Mailinglist Archive: radeonhd (699 mails)

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[radeonhd] Dithering, how to disable
  • From: Pierre Ossman <drzeus-list@xxxxxxxxx>
  • Date: Thu, 1 Nov 2007 09:22:22 +0100
  • Message-id: <20071101092222.7cc51b82@xxxxxxxxxxxxxxxxxx>

It seems that Lenovo doesn't really believe in the concept of truth in
marketing. The panel advertised as 24-bit is actually 18-bit (they claim 16.7 M
colors, not 16.2 M or the actual 262 k). To compensate, there is some dithering
involved, and seems to give an effect most people describe as "sparkling".

This grainy, or sparkly, appearance is a bit annoying and might be the reason
why I perceive this display as straining. So I'd like to disable it and see if
that makes me a happy camper.

I've been fiddling with the register LVTMA_BIT_DEPTH_CONTROL, disabling the
relevant dither bits there. That does indeed remove so much of the dithering
that you can start seeing the banding caused by the 18-bit truncation.
Unfortunately, the display is still grainy, so something is still active.

So my question is if there are more things I can tweak or if the remaining
issue is just a property of the matrix. TMDSA_BIT_DEPTH_CONTROL seems to be
just for TMDS (which is just for DVI?), but there's also a
DVOA_BIT_DEPTH_CONTROL which I'm unsure where it fits in.

Grateful for any help.

-- Pierre Ossman

Linux kernel, MMC maintainer
PulseAudio, core developer
rdesktop, core developer
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