[i915] Backlight brighter since 3.9.0

[Daniel Vetter]

On Wed, May 22, 2013 at 6:08 PM, Joakim Plate <elupus at ecce.se> wrote:
>> 2013/5/20 Daniel Vetter <daniel <at> ffwll.ch>
>> Yeah, this is a feature. HDMI has (for oddball backwards compat with
>> analog TV signals) a special mode which reduces the useable RGB value
>> range by chopping off about 10% at the bottom and top end. This results in
>> light colors getting brighter and dark colors getting darker.
>> The above mentioned commit tries (to the best of our knowledge) to
>> auto-set the option which most likely fits what the hdmi sink will do with
>> the color data. You can either fix this up in the hdmi sink with the
>> on-screen menu or by manually setting the "RBG Broadcast" property for the
>> relevant hdmi connector to the setting you want.
>> Cheers, Daniel--
>> Daniel Vetter
>> Software Engineer, Intel Corporation+41 (0) 79 365 57 48 -
> http://blog.ffwll.ch
>>
>
> Does this mean the system is doing RGB full range to limited range
> compression on the raw RGB data it receives from an application?
>
> Ie a video player that want to be able to handle blacker than black
> properly will need to force the GPU into fullrange output to avoid
> the driver internal compression of the signal and handle that itself?

At least on the display I've seen limited range indeed seems to indeed
clamp and full white/black. But ofc if your media player already
outputs limited range, then you need to disable the gpu side ranger
compression.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch