[Webkit-unassigned] [Bug 224161] New: Broken transition when video player with MediaStream changes size

bugzilla-daemon at webkit.org bugzilla-daemon at webkit.org
Sat Apr 3 14:46:03 PDT 2021


https://bugs.webkit.org/show_bug.cgi?id=224161

            Bug ID: 224161
           Summary: Broken transition when video player with MediaStream
                    changes size
           Product: WebKit
           Version: Safari 14
          Hardware: Mac (Intel)
                OS: macOS 10.15
            Status: NEW
          Severity: Critical
          Priority: P2
         Component: Animations
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: webkit-bugzilla at lavrins.com
                CC: dino at apple.com, graouts at apple.com

Reproduction:

1. Create video player element
2. Assign CSS transition to that element
2. Assign captured user media stream to that element
3. Change width and height of the element

What happens:

Video transitions are not smooth. Video mid-transition appears to be jerky, and sometimes black background being exposed.


What expected:

The transition should be smooth.



Additional info:


This demo reproduces this bug in Safari 14 on macOS

https://jsfiddle.net/ArmorDarks/enrL02yx/35/

1. Load the demo
2. Wait for predefined video to load
3. Click a few times the "Toggle video size" button - video will smoothly resize without any issues
4. Click "Start camera stream". It will request you camera stream and assign it to the same video player
5. Try the "Toggle video size" button again - instead of a smooth transition, the video will "jump" mid-transition and expose black background sometimes

Here's the recording of the reproduction:
https://www.dropbox.com/s/kcbse6bv18ri1og/Screen%20Recording%202021-04-04%20at%2000.36.15.mov?dl=0

It seems to be more prominent in heavier applications. For instance, this recording uses exactly the same positioning, but produces a much worse transition:
https://www.dropbox.com/s/mjgqzd4al175f8r/Screen%20Recording%202021-04-04%20at%2000.37.44.mov?dl=0

This case is quite common for modern web-based streaming solutions, like Restream Studio, which are using transitions on video element with a user's captured video to smoothly switch between different layouts. There seems to be no way to workaround that issue.

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