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Bug 27758 - Add informative reference to INBANDTRACKS and track attri…
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…bute sourcing requirements.
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acolwell committed Jan 9, 2015
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21 changes: 14 additions & 7 deletions index.html
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</p>
<h1 class="title p-name" id="title" property="dcterms:title">Media Source Extensions</h1>

<h2 property="dcterms:issued" datatype="xsd:dateTime" content="2015-01-09T18:20:42.000Z" id="w3c-editor-s-draft-09-january-2015"><abbr title="World Wide Web Consortium">W3C</abbr> Editor's Draft <time class="dt-published" datetime="2015-01-09">09 January 2015</time></h2>
<h2 property="dcterms:issued" datatype="xsd:dateTime" content="2015-01-09T19:20:10.000Z" id="w3c-editor-s-draft-09-january-2015"><abbr title="World Wide Web Consortium">W3C</abbr> Editor's Draft <time class="dt-published" datetime="2015-01-09">09 January 2015</time></h2>
<dl>

<dt>This version:</dt>
Expand Down Expand Up @@ -2806,17 +2806,23 @@ <h3 aria-level="2" role="heading" id="h3_sourcebufferlist-events"><span class="s
<p>This section provides general requirements for all byte stream format specifications:</p>
<ul>
<li>A byte stream format specification must define <a href="#init-segment">initialization segments</a> and <a href="#media-segment">media segments</a>.</li>
<li>A byte stream format should provide references for sourcing <a href="#idl-def-AudioTrack" class="idlType"><code>AudioTrack</code></a>, <a href="#idl-def-VideoTrack" class="idlType"><code>VideoTrack</code></a>, and <a href="#idl-def-TextTrack" class="idlType"><code>TextTrack</code></a> attribute values
from data in <a href="#init-segment">initialization segments</a>.
<div class="note"><div class="note-title" aria-level="2" role="heading" id="h_note_47"><span>Note</span></div><p class="">If the byte stream format covers a format similar to one covered in the in-band tracks spec [<cite><a class="bibref" href="#bib-INBANDTRACKS">INBANDTRACKS</a></cite>], then
it should try to use the same attribute mappings so that Media Source Extensions playback and non-Media Source Extensions playback provide the
same track information.</p></div>
</li>
<li>It must be possible to identify segment boundaries and segment type (initialization or media) by examining the byte stream alone.</li>
<li>The user agent must run the <a href="#sourcebuffer-append-error">append error algorithm</a> with the <var>decode error</var> parameter set to true when any of the following conditions are met:
<ol>
<li>
<p>The number and type of tracks are not consistent.</p>
<div class="note"><div class="note-title" aria-level="2" role="heading" id="h_note_47"><span>Note</span></div><p class="">For example, if the first <a href="#init-segment">initialization segment</a> has 2 audio tracks and 1 video track, then all <a href="#init-segment">initialization segments</a> that follow it in the byte stream must describe 2 audio tracks and 1 video track.</p></div>
<div class="note"><div class="note-title" aria-level="2" role="heading" id="h_note_48"><span>Note</span></div><p class="">For example, if the first <a href="#init-segment">initialization segment</a> has 2 audio tracks and 1 video track, then all <a href="#init-segment">initialization segments</a> that follow it in the byte stream must describe 2 audio tracks and 1 video track.</p></div>
</li>
<li><a href="#track-id">Track IDs</a> are not the same across <a href="#init-segment">initialization segments</a>, for segments describing multiple tracks of a single type. (e.g. 2 audio tracks).</li>
<li>
<p>Codecs changes across <a href="#init-segment">initialization segments</a>.</p>
<div class="note"><div class="note-title" aria-level="2" role="heading" id="h_note_48"><span>Note</span></div><p class="">For example, a byte stream that starts with an <a href="#init-segment">initialization segment</a> that specifies a single AAC track and later contains an <a href="#init-segment">initialization segment</a> that specifies a single AMR-WB track is not allowed. Support for multiple codecs is handled with multiple <a href="#idl-def-SourceBuffer" class="idlType"><code>SourceBuffer</code></a> objects.</p></div>
<div class="note"><div class="note-title" aria-level="2" role="heading" id="h_note_49"><span>Note</span></div><p class="">For example, a byte stream that starts with an <a href="#init-segment">initialization segment</a> that specifies a single AAC track and later contains an <a href="#init-segment">initialization segment</a> that specifies a single AMR-WB track is not allowed. Support for multiple codecs is handled with multiple <a href="#idl-def-SourceBuffer" class="idlType"><code>SourceBuffer</code></a> objects.</p></div>
</li>
</ol>
</li>
Expand All @@ -2825,19 +2831,19 @@ <h3 aria-level="2" role="heading" id="h3_sourcebufferlist-events"><span class="s
<li><a href="#track-id">Track IDs</a> changing across <a href="#init-segment">initialization segments</a> if the segments describes only one track of each type.</li>
<li>
<p>Video frame size changes. The user agent must support seamless playback.</p>
