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Add onssrcchange/oncsrcchange events to RTCRtpReceiver #243

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b5b0fd3
Add onssrcchange/oncsrcchange events to RTCRtpReceiver.
henbos Sep 26, 2025
621b604
nit wording tweak
henbos Sep 29, 2025
46f46c2
nit: latest
henbos Sep 29, 2025
155f72c
Clarify decode
henbos Oct 23, 2025
34e8a32
Update index.html
henbos Oct 23, 2025
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79 changes: 77 additions & 2 deletions index.html
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Original file line number Diff line number Diff line change
Expand Up @@ -1448,6 +1448,56 @@ <h2>
</section>
</section>
</section>
<section id="source-change-event">
<h2>
{{RTCRtpReceiver}} extensions
</h2>
<p>
The {{RTCRtpReceiver}} interface and {{RTCRtpContributingSource}} and {{RTCRtpSynchronizationSource}}
dictionaries are defined in [[WEBRTC]]. This document extends this interface by
adding two event handlers that fire when the {{RTCRtpContributingSource/source}} of
{{RTCRtpReceiver/getSynchronizationSources()}} or {{RTCRtpReceiver/getContributingSources()}} changes.
</p>
<p>
By listening to these events, apps can react more quickly to source changes than if they were polling
these APIs, enabling the UX to be updated more quickly in response to virtual SSRCs changing which is
a common way for apps to keep track of which participant's media is currently being played out.
</p>
<pre class="idl">partial interface RTCRtpReceiver {
attribute EventHandler onssrcchange;
attribute EventHandler oncsrcchange;
};</pre>
<p>
Whenever the {{RTCRtpContributingSource/source}} identifier is updated based on the last decoded frame,
the [= user agent =] MUST [= queue a task =] to [= fire an event =] named {{RTCRtpReceiver/ssrcchange}}
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In the same queued task ... append the following steps at the end: 1. fire ssrcchange if changed, 2. fire csrcchange if changed

if the SSRC changed and an event named {{RTCRtpReceiver/csrcchange}} if the CSRC changed. If both
identifiers are changed based on the same decoded frame, both events fire in the same queued task. This
ensures that both SSRC and CSRC information is exposed to the app at the same time.
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at the time of the first event

</p>
<h3>
Attributes
</h3>
<dl data-link-for="RTCRtpReceiver" data-dfn-for="RTCRtpReceiver" class="attributes">
<dt>
<dfn id="dom-rtptransceiver-onssrcchange">onssrcchange</dfn> of type {{EventHandler}}
</dt>
<dd>
<p>
Fired when the {{RTCRtpContributingSource/source}} in {{RTCRtpReceiver/getSynchronizationSources()}}
changes, see above.
</p>
</dd>
<dt>
<dfn id="dom-rtptransceiver-oncsrcchange">oncsrcchange</dfn> of type {{EventHandler}}
</dt>
<dd>
<p>
Fired when the {{RTCRtpContributingSource/source}} in {{RTCRtpReceiver/getContributingSources()}}
changes, see above.
</p>
</dd>
</dl>
</section>
<section id="disable-hardware">
<h2>Disabling hardware acceleration</h2>
<p>
Expand Down Expand Up @@ -1526,8 +1576,7 @@ <h3>Modifications to existing procedures</h3>
</section>
<section class="informative">
<h2>Event summary</h2>
<p>
The following events fire on {{RTCIceTransport}} objects:</p>
<p>The following events fire on {{RTCIceTransport}} objects:</p>
<table class="simple">
<thead>
<tr>
Expand Down Expand Up @@ -1561,6 +1610,32 @@ <h2>Event summary</h2>
</tr>
</tbody>
</table>
<p>The following events fire on {{RTCRtpReceiver}} objects:</p>
<table class="simple">
<thead>
<tr>
<th>Event name</th>
<th>Interface</th>
<th>Fired when...</th>
</tr>
</thead>
<tbody>
<tr>
<th scope=row><dfn data-dfn-for="RTCRtpReceiver" data-dfn-type=event>ssrcchange</dfn></th>
<td>{{Event}}</td>
<td>
The SSRC identifier changed in response to an RTP packet.
</td>
</tr>
<tr>
<th scope=row><dfn data-dfn-for="RTCRtpReceiver" data-dfn-type=event>csrcchange</dfn></th>
<td>{{Event}}</td>
<td>
The CSRC identifier changed in response to an RTP packet.
</td>
</tr>
</tbody>
</table>
</section>
<section>
<h2>Timestamp behavior</h2>
Expand Down