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Update codec match algorithm to be more general (work with AV1) #3043

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merged 2 commits into from
Mar 27, 2025
Merged

Update codec match algorithm to be more general (work with AV1) #3043

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51f3f29
Update codec match algorithm to be more general (work with AV1)
henbos Mar 27, 2025
dbe38ee
Update WPT PR reference
henbos Mar 27, 2025
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16 changes: 16 additions & 0 deletions amendments.json
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Original file line number Diff line number Diff line change
Expand Up @@ -587,5 +587,21 @@
"web-platform-tests/wpt#49990"
]
}
],
"codec-match-asymmetrical": [
{
"description": "Compare symmetrical or asymmetrical parameters (not just level-id)",
"type": "correction",
"status": "candidate",
"difftype": "modify",
"id": 53,
"pr": 3043,
"tests": [
"webrtc/protocol/av1-profile-asymmetry.https.html"
],
"testUpdates": [
"web-platform-tests/wpt#51637"
]
}
]
}
1 change: 1 addition & 0 deletions base-rec.html
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Expand Up @@ -11400,6 +11400,7 @@ <h1 id="title" class="title">WebRTC: Real-Time Communication in Browsers</h1>
</p></div>
</li>
<li class="needs-tests">
<div id="codec-match-asymmetrical"></div>
<p>
If <var>firstMediaFormat</var> is not equal to <var>secondMediaFormat</var>, return
<code>false</code>.
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51 changes: 28 additions & 23 deletions webrtc.html
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Expand Up @@ -2819,8 +2819,9 @@ <h4>
<p>For each <var>encoding</var> in
<var>transceiver</var>.{{RTCRtpTransceiver/[[Sender]]}}.{{RTCRtpSender/[[SendEncodings]]}},
if <var>encoding</var>.{{RTCRtpEncodingParameters/codec}} does not match any entry in
<var>codecs</var>, using the [= codec dictionary match =] algorithm with <var>ignoreLevels</var>
set to <code>true</code>, [=map/remove=] <var>encoding</var>.{{RTCRtpEncodingParameters/codec}}.</p>
<var>codecs</var>, using the [= codec dictionary match =] algorithm with
<var>ignoreAsymmetricalParameters</var> set to <code>true</code>, [=map/remove=]
<var>encoding</var>.{{RTCRtpEncodingParameters/codec}}.</p>
</li>
</ol>
</li>
Expand Down Expand Up @@ -3749,8 +3750,8 @@ <h2>
exclude any codecs not included in the
[=RTCRtpSender/list of implemented send codecs=] for
<var>kind</var>, using the [= codec dictionary match =]
algorithm with <var>ignoreLevels</var> set to
<code>true</code>.</p>
algorithm with <var>ignoreAsymmetricalParameters</var>
set to <code>true</code>.</p>
</p>
</li>
<li>
Expand All @@ -3762,8 +3763,8 @@ <h2>
exclude any codecs not included in the
[=list of implemented receive codecs=] for
<var>kind</var>, using the [= codec dictionary match =]
algorithm with <var>ignoreLevels</var> set to
<code>true</code>.
algorithm with <var>ignoreAsymmetricalParameters</var>
set to <code>true</code>.
</p>
</li>
</ol>
Expand Down Expand Up @@ -4036,8 +4037,8 @@ <h2>
exclude any codecs not included in the
[=RTCRtpSender/list of implemented send codecs=] for
<var>kind</var>, using the [= codec dictionary match =]
algorithm with <var>ignoreLevels</var> set to
<code>true</code>.
algorithm with <var>ignoreAsymmetricalParameters</var>
set to <code>true</code>.
</p>
</li>
<li>
Expand All @@ -4049,8 +4050,8 @@ <h2>
exclude any codecs not included in the
[=list of implemented receive codecs=] for
<var>kind</var>, using the [= codec dictionary match =]
algorithm with <var>ignoreLevels</var> set to
<code>true</code>.
algorithm with <var>ignoreAsymmetricalParameters</var>
set to <code>true</code>.
</p>
</li>
</ol>
Expand Down Expand Up @@ -9097,7 +9098,7 @@ <h2>
<li id="setparameters-codec-validation-4">
Any <var>encoding</var> in encodings [=map/exists|contains=] a codec
not found in <var>choosableCodecs</var>, using the [= codec dictionary match =]
algorithm with <var>ignoreLevels</var> set to <code>true</code>.
algorithm with <var>ignoreAsymmetricalParameters</var> set to <code>true</code>.
</li>
</ul>
</li>
Expand Down Expand Up @@ -9819,7 +9820,7 @@ <h2>
When {{codec}} is set and {{RTCRtpSender/[[SendCodecs]]}} have been negotiated,
the user agent SHOULD use the first {{RTCRtpSender/[[SendCodecs]]}} matching
{{codec}} for sending, according to the [= codec dictionary match =] algorithm
with <var>ignoreLevels</var> set to <code>true</code>.
with <var>ignoreAsymmetricalParameters</var> set to <code>true</code>.
</p>
</dd>
</div>
Expand Down Expand Up @@ -11498,8 +11499,8 @@ <h2>
<p>
The <dfn class="export">codec dictionary match</dfn> algorithm given two
{{RTCRtpCodec}} dictionaries <var>first</var> and <var>second</var>, and
an <var>ignoreLevels</var> boolean defaulting to <code>false</code> if not
specified, is as follows:
an <var>ignoreAsymmetricalParameters</var> boolean defaulting to
<code>false</code> if not specified, is as follows:
</p>
</div>
<ol class=algorithm>
Expand Down Expand Up @@ -11562,21 +11563,25 @@ <h2>
</p>
</li>
<li>
<div id="codec-match-asymmetrical">
<p>
If <var>firstMediaFormat</var> is not equal to <var>secondMediaFormat</var>, return
<code>false</code>.
If the media configurations described by <var>firstMediaFormat</var> and
<var>secondMediaFormat</var> are not compatible, meaning they contain symmetrical
parameters that are not equal, return <code>false</code>.
</p>
<p class="note">
Which parameters are symmetrical or asymmetrical is codec-specific. For example,
AV1's profile, level-idx and tier parameters may all be asymmetrical between the
offerer and answerer while H.265's profile-id needs to be symmetrical and its
level-id may be asymmetrical.
</p>
</li>
<li>
<div id="codec-match-without-level-id">
<p>
If <var>ignoreLevels</var> is <code>false</code> and the highest complying bitstream
levels inferred from <var>first</var>.{{RTCRtpCodec/sdpFmtpLine}} and
<var>second</var>.{{RTCRtpCodec/sdpFmtpLine}} are different, return <code>false</code>.
</p>
<p class="note">
Even if <var>ignoreLevels</var> is <code>true</code>, some codecs (such as H.264) include
levels in the media format, so that ignoring the level requires codec-specific parsing.
If <var>ignoreAsymmetricalParameters</var> is <code>false</code> and any parameter
is not equal between <var>firstMediaFormat</var> and <var>secondMediaFormat</var>,
return <code>false</code>. This includes comparing the asymmetrical parameters.
</p>
</div>
</li>
Expand Down