RTCRtpEncodingParameters.scaleResolutionDownTo

[henbos]

WebKittens

@youennf

Title of the proposal

WebRTC extensions, section scaleResolutionDownTo

URL to the spec

https://w3c.github.io/webrtc-extensions/#dom-rtcrtpencodingparameters-scaleresolutiondownto

URL to the spec's repository

No response

Issue Tracker URL

No response

Explainer URL

No response

TAG Design Review URL

No response

Mozilla standards-positions issue URL

mozilla/standards-positions#1071

WebKit Bugzilla URL

No response

Radar URL

No response

Description

This adds a new encoding parameter to WebRTC allowing the app to say which resolution it wants to send in absolute terms ("send 360p") instead of relative terms ("downscale by 2" + frame is 720p), avoiding race conditions when the track dynamically changes size.

Example use case is sending {360p, 720p} simulcast and when dynamically disabling the 720p layer also adjusting the track size to 360p in order to avoid expensive effects processing in 720p when only 360p is sent.

See https://www.w3.org/2024/08/27-webrtc-minutes.html#t06 where this was discussed and approved by the W3C WebRTC WG.