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Old 03-08-09, 02:47 PM   #1
QBert69
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Default Gamma and brightness settings not working when using VDPAU

Is there a way to change the gamma or brightness settings when using vdpau ?
If I change the values with the nvidia-settings tool this seems to work only if i use xv as videooutput. I have a 8400GS, the 180.35 driver and mplayer.

Thank you
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Old 03-08-09, 03:03 PM   #2
ReimarD
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Default Re: Gamma and brightness settings not working when using VDPAU

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Originally Posted by QBert69 View Post
Is there a way to change the gamma or brightness settings when using vdpau ?
The MPlayer controls (keys 3, 4) work for brightness. No idea about gamma, VDPAU does not seem to offer a function for that.
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Old 03-08-09, 08:22 PM   #3
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Default Re: Gamma and brightness settings not working when using VDPAU

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Originally Posted by QBert69 View Post
Is there a way to change the gamma or brightness settings when using vdpau ?
If I change the values with the nvidia-settings tool this seems to work only if i use xv as videooutput. I have a 8400GS, the 180.35 driver and mplayer.
MythTV's VDPAU output also ignores gamma set in nvidia-settings, unlike its Xv and OpenGL output. I suppose it's some fundament limit of the driver.
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Old 03-09-09, 01:23 AM   #4
Stephen Warren
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Default Re: Gamma and brightness settings not working when using VDPAU

Yes, there's no gamma setting in VDPAU. All other procamp manipulations should be made by the application, using the color space conversion matrix passed into the video mixer.

This provides applications with much better control over procamp than a simple system-wide setting.
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Old 03-24-10, 11:33 AM   #5
Muse ESUm
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Question Re: Gamma and brightness settings not working when using VDPAU

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Originally Posted by Stephen Warren View Post
Yes, there's no gamma setting in VDPAU. All other procamp manipulations should be made by the application, using the color space conversion matrix passed into the video mixer.

This provides applications with much better control over procamp than a simple system-wide setting.
Thanks for your explanation. I am trying to implement Gamma correction for vdr-sxfe, and I did not totally understand your remark. It suggests that one can achieve Gamma correction by passing a correct CSC matrix to VDPAU. However, Gamma correction is inherently nonlinear, so how does a *matrix* help here? Do I have to implement Gamma in software, i.e. using the xine software equalizer (eq2)?

Thanks in advance!

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Old 03-24-10, 11:43 AM   #6
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Default Re: Gamma and brightness settings not working when using VDPAU

Muse, I said "all *other* procamp settings" should use the CSC matrix. In particular, you mentioned brightness. There is indeed no way to manipulate gamma using VDPAU.
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Old 03-24-10, 12:17 PM   #7
Muse ESUm
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Default Re: Gamma and brightness settings not working when using VDPAU

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Originally Posted by Stephen Warren View Post
Muse, I said "all *other* procamp settings" should use the CSC matrix. In particular, you mentioned brightness. There is indeed no way to manipulate gamma using VDPAU.
OK, thanks and sorry for the misunderstanding - I am not a native speaker, and not a particularly attentive reader . I wonder whether anybody out there knows how to apply gamma correction to libxine with vdpau video output. I am using Ubuntu Karmic + the-vdr-team's libxine 1.2.0 with its included vdpau patch. I passed vdr-sxfe --post eq2:gamma=2.0 for testing purposes, and it doesn't seem to change any of the vdpau output. However, when closing the xine display window one can briefly see the last frame getting totally bright (as expected with a gamma correction of 2.0). I suppose vdpau employs some hardware overlay which bypasses of the software equalizer.

How can I influence the gamma of vdpau output at all? Maybe there is any possibility to make the vdpau overlay window respect the "xgamma" setting, which is also ignored ATM?
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Old 03-24-10, 12:29 PM   #8
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Default Re: Gamma and brightness settings not working when using VDPAU

Maybe it's some kind of libxine issue, since "mplayer -vf eq2=2.0 <somefile>" with a vdpau-patched mplayer outputs the file correctly, i.e. with gamma correction applied. On the other hand, libxine+vdpau seems to be used for both decoding and display, so it is IMO very likely that this is some special code entirely bypassing software processing.
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Old 03-27-10, 08:40 AM   #9
Muse ESUm
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Default Re: Gamma and brightness settings not working when using VDPAU

I was able to fix the issue. VDPAU supports an overlay path, and a blit path. With the overlay path (default if composite is disabled), no gamma correction is possible. To force the blit path, either enable compositing, or set the entironment variable VDPAU_NVIDIA_NO_OVERLAY=1. This might cause tearing with older vdpau drivers, but I didn't have such issues with recent nvidia drivers.
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