Intent to Ship: Capture handle

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Elad Alon

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Mar 9, 2022, 5:26:52 AMMar 9
to blink-dev

Contact emails

elad...@chromium.org

Explainer

https://github.com/w3c/mediacapture-handle/blob/main/identity/README.md

Specification

https://w3c.github.io/mediacapture-handle/identity/

Summary

We introduce a mechanism that allows an application to opt-in to exposing certain information to other applications which are video-capturing it. This allows collaboration between capturing and captured applications. For example, a VC application that's video-capturing a tab where a presentation application lives, could expose user-facing controls in the VC tab for navigating the presentation in the captured tab.


TAG review

https://github.com/w3ctag/design-reviews/issues/645

TAG review status

Pending

Risks

Interoperability and Compatibility


Gecko:

Engaged in discussions in the W3C and approved the adoption of this document.

There is currently a disagreement with Mozilla over issue #11. Mozilla suggests setCaptureHandleConfig() should only be callable once, to reduce the risk of it becoming an alternative communication channel. We see relevant use cases that calling it multiple times can enable (e.g. the captured application changing its state and wants to notify the capturer). We believe setCaptureHandleConfig() should be callable multiple times.
Note that there could be other mitigations for Mozilla's concerns (e.g. rate-limiting) that will keep the use cases intact.
We'd like to ship the API as callable multiple times, while continuing to discuss this point. This could unfold in several ways:
  • We might be able to convince Mozilla of the correctness of our viewpoint.
  • We might find out that legitimate websites often call setCaptureHandleConfig() multiple times (but not excessively), making it easier for us to convince Mozilla.
  • We might find out that websites rarely call setCaptureHandleConfig() multiple times, allowing us to rather painlessly change the function to being callable only once.
  • We might find out that some websites call setCaptureHandleConfig() multiple times in suspicious ways, in which case we'd change the function to being callable only once.
As part of the launch, we'll add usage metrics and keep close watch for the possibility of suspicious usage of the type Mozilla is worried about.
In either case, we have a reasonable way forward regardless of how things turn out.

WebKit:

Engaged in discussions in the W3C and approved the adoption of this document.

Web developers:
Strong positive signals from:
Other signals:
N/A

Debuggability

No DevTools support is needed.


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

No


Tracking bug

https://bugs.chromium.org/p/chromium/issues/detail?id=1200910

Launch bug

https://bugs.chromium.org/p/chromium/issues/detail?id=1200907

Sample links

https://w3c.github.io/mediacapture-handle/identity/demos/remote_control/capturer.html
https://w3c.github.io/mediacapture-handle//identity/demos/self_capture_detection/index.html

Estimated milestones

OriginTrial desktop last102
OriginTrial desktop first92

Link to entry on the Chrome Platform Status

https://chromestatus.com/feature/4854125411958784

Links to previous Intent discussions

Intent to prototype: https://groups.google.com/a/chromium.org/g/blink-dev/c/yLTykllpNmI
Intent to Experiment: https://groups.google.com/a/chromium.org/g/blink-dev/c/RKONugfoGwM/m/mpFizHPxAwAJ
Intent to Extend Experiment Again: https://groups.google.com/a/chromium.org/g/blink-dev/c/fB3IZDgcoco


This intent message was generated by Chrome Platform Status.

Yoav Weiss

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Mar 10, 2022, 2:01:59 AMMar 10
to Elad Alon, blink-dev
On Wed, Mar 9, 2022 at 11:26 AM 'Elad Alon' via blink-dev <blin...@chromium.org> wrote:

Contact emails

elad...@chromium.org

Explainer

https://github.com/w3c/mediacapture-handle/blob/main/identity/README.md

Specification

https://w3c.github.io/mediacapture-handle/identity/

Summary

We introduce a mechanism that allows an application to opt-in to exposing certain information to other applications which are video-capturing it. This allows collaboration between capturing and captured applications. For example, a VC application that's video-capturing a tab where a presentation application lives, could expose user-facing controls in the VC tab for navigating the presentation in the captured tab.


TAG review

https://github.com/w3ctag/design-reviews/issues/645

It seems worthwhile to give the TAG a few more weeks to get back to this, as they may be able to weigh in on some of the open issues.
 
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Elad Alon

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Mar 23, 2022, 8:26:02 AMMar 23
to blink-dev, yoav...@chromium.org, blink-dev, Elad Alon
TAG has just closed this issue as "satisfied" and posted "we are happy to see this move forward."

chrishtr via Chromestatus

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Mar 23, 2022, 11:27:06 AMMar 23
to blin...@chromium.org
LGTM1

Yoav Weiss

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Mar 23, 2022, 11:32:40 AMMar 23
to blink-dev, chrishtr via Chromestatus
LGTM2

On Wednesday, March 23, 2022 at 4:27:06 PM UTC+1 chrishtr via Chromestatus wrote:
LGTM1

mkwst via Chromestatus

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Mar 23, 2022, 11:34:24 AMMar 23
to blin...@chromium.org
LGTM3.

Elad Alon

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Mar 23, 2022, 11:48:45 AMMar 23
to blink-dev, mkwst via Chromestatus
Thank you all!
Sorry for not asking originally, but - may we ship gaplessly?

On Wednesday, March 23, 2022 at 4:34:24 PM UTC+1 mkwst via Chromestatus wrote:
LGTM3.

Yoav Weiss

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Mar 23, 2022, 11:57:59 AMMar 23
to Elad Alon, blink-dev, mkwst via Chromestatus
LGTM for a gapless OT

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