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Filter codecs preferences on transceiver direction #3018

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Filter codecs preferences on transceiver direction #3018

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473e58d
Filter codecs preferences on transceiver direction
henbos Nov 7, 2024
5e55108
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henbos Nov 7, 2024
862c6f8
Fix wording
henbos Nov 7, 2024
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Try to make bot happy
henbos Nov 7, 2024
3f1c705
Address comments
henbos Nov 7, 2024
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Clarify with notes
henbos Nov 8, 2024
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Merge branch 'main' into 241107_CodecDirection
henbos Nov 21, 2024
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14 changes: 7 additions & 7 deletions amendments.json
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Original file line number Diff line number Diff line change
Expand Up @@ -1022,19 +1022,19 @@
"id": 40
}
],
"setcodecpreferences-receive": [
"setcodecpreferences-send-and-receive": [
{
"description": "setCodecPreferences only takes into account receive codecs",
"pr": 2926,
"type": "correction",
"description": "setCodecPreferences supports both send and receive codecs (filtered by direction)",
"pr": 3018,
"type": "addition",
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"status": "candidate",
"tests": [
"webrtc/RTCRtpTransceiver-setCodecPreferences.html"
"webrtc/RTCRtpTransceiver-setCodecPreferences-direction.html"
],
"testUpdates": [
"web-platform-tests/wpt#44318"
"web-platform-tests/wpt#1234"
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Add real test before landing!

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Chromium issue for adding WPTs: https://crbug.com/379551577

],
"id": 42
"id": 50
}
],
"internalslot-jitterbuffertarget": [
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2 changes: 1 addition & 1 deletion base-rec.html
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Expand Up @@ -11036,7 +11036,7 @@ <h4 id="methods-8">
<dfn data-idl="operation" data-export="" data-dfn-type="method" id="dom-rtcrtptransceiver-setcodecpreferences" data-title="setCodecPreferences" data-dfn-for="RTCRtpTransceiver" data-type="undefined" data-lt="setCodecPreferences()|setCodecPreferences(codecs)" data-local-lt="RTCRtpTransceiver.setCodecPreferences|RTCRtpTransceiver.setCodecPreferences()|setCodecPreferences"><code>setCodecPreferences</code></dfn>
</dt>
<dd>
<div id="setcodecpreferences-receive">
<div id="setcodecpreferences-send-and-receive">
<p class="needs-tests">
The <a data-link-type="idl" href="#dom-rtcrtptransceiver-setcodecpreferences" class="internalDFN" id="ref-for-dom-rtcrtptransceiver-setcodecpreferences-4"><code><code>setCodecPreferences</code></code></a> method overrides the default
codec preferences used by the <a href="#dfn-user-agent" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-user-agent-9">user agent</a>. When
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90 changes: 56 additions & 34 deletions webrtc.html
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Expand Up @@ -3727,14 +3727,11 @@ <h2>
</li>
<li>
<p>
The <i>codec preferences</i> of a [= media
description =]'s [= associated =] transceiver,
<var>transceiver</var>, is said to be the value of
<var>transceiver</var>.{{RTCRtpTransceiver/[[PreferredCodecs]]}}
with the following filtering applied (or said not
to be set if
<var>transceiver</var>.{{RTCRtpTransceiver/[[PreferredCodecs]]}}
is empty):
Let <var>filteredCodecs</var> be the result of
applying the following filter on
<var>transceiver</var>.{{RTCRtpTransceiver/[[PreferredCodecs]]}}.
The filtering MUST NOT change the order of the codec
preferences:
</p>
<ol>
<li>
Expand Down Expand Up @@ -3767,8 +3764,11 @@ <h2>
</li>
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</ol>
<p>
The filtering MUST NOT change the order of the
codec preferences.
The <i>codec preferences</i> of a [= media
description =]'s [= associated =] transceiver,
<var>transceiver</var>, is said to be the value of
<var>filteredCodecs</var> if non-empty and said to
be unset otherwise.
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Note to self there is also a reference to preferred codecs internal slots in setParameters that should be filtered on sending

