PDA

View Full Version : Contrast & Brightness control?


ronie
2009-02-07, 03:41
I ran into the problem that there were no contrast and brightness controls available in the OSD video settings on my Intel G45 based HTPC (GMA X4500HD graphics controller).
They do however show up on my PC with a NVIDIA graphic card, so i figured it must be some kind of hardware related issue.

After googling around for it bit i found that XBMC is doing a check for 'GL_ARB_imaging' in LinuxRendererGL.cpp and glxinfo on my HTPC indeed doesn't list this extension.

I decided to go ahead anyway and forced the check for CLinuxRendererGL::SupportsBrightness() and CLinuxRendererGL::SupportsContrast() in LinuxRendererGL.cpp to always return true.
Now the contast and brightness controls are showing up in the OSD and they are fully functional.

From what i found out browsing the interweb the 'GL_ARB_imaging' extension is widely available on NVIDIA cards, but only a few ATI cards support it and it is nonexistent on Intel based graphic controllers.
Based on this i guess many users are missing the contrast/brightness controls, although they could be working on their system.

So now i'm wondering if i should open a TRAC case for proper contrast / brightness support detection in XBMC, or am i missing something ?
Or maybe i'm just dead wrong (i'm no OpenGL expert).

proctor
2009-02-07, 04:33
Interesting find. I'm going to play around with this.

kimp93
2009-05-15, 10:15
Please do report a issue in trac.

ronie
2009-05-17, 16:32
Please do report a issue in trac.

I never created a ticket because it looks like if you're graphic card doesn't support the OpenGL 'GL_ARB_imaging' extension,
then contrast/brightness control is done in software instead of hardware.
The result is a 10% increase in CPU usage (on a 3GHz core2duo) as soon as you adjust those controls.

Not sure if people would want brightness/contrast control anyway, at the cost of a higher CPU load?