[Intel-gfx] [PATCH] drm/i915: Use spatio-temporal dithering on PCH

[Adam Jackson]

On Wed, 2010-05-05 at 10:52 -0700, Carl Worth wrote:

> I'm going through the past couple weeks of traffic on the list looking
> for patches that haven't gotten picked up yet.
> 
> So I'd love to review one like this, but it would be easier if the
> commit message pointed me to something specific I could look at to see
> the difference.
> 
> So, do you have a little bit more in the way of details to help out
> someone as clueless as me?

I noticed this with:

http://ajax.fedorapeople.org/YellowFlower.jpg

set as my desktop background in Gnome on a 1280x800 machine (in
particular, a Sony Vaio VPCB1 with 6-bit panel and a rather bright black
level).  Easiest way to test this is by poking at PIPEACONF with
intel_reg_write directly:

% sudo intel_reg_write 0x70008 0xc0000040 # no dither
% sudo intel_reg_write 0x70008 0xc0000050 # spatial
% sudo intel_reg_write 0x70008 0xc0000054 # ST

I notice it especially strongly in the relatively flat dark area in the
top left.  Closer than about 18" I can see a noticeable checkerboard
pattern with plain spatial dithering.  ST smooths that out; I can still
tell that it's lacking color precision, but it's not offensive.

- ajax
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