Steps to reproduce
- Visit https://commons.wikimedia.org/wiki/File:Wikidata%27s_World.webm (or any other video on commons.wikimedia.org) in Edge 14.
- Play the video. You can see that the video is playing very smoothly (assuming your network speed is fast).
- While the video is playing, right click on the video, and then click "Inspect element". When the F12 Tools window is open, you can see that the playing becomes slow and choppy. Then close F12 Tools, it plays smoothly again.
- Repeat steps 1-3 in Firefox and Chrome. In these two browsers, the video plays smoothly when F12 is open.
(1) This is reproducible only when playing videos on Wikipedia websites. Not reproducible on YouTube videos.
(2) Reproducible on both Edge 14.14393.51 x64 and Edge 14.14901 x64.
Comments and activity
The cause of this seems to be that video decoding is done using an asm.js module. Since asm.js is disabled in Edge when F12 is open, the decoding becomes slow. Although it would sometimes be handy for this not to be the case, this is apparently by design and probably won’t be fixed.
In Chrome/FF, the page instead displays a native video element (which doesn’t use the asm.js module) as a result of feature detection since those browsers support native VP8/Vorbis playback while Edge currently does not.
Thanks for your reply, Ryan! But I don’t think it is caused by asm.js being disabled, because the issue is exactly the same in IE 11 on Windows 10 (slow when F12 is open; fast when F12 is closed), and IE 11 doesn’t support asm.js at all.
- Microsoft Edge Team
Changed Assigned To to “Ibrahim O.”
Changed Assigned To to “Venkat K.”
Changed Status to “By design”
All the best,
The MS Edge Team
I see. Thank you for your explanation!