Hi folks,
I've recently acquired a new monitor and am trying to connect it to my laptop. I'm using a USB-C to HDMI adapter. The problem is that, when normal booting, the colors on the external monitor are really off. I mean like psychedelic-looking off. But my laptop screen colors are entirely normal. When viewing a color chart on the external monitor, its as if all the colors are shifted by some amount. I have also tested this same hardware setup using Windows 10 (dual-booted laptop), and there are absolutely no problems on Windows.
When I boot using safe mode, the problem goes away. However, of course this is due to not all the graphics drivers loading up by booting this way.
EDIT #1: I have tested using a different monitor. However, since the monitor doesn't have an HDMI port, I used an HDMI to DVI-D cable along with the HDMI to USB-C adapter. IT WORKS!!! And not just on the first time, but even after unplugging and replugging the cable multiple times and rebooting multiple times. But why? What's different between these two monitors that Kubuntu doesn't like, and can we make Kubuntu like it?
However, I also just tried it on a 4K TV with an HDMI 2.0 cable and it did not work.
I would really rather not have to return this new monitor just because it doesn't work in Kubuntu, so I'm really curious if a key difference between the two monitors can be pinpointed to get Kubuntu to work more consistently. Any suggestions on what I should dig further into?
EDIT #2: I've pinpointed exactly how the color space appears to be transformed on the weird external monitor output. First, I went to https://www.w3schools.com/colors/colors_picker.asp and scrolled down to the RGB picker. What I found is that the monitor is outputting each R, G and B value modulus 19. So for example, setting G and B to 0, R is black at 0 and increases in redness up to 18. Then, at 19, it immediately drops back to full black and the cycle repeats, increasing from 19 to 37 and then dropping back to full black, etc.. Same happens for green and blue channels, holding all other channels at 0. In fact, I've verified that it compress the entire 0 to 255 range into 0 to 18 intervals.
EDIT #3: I've found a more manageable workaround where I noticed that if I let the monitor go completely into power saving mode on its own by unplugging the HDMI cable and waiting a bit until the screen is fully dark, and then plug the cable back in, then normal colors appear on the screen (most of the time, maybe about 5% of the time this doesn't work but this technique has been the most consistent). So maybe this isn't a boot-related issue, but something with the Intel HD drivers? Why does it produce correct colors only when the cable is plugged in after the monitor is completely in power saving mode?
Any ideas on how to resolve this issue, or what to look into further? Thanks!
I've recently acquired a new monitor and am trying to connect it to my laptop. I'm using a USB-C to HDMI adapter. The problem is that, when normal booting, the colors on the external monitor are really off. I mean like psychedelic-looking off. But my laptop screen colors are entirely normal. When viewing a color chart on the external monitor, its as if all the colors are shifted by some amount. I have also tested this same hardware setup using Windows 10 (dual-booted laptop), and there are absolutely no problems on Windows.
When I boot using safe mode, the problem goes away. However, of course this is due to not all the graphics drivers loading up by booting this way.
EDIT #1: I have tested using a different monitor. However, since the monitor doesn't have an HDMI port, I used an HDMI to DVI-D cable along with the HDMI to USB-C adapter. IT WORKS!!! And not just on the first time, but even after unplugging and replugging the cable multiple times and rebooting multiple times. But why? What's different between these two monitors that Kubuntu doesn't like, and can we make Kubuntu like it?
However, I also just tried it on a 4K TV with an HDMI 2.0 cable and it did not work.
I would really rather not have to return this new monitor just because it doesn't work in Kubuntu, so I'm really curious if a key difference between the two monitors can be pinpointed to get Kubuntu to work more consistently. Any suggestions on what I should dig further into?
EDIT #2: I've pinpointed exactly how the color space appears to be transformed on the weird external monitor output. First, I went to https://www.w3schools.com/colors/colors_picker.asp and scrolled down to the RGB picker. What I found is that the monitor is outputting each R, G and B value modulus 19. So for example, setting G and B to 0, R is black at 0 and increases in redness up to 18. Then, at 19, it immediately drops back to full black and the cycle repeats, increasing from 19 to 37 and then dropping back to full black, etc.. Same happens for green and blue channels, holding all other channels at 0. In fact, I've verified that it compress the entire 0 to 255 range into 0 to 18 intervals.
EDIT #3: I've found a more manageable workaround where I noticed that if I let the monitor go completely into power saving mode on its own by unplugging the HDMI cable and waiting a bit until the screen is fully dark, and then plug the cable back in, then normal colors appear on the screen (most of the time, maybe about 5% of the time this doesn't work but this technique has been the most consistent). So maybe this isn't a boot-related issue, but something with the Intel HD drivers? Why does it produce correct colors only when the cable is plugged in after the monitor is completely in power saving mode?
Any ideas on how to resolve this issue, or what to look into further? Thanks!
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