From mboxrd@z Thu Jan  1 00:00:00 1970
From: Thomas Richter <thor@math.tu-berlin.de>
Subject: 16bpp and 8bpp uxa output broken...
Date: Mon, 04 Nov 2013 00:56:32 +0100
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To: Daniel Vetter <daniel@ffwll.ch>
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Hi Daniel, dear intel experts,

just another note: I just switched the default depth from 24 to 16 bit 
by adding a "DefaultDepth" into
the screen section of X11. Strangely enough, that gives much *less* 
banding than the 24bpp output????

Anyhow, 16bpp breaks the gdm login, and 8bpp breaks almost everything. 
Strangely, if I switch from uxa
to sna, gdm is fine and the graphics is much smoother (less banding) 
than with 24bpp output.

Greetings,
     Thomas

P.S.: Strangely enough, with the 24bpp output, I can clearly count 64 
distinct grey levels corresponding to
the 6bpp panel (I assume), with 16bpp output, I get a somewhat more 
irregular banding (probably because
green has one bit more), though the desktop background is very smooth. 
The same image, when viewed
by eog, shows banding. Thus, I suppose, that the desktop renderer 
applies some kind of dithering while
eog does not. Wierd.