Transferable MediaStreamTrack (Media Capture and Streams Extension)

[jan-ivar]

Request for Mozilla Position on an Emerging Web Specification

• Specification title: § 5.1 Transferable MediaStreamTrack, from Media Capture and Streams Extensions
• Specification or proposal URL (if available): https://w3c.github.io/mediacapture-extensions/#transferable-mediastreamtrack
• Explainer URL (if available):
• Proposal author(s) (@-mention GitHub accounts): @youennf
• Caniuse.com URL (optional):
• Bugzilla URL (optional): https://bugs.webkit.org/show_bug.cgi?id=267682, https://bugzil.la/1749543
• Mozillians who can provide input (optional): @jan-ivar
• WebKit standards-position:

Other information

Filed from news in https://webkit.org/blog/15443/news-from-wwdc24-webkit-in-safari-18-beta:

WebKit for Safari 18 beta adds support for MediaStreamTrack processing in a dedicated worker.

Transfer of MST is a prerequisite for the APIs MediaStreamTrackProcessor and VideoTrackGenerator, which in the spec are only exposed in DedicatedWorker.

[jan-ivar]

I'm supportive of this API as it gets JS processing of the browser's media pipeline off the main thread.

This seems the right approach, and avoids relying on optimizations like https://github.com/whatwg/streams/issues/1124.