Color banding

kwolf · 08-05-2012, 02:35 AM

I am getting a lot of banding (I think that's what to call it) on gradients on a product that uses displaylink for the screen (Yiynova DP10HD drawing tablet). The computer it's connected to is a windows 7 dual core, 4 gigs of ram, radeon 4670 - so its definitely not underpowered. I verified that the color depth is set to 32 bits on the PC and i tried both the v 6.3 and v 7 beta drivers but the issue is on both. A smooth black - white gradient does not appear not smooth at all like it does on the laptop LCD. This is one gradient I was using to test the display: http://www.lagom.nl/lcd-test/gradient.php It looks like the very last image on that site, except the gradient is divided into more "bars". If i manually set the display to 16 bit color, it's even worse.

Is there any way to fix this?

Wim · 08-05-2012, 10:40 AM

Can you tell me what DisplayLink hardware you are using?

Wim

kwolf · 08-05-2012, 02:43 PM

I'm not sure what chip they use in these, is there a way I can find out? This is the hardware ID string in my device manager:
USB\VID_17E9&PID_0252&REV_0144

The manufacturer says this is normal behavior and took a picture for me showing the same banding, so it could just be the nature of the DisplayLink compression. Here's a couple pictures to illustrate the difference between a normal display of a gradient and how it appears on my DisplayLink screen.

normal: http://i.imgur.com/X8POv.jpg
tablet: http://i.imgur.com/n3CL7.jpg

Wim · 08-05-2012, 07:32 PM

Thanks for the information. I think I can explain this.

This is due to the panel rather than the DisplayLink compression. I think the panel is 18bit, rather than 24 bit, so the lower bits of the pixel color is missing, which is why you see the banding.

We output 24 bit color, but the panel is losing the lower bits, which has been chosen by the manufacturer. Under normal use, you would never notice this difference, but color ramps will show it up.

Wim

kwolf · 08-05-2012, 08:00 PM

Thanks for the info, Wim! Much appreciated.

08-05-2012, 02:35 AM	#1
kwolf Junior Member Join Date: Aug 2012 Posts: 3	Color banding I am getting a lot of banding (I think that's what to call it) on gradients on a product that uses displaylink for the screen (Yiynova DP10HD drawing tablet). The computer it's connected to is a windows 7 dual core, 4 gigs of ram, radeon 4670 - so its definitely not underpowered. I verified that the color depth is set to 32 bits on the PC and i tried both the v 6.3 and v 7 beta drivers but the issue is on both. A smooth black - white gradient does not appear not smooth at all like it does on the laptop LCD. This is one gradient I was using to test the display: http://www.lagom.nl/lcd-test/gradient.php It looks like the very last image on that site, except the gradient is divided into more "bars". If i manually set the display to 16 bit color, it's even worse. Is there any way to fix this?

08-05-2012, 02:43 PM	#3
kwolf Junior Member Join Date: Aug 2012 Posts: 3	I'm not sure what chip they use in these, is there a way I can find out? This is the hardware ID string in my device manager: USB\VID_17E9&PID_0252&REV_0144 The manufacturer says this is normal behavior and took a picture for me showing the same banding, so it could just be the nature of the DisplayLink compression. Here's a couple pictures to illustrate the difference between a normal display of a gradient and how it appears on my DisplayLink screen. normal: http://i.imgur.com/X8POv.jpg tablet: http://i.imgur.com/n3CL7.jpg Last edited by kwolf; 08-05-2012 at 04:41 PM.

08-05-2012, 10:40 AM	#2
Wim Senior Member Join Date: Feb 2009 Posts: 1,561	Can you tell me what DisplayLink hardware you are using? Wim

08-05-2012, 07:32 PM	#4
Wim Senior Member Join Date: Feb 2009 Posts: 1,561	Thanks for the information. I think I can explain this. This is due to the panel rather than the DisplayLink compression. I think the panel is 18bit, rather than 24 bit, so the lower bits of the pixel color is missing, which is why you see the banding. We output 24 bit color, but the panel is losing the lower bits, which has been chosen by the manufacturer. Under normal use, you would never notice this difference, but color ramps will show it up. Wim

08-05-2012, 08:00 PM	#5
kwolf Junior Member Join Date: Aug 2012 Posts: 3	Thanks for the info, Wim! Much appreciated.