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[tjobbins]

Version: 28.0.72
OS: Big Sur 11.5.2
Video Renderer: JRVR + "Hardware accelerate video decoding when possible"
Tree & View: Full Screen -> Monitor -> Display #3
System: Mac Pro 2019 with four monitors (1 x 3840x2160, 3 x 1920x1200)
GPU: AMD 6900XT 16GB

I have macOS set to "Displays have separate Spaces", so I can switch spaces per-monitor.

When MC 28 is in Theater View Display Mode and a video is paused, if I switch the monitor that MC is on to a different Space - eg by using Mission Control or a trackpad gesture to switch to a Full Screen app on the same monitor - MC suddenly starts causing massive GPU usage:


Switching back to the Desktop with MC on causes the GPU usage to stop immediately.

The problem does not happen if the MC video is playing when the Space switch is done.  It only happens when the video is paused.

The problem does not happen if I switch Video Renderer to "Legacy OpenGL".

Attached is an Activity Monitor "Sample Process" log taken of MC while it's causing this high GPU usage.  Hopefully this is helpful for debugging the problem.

[JimH]

Theater View uses 3D drawing.  In Theater View settings, you can use a less demanding setting.

[tjobbins]

No, it's a bug.  The GPU usage rockets only when the Space is changed when a video is paused.  It goes from 0% to 50% by changing space *away* from MC.   Having a video playing on an active space shows little to no GPU usage.

[tjobbins]

This is GPU usage when MC is on a visible space and a video is playing in Theater View Display View - 0.6%:


It rockets to 50% - so much that I can hear the GPU fans spin up hard - if and only if I a) pause the video, and b) change Space away from MC.

[Hendrik]

Sounds like Mac forgets that VSYNC is a thing when the window is being hidden that way, so it could render without any speed limit. But i've just put a limit in for paused rendering so its not running away anymore.

[tjobbins]

Sounds like Mac forgets that VSYNC is a thing when the window is being hidden that way, so it could render without any speed limit. But i've just put a limit in for paused rendering so its not running away anymore.

Thank you, Hendrik.  It's not a problem I've ever had with any other program - I regularly use GPU-using apps in Full Screen windows and move between spaces all the time - so maybe they all need this workaround. Although now I think of it, pretty much all the others use Metal these days, so I couldn't say for sure regarding OpenGL stuff.

Anyway I'll try the next release and hopefully that'll sort it.  Thanks for the fast fix.

[tjobbins]

I just upgraded to 28.0.79 and the problem is gone.  Thanks very much, Hendrik.