ATI oss color space compressed in the dark shades of gray

Sebastian Schultz sebastian2.schultz at
Wed Mar 12 07:31:23 PDT 2014


first of all: I'm using a Radeon 7750 in combination with a monitor via 
display port and a tv via the HDMI port. Most of the time I do not want a 
picture on the tv, only when wathcing videos, so I use xrandr scripts to 
switch that display on and off. And here comes my problem:

With the arrival of linux 3.13 to the [core]-repo of arch linux I switched 
from catalyst to the open source drivers, as they finally provide a sufficient 
performance. My only problem now is that the colorspace is compressed for gray 
values below 16 (that means every shade of gray having values of 0 to 16 look 
just black). That's only the case for my HDMI-output connected to my TV, which 
worked without problems with the catalyst drivers. Also, only the dark grays 
are compressed, the near-white grays show up correct.  My Xorg.0.log shows 
that the TV on HDMI-0 supports the RGB 4:4:4 encoding (just like the monitor 

I found a xrandr-command "--set "Broadcast RGB" "Full"", which can be used 
with chips from Intel. Is there something similar for the open source ati 


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