nv driver does not use correct color depth - gradient banding

[oss_test_launchpad]

Binary package hint: xserver-xorg-video-nv

On a MacBook Pro rev. 3 which uses an nVidia Corporation GeForce 8600M GT (rev a1) graphics, the default nv driver has problems displaying the right color depth. You can see that in the screenshot image attached.

Since the Nvidia driver does is not properly embedded into Ubuntu either at the moment, Ubuntu 8.10 seems to offer no way to be used with proper graphics on a MacBook Pro.

[Timo Aaltonen (tjaalton)]

I don't see anything wrong with the picture. Please attach your /var/log/Xorg.0.log.

[oss_test_launchpad (oss-test-launchpad)]

When you look closely you can see that there is no fluent transition from one color tone to another but steps. It is even far worse with the login screen but I wouldn't know how to make a screenshot of that.

Sorry I can't attach any logfiles that might help you. I just went back to the Nvidia driver.

[phenest (steve-clark)]

I've been thinking about this screenshot and realise why Timo can't see anything wrong. The png file will look correct under a 24 bit display, but have gradients under a 16 bit display.

[Bryce Harrington (bryce)]

Created an attachment (id=19860)
Xorg.0.log

Forwarding this bug from a Ubuntu reporter:
https://bugs.edge.launchpad.net/ubuntu/+source/xserver-xorg-video-nv/+bug/270455

[Original Report]
"On a MacBook Pro rev. 3 which uses an nVidia Corporation GeForce 8600M GT (rev a1) graphics, the default nv driver has problems displaying the right color depth. You can see that in the screenshot image attached.

When you look closely you can see that there is no fluent transition from one color tone to another but steps. The png file will look correct under a 24 bit display, but have gradients under a 16 bit display."

[Screenshot]
http://launchpadlibrarian.net/17618671/screenshot_nv_driver_desktop_background_color_depth_problem.png

[Aaron Plattner (aplattner)]

The nv driver currently does not detect the presence of 6-bit panels and won't enable dithering by default. Please try running

  xrandr --output LVDS --set dither 1

to see if it resolves the problem.

[Bryce Harrington (bryce)]

oss_test_launchpad, I've forwarded your bug upstream to https://bugs.freedesktop.org/show_bug.cgi?id=18215. Could you please subscribe to that bug, in case upstream wishes further information or needs you to test something? Thanks ahead of time!

[Bryce Harrington (bryce)]

Upstream says...

The nv driver currently does not detect the presence of 6-bit panels and won't
enable dithering by default. Please try running

  xrandr --output LVDS --set dither 1

to see if it resolves the problem.

oss_test_launchpad, please try this and report back on the upstream bug. Thanks.

[Aaron Plattner (aplattner)]

From the downstream bug:

oss_test_launchpad wrote:
> Sorry, but switching to the Nvidia driver was quite a hard thing due to
> the bug(s) surrounding its installation, so I wouldn't dare to change
> anything right now.

Closing, since the "dither" RandR property and the "FPDither" xorg.conf option are already available to control this.

[oss_test_launchpad (oss-test-launchpad)]

Sorry, but switching to the Nvidia driver was quite a hard thing due to the bug(s) surrounding its installation, so I wouldn't dare to change anything right now.

[Aaron Plattner (aplattner)]

Okay. I'm going to go ahead and close this (and the upstream bug), then. The "dither" RandR property or the "FPDither" xorg.conf option should do what you want. See the man page for details.

[Albert Einstein (spideryzarc)]

I have the same problem but only with compiz actived. I have a dell inspiron 9400. nvidia 7900 gs , drives v. 180
when I active the compiz the color depth seems to be changed down. xwininfo command return depth 24 wherever, but it is not what I see.

[Albert Einstein (spideryzarc)]

ok, back to the drivers 177 the problem disappeared.