[wp-trac] [WordPress Trac] #32597: mediaelement.js high CPU usage in Firefox

[WordPress Trac]

#32597: mediaelement.js high CPU usage in Firefox
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 Reporter:  afercia             |       Owner:  (none)
     Type:  defect (bug)        |      Status:  new
 Priority:  normal              |   Milestone:  Awaiting Review
Component:  External Libraries  |     Version:
 Severity:  normal              |  Resolution:
 Keywords:                      |     Focuses:
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Changes (by afercia):

 * keywords:  close =>


Comment:

 > Leaving this open until someone that can reliably reproduce the issue

 There you go (see attached screenshot).

 Tested on a MacBook Pro end 2015 (not a brand new one but still powerful
 enough). Notes:
 - this now happens only with posts made with Classic Editor, as the block
 editor uses the native `<video>` element thus browsers use their own
 players
 - worth noting that these posts will use mediaelement.js also in the front
 end so the high CPU usage will happen also on the front end, which is
 unfortunate

 To reproduce:
 - use Classic Editor
 - add an audio
 - mediaelement.js will display its player
 - the easiest way to reproduce is by _not_ playing the audio and instead:
 - search in the browser's dev tools for an element with CSS class `mejs-
 time-buffereing`
 - make it visible by unchecking `display: none` (see screenshot)
 - the buffering CSS animation will appear
 - monitor the CPU usage with Activity Monitor (on macOS) or other tools if
 on Windows
 - in my case, testing with Chrome 85, the CPU usage goes up to 63%, which
 is crazy high

 This can be a huge problem when the network is unstable and buffering
 kicks in or when, as mentioned in the Slack conversation linked in the
 ticket description, a post is left open in a browser tab for some time.

 Worth also noting this ticket is 5 years old but it's still a problem for
 millions of posts published with previous versions of WordPress where the
 front end still uses mediaelement.js

-- 
Ticket URL: <https://core.trac.wordpress.org/ticket/32597#comment:8>
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