ATI 9100 IGP TV Out - brightness control?

Alex Deucher alexdeucher at
Tue Aug 11 18:54:45 PDT 2009

On Mon, Aug 10, 2009 at 7:38 PM, Mark Knecht<markknecht at> wrote:
> Hello,
>   I'm successfully using the newer Open source Radeon driver with my
> 3 Asus Pundit-R 9100 IGP machines. All 3 PCs drive different older TVs
> using their S-video inputs. This was something that for years I had to
> do with the ATI driver and am now very happy that it works so well
> with the Open Source driver.
>   One thing we are finding with this new driver is that the overall
> color level of the picture using S-video only is MUCH darker than the
> older fglrx driver. Even with the brightness turned all the way up on
> the TVs it's still doesn't get to the level that the older ATI driver
> did with brightness at a midrange setting. I'm wondering if there is
> possibly some settings in the xorg.conf file that might be able to
> improve this?
>   Note that this is NOT a problem for the same driver driving a
> normal monitor - it's only dark using the TVout.

You can mess with the RGB_ATTEN_VAL field of TV_RGB_CNTL.  See
radeon_tv.c.  I had thought about exposing it as a brightness option
for tv-out but never got around to it.  Note that setting it too low
(or high, I don't remember which) causes noise in white areas of the


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