How to Debug Video Mode not Supported (lemmy.ml)

submitted 1 month ago by etbe@lemmy.ml to c/linux@lemmy.ml

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I previously posted to Lemmy about my 8K TV and attempts to get it working on Linux. Based on suggestions there I bought an Intel Arc B580 which apparently supports 8K. But I can't get that on my TV. I've tried multiple cables, multiple video cards (including the NVidia one), and both HDMI and DisplayPort output from GPUs.

How can I find out where the problem is? Can I interrogate a HDMI or DisplayPort target to find out what modes it claims to support? Can I ask the GPU what modes are actually supported on it's outputs? If so how?

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[-] Oinks@lemmy.blahaj.zone 1 points 1 month ago* (last edited 1 month ago)

I don't have deep knowledge on the topic but you might want to look into EDID, which is how your system knows what resolutions the monitor supports. Incorrect detection of maximum resolutions and refresh rates is a semi-common problem on Linux and the fix for that is a custom modeline; setting one will be compositor dependent on Wayland (on X11 xrandr will do).

However it's also possible that all the cables you have are bad and/or don't support 8K.

[-] etbe@lemmy.ml 2 points 1 month ago

Thanks for the advice, I installed the Debian package "read-edid" and used the get-edid program from it to get the EDID from the monitor. Then I installed the "wxedid" package to display it graphically because the parse-edid program from read-edid didn't work well. According to wxedid there's a seletion of 38402160 modes and some 40962160 modes. So it seems that the EDID is the problem.

this post was submitted on 06 Nov 2025

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