<div class="note"><div class="note-title" aria-level="2" role="heading" id="h_note_49"><span>Note</span></div><p class="">This will cause the &lt;video&gt; display region to change size if the web application does not use CSS or HTML attributes (width/height) to constrain the element size.</p></div>
<div class="note"><div class="note-title" aria-level="2" role="heading" id="h_note_50"><span>Note</span></div><p class="">This will cause the &lt;video&gt; display region to change size if the web application does not use CSS or HTML attributes (width/height) to constrain the element size.</p></div>
</li>
<li>
<p>Audio channel count changes. The user agent may support this seamlessly and could trigger downmixing.</p>
<div class="note"><div class="note-title" aria-level="2" role="heading" id="h_note_50"><span>Note</span></div><p class="">This is a quality of implementation issue because changing the channel count may require reinitializing the audio device, resamplers, and channel mixers which tends to be audible.</p></div>
<div class="note"><div class="note-title" aria-level="2" role="heading" id="h_note_51"><span>Note</span></div><p class="">This is a quality of implementation issue because changing the channel count may require reinitializing the audio device, resamplers, and channel mixers which tends to be audible.</p></div>
</li>
</ol>
</li>
<li>The following rules apply to all <a href="#media-segment">media segments</a> within a byte stream. A user agent must:
<ol>
<li>Map all timestamps to the same <a href="http://www.w3.org/TR/html5/embedded-content-0.html#media-timeline">media timeline</a>.</li>
<li>Support seamless playback of <a href="#media-segment">media segments</a> having a timestamp gap smaller than the audio frame size. User agent must not reflect these gaps in the <code><a href="#widl-SourceBuffer-buffered">buffered</a></code> attribute.
<div class="note"><div class="note-title" aria-level="2" role="heading" id="h_note_51"><span>Note</span></div><p class="">This is intended to simplify switching between audio streams where the frame boundaries don't always line up across encodings (e.g. Vorbis).</p></div>
<div class="note"><div class="note-title" aria-level="2" role="heading" id="h_note_52"><span>Note</span></div><p class="">This is intended to simplify switching between audio streams where the frame boundaries don't always line up across encodings (e.g. Vorbis).</p></div>
</li>
</ol>
</li>
Expand Down Expand Up @@ -3611,5 +3617,6 @@ <h3 aria-level="2" role="heading" id="h3_sourcebufferlist-events"><span class="s
</dd><dt id="bib-HTML5">[HTML5]</dt><dd rel="dcterms:requires">Ian Hickson; Robin Berjon; Steve Faulkner; Travis Leithead; Erika Doyle Navara; Edward O'Connor; Silvia Pfeiffer. <a href="http://www.w3.org/TR/html5/"><cite>HTML5</cite></a>. 28 October 2014. W3C Recommendation. URL: <a href="http://www.w3.org/TR/html5/">http://www.w3.org/TR/html5/</a>
</dd><dt id="bib-TYPED-ARRAYS">[TYPED-ARRAYS]</dt><dd rel="dcterms:requires">David Herman; Kenneth Russell. <a href="https://www.khronos.org/registry/typedarray/specs/latest/"><cite>Typed Array Specification</cite></a>. 26 June 2013. Khronos Working Draft. URL: <a href="https://www.khronos.org/registry/typedarray/specs/latest/">https://www.khronos.org/registry/typedarray/specs/latest/</a>
</dd><dt id="bib-WHATWG-STREAMS-API">[WHATWG-STREAMS-API]</dt><dd rel="dcterms:requires">Domenic Denicola; Takeshi Yoshino. <a href="https://streams.spec.whatwg.org/"><cite>WHATWG Streams API</cite></a>. W3C Working Draft. URL: <a href="https://streams.spec.whatwg.org/">https://streams.spec.whatwg.org/</a>
</dd></dl></section><section id="informative-references" typeof="bibo:Chapter" resource="#informative-references" rel="bibo:Chapter"><h3 aria-level="2" role="heading" id="h3_informative-references"><span class="secno">A.2 </span>Informative references</h3><dl class="bibliography" about=""><dt id="bib-MSE-REGISTRY">[MSE-REGISTRY]</dt><dd rel="dcterms:references">Aaron Colwell. <a href="byte-stream-format-registry.html"><cite>Media Source Extensions Byte Stream Format Registry</cite></a>. URL: <a href="byte-stream-format-registry.html">byte-stream-format-registry.html</a>
</dd></dl></section><section id="informative-references" typeof="bibo:Chapter" resource="#informative-references" rel="bibo:Chapter"><h3 aria-level="2" role="heading" id="h3_informative-references"><span class="secno">A.2 </span>Informative references</h3><dl class="bibliography" about=""><dt id="bib-INBANDTRACKS">[INBANDTRACKS]</dt><dd rel="dcterms:references">Bob Lund; Silvia Pfeiffer. <a href="http://dev.w3.org/html5/html-sourcing-inband-tracks/"><cite>Sourcing In-band Media Resource Tracks from Media Containers into HTML</cite></a>. URL: <a href="http://dev.w3.org/html5/html-sourcing-inband-tracks/">http://dev.w3.org/html5/html-sourcing-inband-tracks/</a>
</dd><dt id="bib-MSE-REGISTRY">[MSE-REGISTRY]</dt><dd rel="dcterms:references">Aaron Colwell. <a href="byte-stream-format-registry.html"><cite>Media Source Extensions Byte Stream Format Registry</cite></a>. URL: <a href="byte-stream-format-registry.html">byte-stream-format-registry.html</a>
</dd></dl></section></section></body></html>
32 changes: 26 additions & 6 deletions isobmff-byte-stream-format-respec.html
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// prevent error messages from being displayed for references to these objects.
definitionMap: {},

