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Add support for MediaStreamTrack being Serializable #24

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Add support for MediaStreamTrack being Serializable #24

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59ca120
Serializable extension
alvestrand May 20, 2021
3cf4cd3
Some more cleanup and explanations
alvestrand May 20, 2021
dc11b76
Formatting nits
alvestrand May 20, 2021
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58 changes: 57 additions & 1 deletion index.html
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Expand Up @@ -9,7 +9,7 @@
// See https://github.com/w3c/respec/wiki/ for how to configure ReSpec
var respecConfig = {
group: "webrtc",
xref: ["html", "infra", "permissions", "dom", "mediacapture-streams", "webidl"],
xref: ["html", "infra", "permissions", "dom", "mediacapture-streams", "webaudio", "webidl"],
edDraftURI: "https://w3c.github.io/mediacapture-extensions/",
editors: [
{name: "Jan-Ivar Bruaroey", company: "Mozilla Corporation", w3cid: 79152},
Expand Down Expand Up @@ -347,5 +347,61 @@ <h2>Examples</h2>
</pre>
</div>
</section>
<section>
<h2>Serializable MediaStreamTrack</h2>
<div>
<p>A {{MediaStreamTrack}} is a <a data-cite="!HTML/#serializable-objects">serializable object</a>.
This allows manipulating real-time media outside the context it was requested or created in, for instance in workers or third-party iframes.</p>
<p>
To preserve the existing privacy and security infrastructure, in particular for capture tracks,
a transferred track remains tightly bound to the original source.</p>
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s/transferred/serialized/

<p>
In particular, for the case of cameras and microphones, which are tightly bound to their original context, any track that
is bound to that source will be ended immediately when that context goes away.
</p>
</div>
<div>
<p>The WebIDL changes are the following:
<pre class="idl"
>[Exposed=(Window,Worker,AudioWorklet), Serializable]
partial interface MediaStreamTrack {
// Remove partial once we figure out how to do it without creating respec warnings.
// No change to MediaStreamTrack exposed API.
};</pre>
</div>
<div>
<p>At creation of a {{MediaStreamTrack}} object, called <var>track</var>, run the following steps:</p>
<ol>
<li><p>Initialize <var>track</var>.`[[IsDetached]]` to <code>false</code>.</p></li>
</ol>
</div>
<div>
<p>The {{MediaStreamTrack}} <a data-cite="!HTML/#serialization-steps">transfer steps</a>, given <var>value</var> and <var>dataHolder</var>, are:</p>
<ol>
<li><p>If <var>value</var>.`[[IsDetached]]` is <code>true</code>, throw a "DataCloneError" DOMException.</p></li>
<li><p>Set <var>dataHolder</var>.`[[id]]` to <var>value</var>.{{MediaStreamTrack/id}}.</p></li>
<li><p>Set <var>dataHolder</var>.`[[kind]]` to <var>value</var>.{{MediaStreamTrack/kind}}.</p></li>
<li><p>Set <var>dataHolder</var>.`[[label]]` to <var>value</var>.{{MediaStreamTrack/label}}.</p></li>
<li><p>Set <var>dataHolder</var>.`[[readyState]]` to <var>value</var>.{{MediaStreamTrack/readyState}}.</p></li>
<li><p>Set <var>dataHolder</var>.`[[enabled]]` to <var>value</var>.{{MediaStreamTrack/enabled}}.</p></li>
<li><p>Set <var>dataHolder</var>.`[[muted]]` to <var>value</var>.{{MediaStreamTrack/muted}}.</p></li>
<li><p>Set <var>dataHolder</var>.`[[source]]` to <var>value</var> underlying source.</p></li>
<li><p>Set <var>dataHolder</var>.`[[constraints]]` to <var>value</var> active constraints.</p></li>
</ol>
</div>
<div><p>{{MediaStreamTrack}} <a data-cite="!HTML/#deserialization-steps">deserialization steps</a>, given <var>dataHolder</var> and <var>track</var>, are:</p>
<ol>
<li><p>Initialize <var>track</var>.{{MediaStreamTrack/id}} to <var>dataHolder</var>.`[[id]]`.</p></li>
<li><p>Initialize <var>track</var>.{{MediaStreamTrack/kind}} to <var>dataHolder</var>.`[[kind]]`.</p></li>
<li><p>Initialize <var>track</var>.{{MediaStreamTrack/label}} to <var>dataHolder</var>.`[[label]]`.</p></li>
<li><p>Initialize <var>track</var>.{{MediaStreamTrack/readyState}} to <var>dataHolder</var>.`[[readyState]]`.</p></li>
<li><p>Initialize <var>track</var>.{{MediaStreamTrack/enabled}} to <var>dataHolder</var>.`[[enabled]]`.</p></li>
<li><p>Initialize <var>track</var>.{{MediaStreamTrack/muted}} to <var>dataHolder</var>.`[[muted]]`.</p></li>
<li><p>Initialize <var>track</var> underlying source to <var>dataHolder</var>.`[[source]]`.</p></li>
<li><p>Set <var>track</var>'s constraints to <var>dataHolder</var>.`[[constraints]]`.</p></li>
</ol>
</div>
</section>
</body>
</html>