DP/HDMI cable creating bad image

[5883662]

Hi guys,

I have a 5.1 Mac Pro with RX580 connected to a Acer B276HUL display via DVI cable and all was fine. I had to move the Mac Pro further away and needed a longer cable to connect it back up but didn't have a long enough DVI cable.

So I tried an HDMI and DP cable and both of them created a very bad image. Specifically the text and icons look over sharpened and perhaps didn't have any AA applied to them?

What I have tried:

• enabled/disabled font smoothing
• tried to manually set font smoothing
• checked display settings
• reset display to factory settings

Both HDMI and DP cable produce a normal image under Windows 10/BootCamp!

I'm absolutely baffled by this. Anyone have any tips?

 

[5883662]

Ok, so I found something else out:

When manually enabling and selecting HiDPI mode under display settings, all icons ante text is now back to "normal" eg. high resolution, looks great. Obviously everything is at much larger scale, so it's not usable.

But it does proof that the problem lies in Mac OS not "loading" proper assets for the display? I don't know why it does when using a DVI cable but not when using an HDMI or DP cable.

Has no one else got any ideas at all?

 

[h9826790]

Can't see anything wrong with your screen capture.

If that's cabling issue, screen capture will not able to show the problem, because that's capturing the rendered image from the RAM.

Anyway, if HiDPI work, you may use "super resolution" (e.g. 2560x1440 HiDPI) for your computer.

I did that as well. Not because of having issue, but better font (AA), and better screen capture.

My monitor's native resolution is 3840x1080

But I let the RX580 render at 7680x2160 (3840x1080 HiDPI)

You may see if ResXtreme allow you to do that.

http://resxtreme.com/

After you open the apps and select your monitor, click "scale", and all the x2 scale are the HiDPI options.

Anyway, here is comparison between HiDPI and non-HiDPI rendering. As you can see, HiDPI so so much better. The non-HiDPI font smoothing makes the text looks really bad.

 

[5883662]

Can't see anything wrong with your screen capture.

If that's cabling issue, screen capture will not able to show the problem, because that's capturing the rendered image from the RAM.

Anyway, if HiDPI work, you may use "super resolution" (e.g. 2560x1440 HiDPI) for your computer.

I did that as well. Not because of having issue, but better font (AA), and better screen capture.

My monitor's native resolution is 3840x1080
View attachment 831842

But I let the RX580 render at 7680x2160 (3840x1080 HiDPI) View attachment 831843

You may see if ResXtreme allow you to do that.

http://resxtreme.com/

After you open the apps and select your monitor, click "scale", and all the x2 scale are the HiDPI options.
View attachment 831846

Anyway, here is comparison between HiDPI and non-HiDPI rendering. As you can see, HiDPI so so much better. The non-HiDPI font smoothing makes the text looks really bad.
View attachment 831844

Thanks for your help. I have downloaded the app and tried the HiDPI resolutions. It does look better but now everything is huge!

 

[h9826790]

Thanks for your help. I have downloaded the app and tried the HiDPI resolutions. It does look better but now everything is huge!

View attachment 832213 View attachment 832214

So, 2560x1440 HiDPI does not available, but only 1280x720 HiDPI?

 

[5883662]

So, 2560x1440 HiDPI does not available, but only 1280x720 HiDPI?

Correct!

 

[h9826790]

Correct!

Then you may really need SwitchResX

 

[5883662]

That is not available either in SwitchResX

 

[h9826790]

That is not available either in SwitchResX

Custom resolution in SwitchResX?

 

[5883662]

I don't understand how to save them?
[doublepost=1555324150][/doublepost]Managed to save the custom resolution but now get a black screen after login and I can’t see anything. I’ve booted into recovery mode and manually removed the app and pref pane but the resolution seems to stick around. Any ideas?

This is going from bad to worse lol!

 

[5883662]

Managed to restore a local snapshot from earlier this morning.

 

[h9826790]

I don't understand how to save them? View attachment 832223
[doublepost=1555324150][/doublepost]Managed to save the custom resolution but now get a black screen after login and I can’t see anything. I’ve booted into recovery mode and manually removed the app and pref pane but the resolution seems to stick around. Any ideas?

This is going from bad to worse lol!

Remove the DP cable, and plugin the HDMI cable should go back to native resolution automatically

 

[5883662]

Thanks - I tried that and many other things before I restored local time machine snapshot.

 

[krakman]

hi i think you need to force RGB mode.

