Mailinglist Archive: radeonhd (699 mails)

[Luc Verhaegen <libv@xxxxxxxxx>]

On Thu, Nov 01, 2007 at 09:22:22AM +0100, Pierre Ossman wrote:
> Hi,
>
> 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".

Could it be that it really is a 24bit panel and that, since we do not 
know any better, we set it up as an 18bit panel and it still works?
When i'm back in the office; i should probably try to set up the hp 
laptop as 24bits. This laptop is a mobility r5xx, 1680x1050, so i was 
initially quite surprised to see that it was only an 18bit panel. Iirc, 
i attempted to drive it differently, without success, but this was in 
the hectic days right before XDS.

> 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.

Please describe what you mean by grainy? Could there be something else 
going on besides dithering? I hope it is not something as 
straightforward as adjusting gamma.

> 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.

These are both for seperate outputs and will not influence your panel.

Luc Verhaegen.
SUSE/Novell X Driver Developer.
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