1541471 - (me-capture-stream) [meta] Implement spec-compliant `HTMLMediaElement`.captureStream

Status: NEW

(Core :: Audio/Video: MediaStreamGraph, enhancement, P3)

Description

[Paul Adenot (:padenot)]

We have old and incorrect (per-spec) mozCaptureStream and mozCaptureStreamUntilEnded, that we should adjust and rename to be spec-compliant.

Comment 2

[Jan-Ivar Bruaroey [:jib] (needinfo? me)]

Fixing title because captureStreamUntilEnded was removed from the spec, since it is trivial to emulate with

video.onended = () => track.stop();

Comment 3

[Andreas Pehrson [:pehrsons]]

(In reply to Jan-Ivar Bruaroey [:jib] (needinfo? me) from comment #2)

Fixing title because captureStreamUntilEnded was removed from the spec, since it is trivial to emulate with

video.onended = () => track.stop();

Well, if the video element ended, there wouldn't be any live track left to stop. If you wanted to cancel the capturing you could probably do something with GC of the MediaStream that was returned from captureStream.

I think the safest way to emulate captureStreamUntilEnded would be to stop using the captured media element and replace it with a pristine one.

Comment 6

[Byoungchan Lee]

Even in some code of webgpu tests check if HTMLMediaElement.captureStream is implemented or not.

https://searchfox.org/mozilla-central/source/testing/web-platform/mozilla/tests/webgpu/webgpu/web_platform/util.js#463
https://github.com/gpuweb/cts/blob/b0f5b1839f40f8f793ec2e4a6eecae41a273e0b3/src/webgpu/web_platform/util.ts#L463

Comment 7

[Jim Mathies [:jimm]]

NI over to Alastor who has agreed to pick this work up.

Comment 8

[Alastor Wu [:alwu]]

I’ll update my plan once I finish the investigation on this topic, keep my NI.

Comment 9

[Alastor Wu [:alwu]]

I’m going to make this bug a meta bug. Currently, implementation notes for mozCaptureStream()` on MDN are incorrect, and those issues have now been fixed. The major noncompliance issue is that Firefox does not keep audio playout active while the stream is being captured.

I will first file bugs to address this issue, while keeping mozCaptureStreamXXX() unchanged to avoid breaking existing sites. After that, I’ll add a new implementation for captureStream() along with proper test coverage.