[argyllcms] Re: AW: Matrox P650 doesn't seem to want to play...

  • From: Neil Woolford <neil@xxxxxxxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Wed, 13 Dec 2006 14:21:37 +0000

Thanks for the swift and helpful responses guys.

On Wed, 2006-12-13 at 23:18 +1100, Graeme Gill wrote:
> Thomas Kumlehn wrote:
> > I'm not sure if this is related to the P650, but some graphics cards have
> > great 10bit LUTs but bypass them when outputting digitally over DVI, just
> > because they are placed by design between Memory path and DAC and not also
> > between Memory path and DVI chip. Currently no off-the-shelf LCD known to 
> > me,
> > takes 10bit per colour channel. All need 8x3bits.
> If the design of the card is such that the LUTs are only in the D/A
> path, then calibration isn't going to work. I'd be a little surprised if
> Video cards are designed that way (how are gamers going to adjust
> their gamma ?), but it's certainly possible. Of course DVI makes
> it impossible/non-standard to use more than 8 bits/component,
> so an Video cards LUTs will be 8x3 to the DVI.

It sounds horribly like what may be happening.  No error message when
writing to the LUT, but no effect either.  That could mean I'm
successfully writing to the table but it has no effect on the outputs
that I'm using.  I suppose I have to hope that the main screen (a
Formac) lives up to the manufacturer's claim of great image quality
straight out of the box.  The second monitor is just for palettes and
tools so really a manual adjustment to a non-offensive visual match on
the white would be enough for comfort.

Next thing I'll try is reverting the secondary display to analogue
connection and see what happens then when I run dispwin -r on it.  If
that works, then I think we have our answer.  I'll research the Formac
documentation, just in case there is something internal to the monitor.

I did quickly try messing with the xgamma command, which had the
expected effect within X.  I also temporarily reverted to a single
monitor setup without changing the symptoms, so Xinerama probably isn't
to blame.

I'm using the mta driver in X, which I did have to install specially;
there appear to be some kernel modules which are associated with this
which didn't compile successfully - I think that looses me 3d gizmos
that I don't use, but there may be other things of importance lacking
because of that.  I'll check that.


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