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Old 12-02-10, 12:15 PM   #1
damdim
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Default Backlight gets reseted with VDPAU

I have an issue with the brightness of my laptop (VAIO VPCCW1S1E with GT230M) and I want to track down the cause of it. I have installed nvidiabl and it works great. The problem is that If I don't use composite of the window manager, then when I try to play a video with VDPAU output then the backlight is reseted to its' maximum value. If I use a composition window manager with opengl rendering, then the backlight is reseted even when I run a 3D app f.e. glxgears. If I use Xrender instead of opengl, then the backlight is not reseted neither with VDPAU nor with 3D apps. This happens in GNOME and KDE and it doesn't happen in another laptop with Intel integrated graphics. Do you have an idea of what might causing this behavior?
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Old 12-02-10, 11:20 PM   #2
zchronos
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Default Re: Backlight gets reseted with VDPAU

Me too!

Card: GeForce GT220 (XFX - 1GB DDR2)
Nvidia Driver: NVIDIA-Linux-x86_64-260.19.21.run
S.O: openSUSE 11.3 (x86_64)
kernel: 2.6.34.7-0.5-desktop
D.E: KDE 4.5.3

VDPAU es awesome fast, but... la 260.19.21 have bugs with the colors (bright, constrast, ganma are reset).
Attached Files
File Type: gz nvidia-bug-report.log.gz (53.2 KB, 88 views)
File Type: log log_vdpau.log (17.6 KB, 91 views)
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Old 12-03-10, 11:41 AM   #3
Stephen Warren
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Default Re: Backlight gets reseted with VDPAU

Does this still happen without nvidiabl? I can't really find any information on nvidiabl, but I'd suggest contacting the maintainers of that application first, since you're explicitly controlling your backlight with it.
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Old 12-03-10, 12:02 PM   #4
damdim
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Default Re: Backlight gets reseted with VDPAU

It's a module I found in this forum.
http://www.nvnews.net/vbulletin/showthread.php?t=143025
Without it I cannot control backlight even with:
Code:
Option "RegistryDwords" "EnableBrightnessControl=1"
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Old 12-06-10, 08:42 AM   #5
alessandro_ufms
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Default Re: Backlight gets reseted with VDPAU

It's happens to me on fullscreen flash videos.
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Old 12-27-10, 06:02 PM   #6
xificurk
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Default Re: Backlight gets reseted with VDPAU

I have Dell Vostro 3700 (GeForce GT 330M), kernel 2.6.36 and nvidia-drivers 260.19.29 and have the same problem. I have found out that when the compositing in KDE4 is switched on/off, "something" (probably nvidia-driver) resets the brightness level of the display to the last value set by Fn keys, ignoring the current level.
I assume the switch of compositing is a trigger - I can see this happen also when e.g. going to fullscreen video playback or switching to VT (but only when compositing is enabled).
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Old 01-09-11, 09:08 AM   #7
guillaumezin
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Default Re: Backlight gets reseted with VDPAU

Quote:
Originally Posted by Stephen Warren View Post
Does this still happen without nvidiabl? I can't really find any information on nvidiabl, but I'd suggest contacting the maintainers of that application first, since you're explicitly controlling your backlight with it.
Hello,

I'm the maintainer of the nvidiabl module. Do you have any kind of information on the meaning of bit 30 and 31 of the brightness register (@c084)? As you can see here: http://www.nvnews.net/vbulletin/show...=1#post2374990 the register is restored by another module (I don't know wich one) with bit 30 set.

Thank you.

Best regards

Guillaume
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Old 01-10-11, 10:47 AM   #8
Stephen Warren
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Default Re: Backlight gets reseted with VDPAU

guillaumezin,

I'm sorry, but NVIDIA doesn't publish the programming information for our GPUs, so I can't provide that information.

Can you explain in more detail what nvidiabl does, and why it's needed, and how it interacts with VDPAU? Thanks.
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Old 01-10-11, 04:10 PM   #9
guillaumezin
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Default Re: Backlight gets reseted with VDPAU

Quote:
Originally Posted by Stephen Warren View Post
guillaumezin,

I'm sorry, but NVIDIA doesn't publish the programming information for our GPUs, so I can't provide that information.

Can you explain in more detail what nvidiabl does, and why it's needed, and how it interacts with VDPAU? Thanks.
Complete sources are here: https://github.com/guillaumezin/nvidiabl

nvidiabl doesn't interact at all with nvidia driver or VDPAU, it only plays with the brighness register (relative address 0xc084) - I got this register address from the nvclock project (http://www.linuxhardware.org/nvclock) and similar brightness drivers (http://wingolog.org/pub/nvbacklight-0.1.tar.bz2 and https://launchpad.net/~mactel-support-community)
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Old 01-10-11, 05:42 PM   #10
Stephen Warren
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Default Re: Backlight gets reseted with VDPAU

I guess this problem isn't surprising then; the nvidia kernel driver owns all GPU registers and has no provisions to share them. Hence, any changes made by nvidiabl can and will get over-written. I'd imagine this is happening with VDPAU in particular, because it programs various display registers to set up the overlay.

Why is nvidiabl needed; are there bugs in the nvidia driver that should be addressed instead?
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Old 01-11-11, 12:16 AM   #11
damdim
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Default Re: Backlight gets reseted with VDPAU

Quote:
Originally Posted by Stephen Warren View Post
Why is nvidiabl needed; are there bugs in the nvidia driver that should be addressed instead?
Because without nvidiabl we cannot control the backlight of various laptops based on nvidia GPUs.
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Old 01-11-11, 11:22 AM   #12
guillaumezin
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Default Re: Backlight gets reseted with VDPAU

Quote:
Originally Posted by damdim View Post
Because without nvidiabl we cannot control the backlight of various laptops based on nvidia GPUs.
+1

Playing with this register is today the only solution to control the backlight on every laptops equipped with modern nVidia GPU. And the nvidia driver doesn't handle at all the backlight, this is not a bug, this is more a missing feature, quite complicated to implement because values to be used in this register are dependant on laptop brand and model.

Guillaume
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