Intent to Prototype: DisplayMediaStreamConstraints.systemAudio

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Elad Alon

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May 25, 2022, 8:37:55 AM5/25/22

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Summary

Hint indicating to the user agent whether the application, upon calling getDisplayMedia() with {audio: true} or similar, wishes *system audio* to be offered to the user. (If not - only offer tab-audio.)

Blink component

Blink

Motivation

User agents may offer audio to be captured alongside video, if the application specifies {audio: true}, or maps audio to anything else that's different from false. But not all audio is created alike. Consider video-conferencing applications. Tab-audio is often useful, and can be shared with remote participants. But system-audio includes participants' own audio, and it is NOT desirable to share it back. State of the art? VC applications can ask for "audio", use it if it's tab-audio, and discard it otherwise. This works, but it's sub-optimal. The user is left confused. The user wanted to share system-audio, the user was offered to share-system, the user explicitly approved sharing system-audio - and now remote participants are telling the user that they can't, in fact, hear the system-audio. Now how confusing is that?! It’s better to allow applications to ask for less - allow the application to ask for non-system audio.

Initial public proposal

https://github.com/w3c/mediacapture-screen-share/issues/219

TAG review

N/A. This is just an addition of a single flag to an existing dictionary, following well-known patterns.

TAG review status

Not applicable

Risks

Interoperability and Compatibility

Gecko: Positive (https://github.com/mozilla/standards-positions/issues/638) Jan-Ivar Bruaroey from Mozilla, and Youenn Fablet from Apple, have both collaborated with us closely in shaping this PR. They have then approved merging this PR into w3c/mediacapture-screen-share. This is implicit support, so I'd consider it POSITIVE even though, as of the time of this writing, the official request for position has not yet been answered.

WebKit: Positive (https://lists.webkit.org/pipermail/webkit-dev/2022-May/032247.html) Jan-Ivar Bruaroey from Mozilla, and Youenn Fablet from Apple, have both collaborated with us closely in shaping this PR. They have then approved merging this PR into w3c/mediacapture-screen-share. This is implicit support, so I'd consider it POSITIVE even though, as of the time of this writing, the official request for position has not yet been answered.

Web developers: Positive Endorsed by Google Meet.

Other signals:

Security

This feature can only be used by Web applications to REDUCE the amount of private information they obtain from the user. As such, this is a net security gain.

WebView application risks

N/A

Debuggability

N/A

Is this feature fully tested by web-platform-tests?

Tracking bug

https://bugs.chromium.org/p/chromium/issues/detail?id=1329129

Estimated milestones

No milestones specified

Anticipated spec changes

N/A

Link to entry on the Chrome Platform Status

https://chromestatus.com/feature/4649448880734208

This intent message was generated by Chrome Platform Status.

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