2119">SHOULD</em> only rely on the value of
<code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-readystate">HTMLMediaElement.readyState</a></code> to determine whether more data is needed or not.</p></div>
<div class="note" role="note" id="issue-container-generatedID-26"><div role="heading" class="note-title marker" id="h-note-26" aria-level="5"><span>Note</span></div><p class="">When the media element needs more data, the user agent <em class="rfc2119">SHOULD</em> transition it from <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-have_enough_data">HAVE_ENOUGH_DATA</a></code> to
<code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-have_future_data">HAVE_FUTURE_DATA</a></code> early enough for a web application to be able to respond without causing an interruption in playback.
For example, transitioning when the current playback position is 500ms before the end of the buffered data gives the application roughly
500ms to append more data before playback stalls.</p></div>
<dl class="switch">
<dt>If the the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-readystate">HTMLMediaElement.readyState</a></code> attribute equals <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-have_nothing">HAVE_NOTHING</a></code>:</dt>
<dd>
<ol>
<li>Abort these steps.</li>
</ol>
</dd>
<dt>If <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-buffered">HTMLMediaElement.buffered</a></code> does not contain a <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#timeranges-timeranges">TimeRange</a></code> for the current playback position:</dt>
<dd>
<ol>
<li>Set the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-readystate">HTMLMediaElement.readyState</a></code> attribute to <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-have_metadata">HAVE_METADATA</a></code>.
<div class="note" role="note" id="issue-container-generatedID-27"><div role="heading" class="note-title marker" id="h-note-27" aria-level="5"><span>Note</span></div><p class="">Per <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#ready-states">HTMLMediaElement ready states</a></code> [<cite><a class="bibref" data-link-type="biblio" href="#bib-html" title="HTML Standard">HTML</a></cite>] logic, <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-readystate">HTMLMediaElement.readyState</a></code> changes may trigger events on the HTMLMediaElement.</p></div></li>
<li>Abort these steps.</li>
</ol>
</dd>
<dt>If <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-buffered">HTMLMediaElement.buffered</a></code> contains a <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#timeranges-timeranges">TimeRange</a></code> that includes the current playback position and <a href="#enough-data">enough data to ensure uninterrupted playback</a>:</dt>
<dd>
<ol>
<li>Set the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-readystate">HTMLMediaElement.readyState</a></code> attribute to <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-have_enough_data">HAVE_ENOUGH_DATA</a></code>.
<div class="note" role="note" id="issue-container-generatedID-28"><div role="heading" class="note-title marker" id="h-note-28" aria-level="5"><span>Note</span></div><p class="">Per <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#ready-states">HTMLMediaElement ready states</a></code> [<cite><a class="bibref" data-link-type="biblio" href="#bib-html" title="HTML Standard">HTML</a></cite>] logic, <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-readystate">HTMLMediaElement.readyState</a></code> changes may trigger events on the HTMLMediaElement.</p></div></li>
<li>Playback may resume at this point if it was previously suspended by a transition to <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-have_current_data">HAVE_CURRENT_DATA</a></code>.</li>
<li>Abort these steps.</li>
</ol>
</dd>
<dt>If <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-buffered">HTMLMediaElement.buffered</a></code> contains a <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#timeranges-timeranges">TimeRange</a></code> that includes the current playback position and some time beyond the current playback position, then run the following steps:</dt>
<dd>
<ol>
<li>Set the <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-readystate">HTMLMediaElement.readyState</a></code> attribute to <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-have_future_data">HAVE_FUTURE_DATA</a></code>.
<div class="note" role="note" id="issue-container-generatedID-29"><div role="heading" class="note-title marker" id="h-note-29" aria-level="5"><span>Note</span></div><p class="">Per <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#ready-states">HTMLMediaElement ready states</a></code> [<cite><a class="bibref" data-link-type="biblio" href="#bib-html" title="HTML Standard">HTML</a></cite>] logic, <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-readystate">HTMLMediaElement.readyState</a></code> changes may trigger events on the HTMLMediaElement.</p></div>
</li>
<li>Playback may resume at this point if it was previously suspended by a transition to <code><a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#dom-htmlmediaelement-have_current_data">HAVE_CURRENT_DATA</a></code>.</li>