</p>
</li>
<li>
Expand Down Expand Up @@ -4010,14 +4010,11 @@ <h2>
<ol id="create-answer-restrictions">
<li>
<p>
The <i>codec preferences</i> of an m= section's
[= associated =] transceiver,
<var>transceiver</var>, is said to be the value of
<var>transceiver</var>.{{RTCRtpTransceiver/[[PreferredCodecs]]}}
with the following filtering applied (or said not
to be set if
<var>transceiver</var>.{{RTCRtpTransceiver/[[PreferredCodecs]]}}
is empty):
Let <var>filteredCodecs</var> be the result of
applying the following filter on
<var>transceiver</var>.{{RTCRtpTransceiver/[[PreferredCodecs]]}}.
The filtering MUST NOT change the order of the
codec preferences:
</p>
<ol>
<li>
Expand Down Expand Up @@ -4050,8 +4047,11 @@ <h2>
</li>
</ol>
<p>
The filtering MUST NOT change the order of the
codec preferences.
The <i>codec preferences</i> of a [= media
description =]'s [= associated =] transceiver,
<var>transceiver</var>, is said to be the value of
<var>filteredCodecs</var> if non-empty and said to
be unset otherwise.
</p>
</li>
<li>
Expand Down Expand Up @@ -11323,31 +11323,48 @@ <h2>
<dfn data-idl="">setCodecPreferences</dfn>
</dt>
<dd>
<div id="setcodecpreferences-receive">
<div id="setcodecpreferences-send-and-receive">
<p>
The {{setCodecPreferences}} method overrides the default
receive codec preferences used by the <a>user agent</a>. When
codec preferences used by the <a>user agent</a>. When
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user agent "...as input to negotiation"

generating a session description using either
{{RTCPeerConnection/createOffer}} or
{{RTCPeerConnection/createAnswer}}, the <a>user agent</a>
MUST use the indicated codecs, in the order specified in the
<var>codecs</var> argument, for the media section
corresponding to this {{RTCRtpTransceiver}}.
{{RTCPeerConnection/createAnswer}}, the <a>user agent</a> MUST
filter the preferred codecs on {{RTCRtpTransceiver/direction}}
and, if this results in a non-empty list, it MUST use the
specified codecs in the order of the <var>codecs</var>
argument, for the media section corresponding to this
{{RTCRtpTransceiver}}.
</p>
<p>
This method allows applications to disable the negotiation of
specific codecs (including RTX/RED/FEC). It also allows an
application to cause a remote peer to prefer the codec that
appears first in the list for sending.
specific codecs (including RTX/RED/FEC) by listing all codecs
except for the ones to disable.
</p>
<p class="note">
If the m= section is used for receiving, the order of the
codecs in the SDP (both the offer and the answer) tells the
remote endpoint which codec the local endpoint prefers to
receive. The answerer defaults to using the order in the SDP
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Even if the m= section is not used for receiving,

offer, but overrides this with their own codec preferences if
they have any.
</p>
<p class="note">
An RTCRtpSender defaults to sending what the remote endpoint
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Use curly bracket links here and elsewhere

indicated that it prefers to receive, but the application can
change which codec to send amongst negotiated codecs in
setParameters() at any time. An RTCRtpReceiver is prepared to
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Link to "codec" specifically

receive any negotiated codec.
</p>
<!-- 'until this method is called again' is not clear. Ditto for 'any default value' -->
<p class="needs-test">
Codec preferences remain in effect for all calls to
{{RTCPeerConnection/createOffer}} and
{{RTCPeerConnection/createAnswer}} that include this
{{RTCRtpTransceiver}} until this method is called again.
Setting <var>codecs</var> to an empty sequence resets codec
preferences to any default value.
Setting <var>codecs</var> to an empty sequence, or one that
becomes empty after {{RTCRtpTransceiver/direction}} filtering,
results in default codec preferences.
</p>
<p class="note">
Codecs have their payload types listed under each m= section
Expand All @@ -11362,8 +11379,11 @@ <h2>
be removed from the mapping of payload types in the SDP.
</p>
<p>
{{setCodecPreferences}} will reject attempts to set <var>codecs</var>
[= codec dictionary match | not matching =] codecs found in
{{setCodecPreferences}} will reject attempts to set
<var>codecs</var> [= codec dictionary match | not matching =]
codecs found in either
{{RTCRtpSender}}.{{RTCRtpSender/getCapabilities}}(<var>kind</var>)
or
{{RTCRtpReceiver}}.{{RTCRtpReceiver/getCapabilities}}(<var>kind</var>),
where <var>kind</var> is the kind of the
{{RTCRtpTransceiver}} on which the method is called.
Expand Down Expand Up @@ -11405,7 +11425,9 @@ <h2>
</li>
<li class="no-test-needed">
<p>
Let <var>codecCapabilities</var> be
Let <var>codecCapabilities</var> be the union of
{{RTCRtpSender}}.{{RTCRtpSender/getCapabilities}}(<var>kind</var>).{{RTCRtpParameters/codecs}}
and
{{RTCRtpReceiver}}.{{RTCRtpReceiver/getCapabilities}}(<var>kind</var>).{{RTCRtpParameters/codecs}}.
</p>
</li>
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