ATI oss color space compressed in the dark shades of gray

Alex Deucher alexdeucher at
Wed Mar 12 09:18:37 PDT 2014

On Wed, Mar 12, 2014 at 10:31 AM, Sebastian Schultz
<sebastian2.schultz at> wrote:
> Hello,
> 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
> does):
> 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
> drivers?

Not at the moment.


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