Skip to content

Set HeaderExtensionsToNegotiate after negotiation #238

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 6 commits into from
Sep 25, 2025
Merged

Set HeaderExtensionsToNegotiate after negotiation #238

Changes from all commits
Commits
Show all changes
6 commits
Select commit Hold shift + click to select a range
6e443a8
Set HeaderExtensionsToNegotiate after negotiation
alvestrand Aug 14, 2025
129b3e5
Also initialize new transceivers
alvestrand Aug 21, 2025
8178166
Add transport-consistent initialization
alvestrand Aug 21, 2025
f2f8bd0
Review comment fix
alvestrand Sep 4, 2025
1623cd9
Minor tweaks and notes
alvestrand Sep 23, 2025
1970624
Fix reference error
alvestrand Sep 24, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
30 changes: 28 additions & 2 deletions index.html
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -159,14 +159,32 @@ <h3>
</p>
<ol>
<li>
<p>Set {{RTCRtpTransceiver/[[HeaderExtensionsToNegotiate]]}} to the
<p>If transceivers of the same kind exist in the current PeerConnection,
copy {{RTCRtpTransceiver/[[HeaderExtensionsToNegotiate]]}} from
the first such transceiver, in the order defined by the [=CollectTransceivers=] algorithm.
This ensures consistency across transceivers if they are added
after initial negotiation.
</p>
<p>If no such transceiver exists, set {{RTCRtpTransceiver/[[HeaderExtensionsToNegotiate]]}} to the
platform-specific list of implemented RTP header extensions. The
{{RTCRtpHeaderExtensionCapability/direction}} attribute for all
extensions that are mandatory to use MUST be initialized to an
appropriate value other than {{RTCRtpTransceiverDirection/"stopped"}}.
The {{RTCRtpHeaderExtensionCapability/direction}} attribute for
extensions that will not be offered by default in an initial offer MUST
be initialized to {{RTCRtpTransceiverDirection/"stopped"}}.</p>
be initialized to {{RTCRtpTransceiverDirection/"stopped"}}.</p>
<p>
If there are header extensions whose state needs to be consistent across all transceivers
in a bundle,
and any other transceiver exists that will be included in the same bundle,
copy the {{RTCRtpHeaderExtensionCapability/direction}} attribute
for that extension from that other transceiver.
Copy link
Contributor

@youennf youennf Sep 11, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Maybe add an example to illustrate the usefulness of the mechanism

</p>
<p class="note">An example of header extensions that need to be identical across all
media sections is the key management extensions from [[RFC4567]], as described in section 5.35 of
[[RFC8859]], where they have category IDENTICAL. If this is supported and negotiated as "sendrecv",
and a new transceiver is added, that transceiver needs to also have the extension as "sendrecv".
</p>
<p class="note">The list of header extensions that MUST/SHOULD be
supported is listed in [[RTCWEB-RTP]], section 5.2. The "mid" extension
is mandatory to use when BUNDLE is in use, per [[BUNDLE]] section
Expand Down Expand Up @@ -230,6 +248,14 @@ <h2>Modifications to existing procedures</h2>
<var>transceiver</var>.{{RTCRtpTransceiver/[[NegotiatedHeaderExtensions]]}}
to <var>negotiatedExtensions</var>.</p>
</li>
<li>
<p>
Set <var>transceiver</var>.{{RTCRtpTransceiver/[[HeaderExtensionsToNegotiate]]}}
to <var>negotiatedExtensions</var>.
This ensures that unless further calls to {{RTCRtpTransceiver/setHeaderExtensionsToNegotiate}} are done,
subsequent offer/answer will not alter the list of extensions.
</p>
</li>
</ol>
</li>
</ul>
Expand Down