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Add WebRTC-specific interactions with capture/receive/RTP timestamps #224

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handellm
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@handellm handellm commented Sep 20, 2024

This PR changes the spec to describe how WebRTC interacts with timestamps added by w3c/mediacapture-extensions#156.

Related to changes needed by w3c/webcodecs#813


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<p>
<!-- TODO: use the xref mechanism when mediacapture-extensions spec status is cleared up.
See https://github.com/w3c/mediacapture-extensions/issues/132 -->
The following terms are defined in <a href="https://w3c.github.io/mediacapture-extensions">mediacapture-extensions</a>
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Due to the unclear state of the mediacapture-extensions spec (not listed in browser-specs) I had to make some temporary reference structure as per below, when referring to concepts defined there.

@handellm handellm marked this pull request as ready for review December 19, 2024 11:10
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henbos commented Jan 9, 2025

Ping @handellm

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@alvestrand please take another look!

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guidou commented Feb 3, 2025

cc @youennf @jan-ivar

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Looked at in editors meeting Feb 27; will discuss again next week.

Comment on lines +1558 to +1561
<h2>RTCRtpSender video track frame timestamp effects on outgoing packet NTP and RTP timestamps</h2>
<p>
The user agent defines a <dfn class="export">frame timestamp</dfn> being the same as the [=capture timestamp=]
of the frame being produced on the {{RTCRtpSender}} {{MediaStreamTrack}} if it is set.
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Sorry, I'm not following what this timestamp is by the name "frame timestamp". Not all track sources will insert capture timestamps in the tracks they produce. Is this what you mean by "if it is set"?

Comment on lines +1562 to +1563
If it is unset the user agent MUST estimate a timestamp from the sent frame's [=presentation timestamp=] together with the
time it was received by the {{RTCRtpSender}}. This estimate MUST NOT be based on [= RTP timestamp =].
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What does "received by the RTCRtpSender" mean? Do you mean RTCRtpReceiver?

@guidou guidou closed this Apr 3, 2025
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guidou commented Apr 3, 2025

replaced by #233

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5 participants