postProcess: [ mediaSourcePostProcessor ]
postProcess: [ mediaSourcePostProcessor ],

localBiblio: {
"INBANDTRACKS": {
title: "Sourcing In-band Media Resource Tracks from Media Containers into HTML",
href: "http://dev.w3.org/html5/html-sourcing-inband-tracks/",
authors: ["Bob Lund", "Silvia Pfeiffer"],
publisher: "W3C",
}
}

};
</script>
Expand Down Expand Up @@ -124,7 +133,7 @@ <h2>MIME-type parameters</h2>
<h4>Initialization Segments</h4>
<p>An ISO BMFF <a def-id="init-segment"></a> is defined in this specification as a single File Type Box (<span class="iso-box">ftyp</span>) followed by a single Movie Header Box (<span class="iso-box">moov</span>).</p>

<p>The user agent must run the <a def-id="eos-decode"></a> if any of the following conditions are met:</p>
<p>The user agent must run the <a def-id="append-decode-error-algorithm"></a> if any of the following conditions are met:</p>
<ol>
<li>A File Type Box contains a <span class="iso-var">major_brand</span> or <span class="iso-var">compatible_brand</span> that the user agent does not support.</li>
<li>A box or field in the Movie Header Box is encountered that violates the requirements mandated
Expand All @@ -145,6 +154,9 @@ <h4>Initialization Segments</h4>
<p>Valid top-level boxes such as <span class="iso-box">pdin</span>, <span class="iso-box">free</span>, and <span class="iso-box">sidx</span> are
allowed to appear before the <span class="iso-box">moov</span> box. These boxes must be accepted and ignored by the user agent and are not
considered part of the <a def-id="init-segment"></a> in this specification.</p>

<p>The user agent must source attribute values for id, kind, label and language for <a def-id="audio-track"></a>, <a def-id="video-track"></a> and
<a def-id="text-track"></a> objects as described for MPEG-4 ISOBMFF in the in-band tracks spec [[INBANDTRACKS]].</p>
</section>

<section id="iso-media-segments">
Expand All @@ -161,7 +173,7 @@ <h4>Media Segments</h4>
specification.
</p>

<p>The user agent must run the <a def-id="eos-decode"></a> if any of the following conditions are met:</p>
<p>The user agent must run the <a def-id="append-decode-error-algorithm"></a> if any of the following conditions are met:</p>
<ol>
<li>A box or field in the Movie Fragment Box is encountered that violates the requirements mandated
by the <span class="iso-var">major_brand</span> or one of the
Expand Down Expand Up @@ -212,15 +224,23 @@ <h2>Revision History</h2>
</thead>
<tbody>
<tr>
<td>20 June 2014</td>
<td>09 January 2015</td>
<td>
<ul>
<li>Bug 27758 - Add reference to INBANDTRACKS spec.</li>
</ul>
</td>
</tr>
<tr>
<td><a href="https://rawgit.com/w3c/media-source/163dbff04bcc89e0659bceab65abc409c3ce3895/isobmff-byte-stream-format.html">20 June 2014</a></td>
<td>
<ul>
<li>Bug 26066 - Clarify edit list requirements.</li>
</ul>
</td>
</tr>
<tr>
<td><a href="https://dvcs.w3.org/hg/html-media/raw-file/cad94fce3b90/media-source/isobmff-byte-stream-format.html">03 March 2014</a></td>
<td><a href="https://rawgit.com/w3c/media-source/6a57b8c6e4fde462a69db34e6376ccb77e58683f/isobmff-byte-stream-format.html">03 March 2014</a></td>
<td>
<ul>
<li>Bug 24903 - Add ftyp & styp validation text.</li>
Expand All @@ -229,7 +249,7 @@ <h2>Revision History</h2>
</td>
</tr>
<tr>
<td><a href="https://dvcs.w3.org/hg/html-media/raw-file/190b670254ff/media-source/isobmff-byte-stream-format.html">02 December 2013</a></td>
<td><a href="https://rawgit.com/w3c/media-source/edd2cf21d5779171409b1a78a34ee5b3063543d5/isobmff-byte-stream-format.html">02 December 2013</a></td>
<td>Initial CR version.</td>
</tr>
</tbody>
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