ATI 9100 IGP TV Out - brightness control?

Mark Knecht markknecht at
Thu Aug 13 09:18:31 PDT 2009

On Tue, Aug 11, 2009 at 6:54 PM, Alex Deucher<alexdeucher at> wrote:
> 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
> screen.
> Alex
   Thanks. I'll look into it but on Gentoo I think this is sort of
difficult to do as the system builds all the code. I'm not a
programmer so it seems likely I'll just create more problems than I'll

   If you do happen to expose these as variables I can set in
xorg.conf in a version I could get through portage then I'd be happy
to do some testing and report back.


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