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dividuum
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Lost video signal on screenshot capture @4K

Tue Oct 01, 2019 3:42 pm

Hey. For my service, I capture snapshots on what's currently on the screen using my pretty basic dispmanx->jpeg snapshot tool from https://github.com/info-beamer/tools/tr ... screenshot

This worked pretty well so far, but with [email protected] output and especially now with rendering 4K videos as well, the HVS seems to be overloaded when using this approach and snapshotting results in a temporary loss of the HDMI signal.

In theory, I guess I might copy the generated GL buffer from DRM and awkwardly reassemble what's on the screen on my own by then also trying to grab all the video layers from ` vc.ril.video_render` somehow. But that sounds like a complexity nightmare just to get a screen snapshot.

I wonder if there's any other way I might not be aware of, other than maybe using dispmanx_offline=1 and slowing down everything as a side effect.
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jamesh
Raspberry Pi Engineer & Forum Moderator
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Re: Lost video signal on screenshot capture @4K

Tue Oct 01, 2019 3:49 pm

Sounds like your analysis might well be rigth - you are effectively try to do 2 4kp60 renders which overloads the system (the reason why we don't support 2 x 4kp60 displays, and limited to p30) . Have you tried overclocking the videocore? Should be able to get to 600. I think its 500 by default.
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dividuum
Posts: 181
Joined: Sun Jun 16, 2013 1:18 pm
Location: Germany
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Re: Lost video signal on screenshot capture @4K

Tue Oct 01, 2019 4:26 pm

jamesh wrote:
Tue Oct 01, 2019 3:49 pm
Sounds like your analysis might well be rigth - you are effectively try to do 2 4kp60 renders which overloads the system (the reason why we don't support 2 x 4kp60 displays, and limited to p30) . Have you tried overclocking the videocore? Should be able to get to 600. I think its 500 by default.
Thanks for the quick response. I'd rather not use workarounds that might result in a potentially unstable system. I guess I'll have to see how I'll handle this then.
info-beamer hosted - A user and programmer friendly digital signage platform for the Pi: https://info-beamer.com/hosted

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