The clue is in the monitor resolutions window..... you are showing 1080p and 1080i these are TV resolutions because your mac thinks the monitor is a TV and is probably outputting YCbCr instead of RGB.

the solution is here: https://www.mathewinkson.com/2013/0...ix-the-picture-quality-of-an-external-monitor

I had the same issue after running the rgb override the GUI loks good and 1080p & 1080i resolutions disappear from the bottom of the list.

 

[h9826790]

hi i think you need to force RGB mode.

The clue is in the monitor resolutions window..... you are showing 1080p and 1080i these are TV resolutions because your mac thinks the monitor is a TV and is probably outputting YCbCr instead of RGB.

the solution is here: https://www.mathewinkson.com/2013/0...ix-the-picture-quality-of-an-external-monitor

I had the same issue after running the rgb override the GUI loks good and 1080p & 1080i resolutions disappear from the bottom of the list.

View attachment 832253

That may help in some case, but I don't think it's "TV" related.

My setup also has 1080P and 1080i option. And from post #3 screen captures, you can see that my setup shows "Television: Yes", but still using RGB 30bit output.

 

[5883662]

That may help in some case, but I don't think it's "TV" related.

My setup also has 1080P and 1080i option. And from post #3 screen captures, you can see that my setup shows "Television: Yes", but still using RGB 30bit output.

OMG you are a god damn legend! That did the trick. Thank you so much for everyone's help!

 

[krakman]

That may help in some case, but I don't think it's "TV" related.

My setup also has 1080P and 1080i option. And from post #3 screen captures, you can see that my setup shows "Television: Yes", but still using RGB 30bit output.

Yes its a bit of a conundrum!

When I used a pair of 27 inch 1920x1080 monitors I didn't experience any issues. but as soon as I upgraded to higher res monitors on my system I began to notice the over sharpened text as mentioned by the OP.

There are a lot of people complaining about various monitor issues on the blog post that i linked to. It seems to have started a few years ago with Mavericks.

The screen shot below shows my current set up, the 32 inch screens needed the RGB override but the 34 inch ultra wide shows the 1080p/i resolutions but the display is crisp and clear, perhaps because I have it in HDPI mode?

In the office we have another 3 mac pros with various monitors ( generally 32 inch AOC) and I have applied the RGB fix to all of them - I think.

IF i get time i will investigate to see if i can find a pattern to this behaviour.

 

[5883662]

I did think it was strange that the display works fine with a DVI cable but goes bad when using HDMI and DP cable. Together with the fact that under Windows, it all looks fine regardless of which cable/port I use clearly indicates that this is a software bug with OS X.

 

[krakman]

I did think it was strange that the display works fine with a DVI cable but goes bad when using HDMI and DP cable. Together with the fact that under Windows, it all looks fine regardless of which cable/port I use clearly indicates that this is a software bug with OS X.

Yes it think you are right!!!!

I used mDP to DVI cables with my 1920x1080 monitors and all was good. Upgrading to 32 and 34 inch monitors required use of DP/HDMI cables and thats when the issue appeared.

My upgrading of monitors coincided with Mavericks so the bug/issue may have been present in older versions of OSX ???

The first time I experienced it was with a 2 monitor setup. One monitor was HD, the second was a 21:9 2560x1080 connected by DP

My hypothesis:

Monitor with >HD resolution + DP/HDMI cable = MAC OS outputs YCbCr instead of RGB

But there is evidence that this issue does not occur with all monitors, only some brands/models of monitor.

Also my wife had the issue on her monitor but she did not notice it until I pointed it, so I wonder if many people are simply not noticing the issue??

 

[5883662]

Let's hope search engines will pick this up and get people to resolve their issue if they have the same one.

 

[5883662]

OMG you are a god damn legend! That did the trick. Thank you so much for everyone's help!

Just a heads up with Mac OS Catalina: Disabling SIP is no longer the only step as you will have to mount your / read-write, which is off by default. To do this type: sudo mount -uw / followed by your password. You will then have to copy the directory/files created with the script in the shell/zsh as well.

 

[MacPoulet]

Hi all, I think I'm having the same issue. I have a Dell U2413 display (1920 x 1200) and it looks great with DVI. I added a second monitor which only takes DVI and plugged the U2413 in with HDMI and it looks terrible, same as how earlier posts describe the image. Is this fix still valid? I'm currently running Mojave on my Mac Pro and I'm a little weary to modify the system as my Mac Pro has gone from being a secondary support machine to a primary during covid.

Would an HDMI to DVI cable for the old monitor be a less risky fix as its resolution is less than 1920 x 1080?