[Webkit-unassigned] [Bug 278507] New: Animated WEBP has very slow framerate

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=278507

            Bug ID: 278507
           Summary: Animated WEBP has very slow framerate
           Product: WebKit
           Version: Safari Technology Preview
          Hardware: All
                OS: All
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Images
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: bugswebkit at catball.dev
                CC: sabouhallawa at apple.com

Created attachment 472260

  --> https://bugs.webkit.org/attachment.cgi?id=472260&action=review

Tarball containing webpage demo of the above bug. See also the github link in the bug for the same files.

Webkit seems to animate WEBP at a much slower framerate than is encoded in the image. This doesn't occur with the same image in Chrome or Firefox.


Here is a quick demo of the bug, comparing the same video file encoded as a 24 FPS gif and as a 24 FPS webp:

- https://catball.dev/bug_reports/animated_webp_bug/25_seconds.html
- https://github.com/catleeball/animated_webp_bug_demo

Notably, when 25 seconds on the timer in the gif have elapsed, the webp has only made it to approx 9 seconds. The first few frames appear to be more performant, then the animation slows considerably.


Tested on:

- MacOS 14.6.1
  - Safari 17.6
  - Safari Technology Preview 18.0
- iOS 17.6.1


Please let me know if you need any additional details. Thank you!
Cat

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