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Video clip in 4:2:2 chroma subsampling fails to play in Chrome
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Description

There is an example on the page w:no:User:Jeblad/Example Myrdal station of a rather huge video with a deep link nearly two hours into the movie. This movie loads and autostarts as it should in a Firefox browser on Win10, it loads but does not autostarts on Ubu18.04. Not autostarting on Ubu is probably because I have turned off autostart in the config.

All other webkit-based browsers I have tested on both OS' have failed. Edge on Win10 works, but with artifacts.

Inspecting the console in Chromium on Ubu, it says

Uncaught (in promise) DOMException: The play() request was interrupted by a call to pause(). https://goo.gl/LdLk22

The same uncaught exception is not reported in Firefox.

So, in short, seems like a bug…

The console is appended as

Event Timeline

jeblad renamed this task from Large (huge) movie clip does not play in webkit browsers (uncaught exception) to Large (huge) movie clip does not play in webkit browsers (bug – uncaught exception).Oct 1 2018, 3:16 AM

Looks like a bug with the old mwembed player assuming it can autoplay and interacting badly with current browsers...

I did some more poking at this, and I'm not quite sure what's going on but I don't think it's because of the pause/play stuff.

Chrome won't play the file at all -- it comes up but always shows a black screen and never progresses.

Aha found it -- the file is 4:2:2 chroma subsampling (profile 1) which Chrome probably doesn't support.

I'll have to force our transcodes to use 4:2:0 subsampling with is more widely supported.

brooke renamed this task from Large (huge) movie clip does not play in webkit browsers (bug – uncaught exception) to Video clip in 4:2:2 chroma subsampling fails to play in Chrome.Oct 1 2018, 6:17 PM
brooke edited projects, added TimedMediaHandler-Transcode; removed Kaltura player.

Note that MS Edge messes up the color.
Good catch btw!

(OMG! He was to smart! I could not confuse him! Argh!)

Change 463841 had a related patch set uploaded (by Brion VIBBER; owner: Brion VIBBER):
[mediawiki/extensions/TimedMediaHandler@master] Force Web output to 4:2:0 subsampling for Chrome, Edge compat

https://gerrit.wikimedia.org/r/463841

Change 463841 merged by jenkins-bot:
[mediawiki/extensions/TimedMediaHandler@master] Force WebM output to 4:2:0 subsampling for Chrome, Edge compat

https://gerrit.wikimedia.org/r/463841

Will this fix be available soonish or do we wait for the ordinary rollout?

I'll try to sneak it into a 'swat deploy' window later this week.

@jeblad, I did reset the transcodings. Can you please check the video again?

brooke claimed this task.

I didn't manage to do an early push because I was out sick most of last week, but it should be live now, and the re-rendered file works for me so hoping it's fine for @jeblad. :)

I'm going to go ahead and mark this resolved; if any problems please reopen.

The fix seems to work for the rerendered file.
:)