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Adding mediadiscarded event #29

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Adding mediadiscarded event #29

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ced40d7
Keep it clean
martinthomson Oct 31, 2014
8462311
Adding mediadiscarded event
martinthomson Nov 5, 2014
8cfd8e6
Adding mediadiscarded to the change log
martinthomson Nov 5, 2014
097c95e
Expanding context around media discard.
martinthomson Dec 1, 2014
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91 changes: 88 additions & 3 deletions webrtc.html
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Original file line number Diff line number Diff line change
Expand Up @@ -10,11 +10,11 @@
<meta content="text/html; charset=us-ascii" http-equiv="Content-Type">
<script class="remove" src="http://www.w3.org/Tools/respec/respec-w3c-common"
type="text/javascript">
// // keep this comment //
// // keep this comment //
</script>
<script class="remove" src="webrtc.js" type="text/javascript">
// // keep
this comment //
this comment //
</script>
</head>

Expand Down Expand Up @@ -539,7 +539,7 @@ <h4>Operation</h4>

<p class="note">The creation of new incoming
<code>MediaStream</code>s may be triggered either by SDP
negotiation or by the receipt of media on a given flow.
negotiation or by the receipt of media on a given flow.
<!-- [[OPEN ISSUE: How many <code>MediaStream</code>s are created
when you receive multiple conflicting pranswers?]] --></p>
</li>
Expand Down Expand Up @@ -1595,6 +1595,39 @@ <h3>Interface Definition</h3>
"#dom-peerconnection-ice-connection-state"><code>RTCPeerConnection</code>
ice connection state</a> changes.
</dd>

<dt>attribute EventHandler ondiscardedmedia</dt>

<dd>
<p>This event handler, of event handler event
type <code><a href="#event-discardedmedia">discardedmedia</a></code>,
MUST be fired by all objects implementing the
<code><a>RTCPeerConnection</a></code> interface. It is fired when
inbound media is discarded.</p>

<p>Media can be discarded by <code><a>RTCPeerConnection</a></code>
for a number of reasons. Media packets that arrive from an answerer.
Media packets that are successfully authenticated but can't be
attributed to a <code>MediaStreamTrack</code>, can't be decoded, or
have any other error also cause this event to fire. Unauthenticated
packets are always silently discarded.</p>

<p>Media packets for an SSRC that has been recently discarded SHOULD
be discarded without generating
a <code><a href="#event-discardedmedia">discardedmedia</a></code>
event. This event MAY be suppressed entirely if the <a>user
agent</a> determines that too many events of this type are being
generated.</p>

<p class="note">This event might be delayed while there is an
outstanding offer (i.e., in a <a href=
"#dom-peerconnection-signaling-state"><code>signalingState</code></a>
of <code>have-local-offer</code>
or <code>have-remote-pranswer</code>), since packets corresponding
to an answer might arrive prior to the answer that describes them.
In these states, unknown media might be buffered temporarily to
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Should we not spec this out? Either that no event is fired if there is an expected answer coming, or that it is delayed for up to x seconds or something.

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#39 opened

allow time for an answer to arrive.</p>
</dd>
</dl>
</section>

Expand Down Expand Up @@ -1891,6 +1924,46 @@ <h4>RTCSdpError</h4>
</ul>
</div>
</section>

<section>
<h4>RTCMediaDiscardedEvent</h4>

<p>The <code>mediadiscarded</code> event of the <code>RTCPeerConnection</code> uses
the <code><a>RTCMediaDiscardedEvent</a></code> interface.</p>

<p><dfn title="Fire a media discarded event">Firing an
<code><a>RTCMediaDiscardedEvent</a></code> event named
<var>e</var></dfn> means that an event with the name <var>e</var>,
which does not bubble (except where otherwise stated) and is not
cancelable (except where otherwise stated), and which uses the
<code>RTCMediaDiscardedEvent</code> interface MUST be created and
dispatched at the given target.</p>

<dl class="idl" data-merge="RTCMediaDiscardedEventInit"
title="interface RTCMediaDiscardedEvent : Event">
<dt>Constructor(DOMString type, RTCMediaDiscardedEventInit
eventInitDict)</dt>

<dt>readonly attribute unsigned long ssrc</dt>
<dd>The Synchronization source (SSRC) number of the packet.</dd>

<dt>readonly attribute unsigned byte payloadType</dt>
<dd>The RTP payload type of the packet.</dd>

<dt>readonly attribute DOMString? mid</dt>
<dd>The value of any mid header extension on the discarded media
packet, if that header is present.</dd>
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Since text above says that this is not fired once for every packet, what are the rules for multi-packet notifications? Do they contain data from the first packet? An exemplar packet picked at random? An aggregation of discarded packets?
I think number of discarded packets belongs in stats, not in the event, though.

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We have a proposal for discardedPackets in stats, which is described as packets that arrived early or late and are discarded by the dejitter buffer, however in this case it would be because it cannot assign it to the correct dejitter buffer.

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@alvestrand ,

what are the rules for multi-packet notifications? Do they contain data from the first packet? An exemplar packet picked at random? An aggregation of discarded packets?

This is written as though the first packet generates the event and subsequent packets (with the same SSRC) are simply discarded. I think that is correct. I imagine that the browser could add more information about the stream if the first packet had no header extension and later ones did, but I'm happy to leave that out from a requirement perspective.

</dl>

<dl class="idl" title="dictionary RTCMediaDiscardedEventInit : EventInit">
<dt>unsigned long ssrc</dt>
<dd>See <a><code>RTCMediaDiscardedEvent.ssrc</code></a></dd>
<dt>unsigned byte payloadType</dt>
<dd>See <a><code>RTCMediaDiscardedEvent.payloadType</code></a></dd>
<dt>DOMString mid</dt>
<dd>See <a><code>RTCMediaDiscardedEvent.mid</code></a></dd>
</dl>
</section>
</section>

<section>
Expand Down Expand Up @@ -4993,6 +5066,17 @@ <h2>Event summary</h2>
the script when an IdP encounters an error while validating an
identity assertion.</td>
</tr>

<tr>
<td><dfn id=
"event-discardedmedia"><code>discardedmedia</code></dfn></td>

<td><code><a>RTCMediaDiscardedEvent</a></code></td>

<td>
Unhandled media was discarded.
</td>
</tr>
</tbody>
</table>

Expand Down Expand Up @@ -5072,6 +5156,7 @@ <h3>Changes since June 4, 2014</h3>

<ol>
<li>Bug 25724: Allow garbage collection of closed PeerConnections</li>
<li>Bug 21877: Adding mediadiscarded event</li>
</ol>

<h3>Changes since April 10, 2014</h3>
Expand Down