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Add captureTime, receiveTime and rtpTimestamp to VideoFrameMetadata #813

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merged 3 commits into from
Dec 10, 2024
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Add captureTime, receiveTime and rtpTimestamp to VideoFrameMetadata #813

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250fe3a
Add captureTime, receiveTime and rtpMetadata to VideoFrameMetadata
Jul 5, 2024
a74786c
Update references to mediacapture-extensions.
Nov 12, 2024
3a88a39
Update references
Nov 12, 2024
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12 changes: 12 additions & 0 deletions video_frame_metadata_registry.src.html
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Expand Up @@ -61,6 +61,18 @@
<td>segments</td>
<td>[Human face segmentation](https://w3c.github.io/mediacapture-extensions/#human-face-segmentation)</td>
</tr>
<tr>
<td>captureTime</td>
<td>[Capture time](https://wicg.github.io/video-rvfc/#dom-videoframecallbackmetadata-capturetime)</td>
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@aboba aboba Sep 13, 2024 •
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The RVFC text is too RTP centric to be used here. I'd copy over the text and make some changes. For a WebCodecs application, captureTime can be serialized on the wire and set by a WebCodecs application for frames received from a remote peer. Also, NTP timestamp format does not imply a global clock so change “estimated using clock synchronization” to “aligned to the sender wallclock”.

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The plan is to

  1. Define what the concept "capture time" is in mediacapture-extensions, and define "remote capture time" over at webrtc-extensions (this would refer to the new mediacapture-extensions "capture time" concept plus text copied from rVFC to describe estimation).
  2. Refer to these new definitions here (local tracks: look here; remote webrtc tracks: look here) instead of the rVFC reference, but use DOMHighResTimestamp relative to local Performance.timeOrigin.

That would leave captureTime unset otherwise. A webcodecs app could use whichever out-of-band techniques to compute & set a valid local DOMHighResTimestamp. Does it need to be mentioned in the spec?

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The PR is now updated to reference mediacapture-extensions, where these concepts are now defined.

</tr>
<tr>
<td>receiveTime</td>
<td>[Receive time](https://wicg.github.io/video-rvfc/#dom-videoframecallbackmetadata-receivetime)</td>
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@aboba aboba Sep 13, 2024 •
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Comment: RVFC text is also too WebRTC-centric. Can we allow this to be present in a WebCodecs application as well (set by the receiver)?

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The plan is to describe this as "set for remote webrtc tracks" and use DOMHighResTimestamp relative to local Performance.timeOrigin. I agree it should be settable by a WebCodecs application.

</tr>
<tr>
<td>rtpTimestamp</td>
<td>[RTP timestamp](https://wicg.github.io/video-rvfc/#dom-videoframecallbackmetadata-rtptimestamp)</td>
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The RVFC text is ok here but I'd still probaby copy it over rather than referencing it.

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I planned to define what a "rtp timestamp" is over at webrtc-extensions and simply define here that it's present for "remote webrtc tracks" together with a reference.

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Replaced with the reference to mediacapture-extensions.
Did not copy text to follow the format for Human face segmentation

</tr>
</table>


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