Bug 278507 – Animated WEBP plays much slower than in other browsers

• Component: Images
• Status: RESOLVED MOVED

[Cat Ball]

Created attachment 472260 [details]
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

[Alexey Proskuryakov]

Thank you for the report! I can reproduce this on an M3 Mac with macOS 15 beta.

[Radar WebKit Bug Importer]

<rdar://problem/134535157>

[Said Abou-Hallawa]

This is an issue below WebKit, tracked by Apple internally as rdar://134535157.