[Openicc] EDID decoding in libXrandr?

[Hal V. Engel]

Sorry, sent this to the wrong list.

On Monday 19 November 2007 12:05:30 Hal V. Engel wrote:
> On Monday 19 November 2007 11:10:51 Kai-Uwe Behrmann wrote:
> > Why not reply to the xorg list? I think they should see our conversion to
> > better understand the interessts we colour people have there.
>
> Sorry that is what I intended to do.  Must have pushed the wrong button.
>
> > I am afraid I have to switch to non digest mode to not break the
> > discussion threads. Hope then my messages will be more readable.
> >
> > Am 19.11.07, 10:37 -0800 schrieb Hal V. Engel:
> > > On Monday 19 November 2007 06:46:40 you wrote:
> > > > > Date: Sun, 18 Nov 2007 09:29:30 -0800
> > > > > From: "Hal V. Engel" <hvengel at astound.net>
> > > > > On Sunday 18 November 2007 01:00:53 Kai-Uwe Behrmann wrote:
> > > > > snip
> > > > >
> > > > > > Not shure if the colorimetry information will make sense for some
> > > > > > people. I mean the RGB primaries and the witepoint from position
> > > > > > 25 till 34 and gamma in 23.
> > > > > > As I see, this information is dangerous for broken monitor EDID's
> > > > > > and of not much value for most of the others. Still it is there.
> > > > >
> > > > > Assuming that this info is (partly) valid for cases were the EDID
> > > > > is not broken then this could be useful.  For example LProfs
> > > > > visually based monitor profiler could use the RGB primaries and
> > > > > maybe the whitepoint information. But that also means that as a
> > > > > consumer of this information I also need to be able to query X as
> > > > > to how broken EDID is for the device in question.
> > > >
> > > > Agreed with the EDID borken status to be asked first before use. Just
> > > > the EDID colorimetry information may be broken in that sense that
> > > > most monitor manufacturers, or who else provides the EDID blob, dont
> > > > much care about that information. That said, even in a otherwise
> > > > valid EDID block can stand garbage or simply sRGB coordinates in the
> > > > colorimetry section of EDID.
> > > > That may be the reason why it is not much used on other platforms. I
> > > > remember a small little application, which parsed the EDID block to
> > > > create a profile.
> > > > ... ddc2xdccc.c  Interesstingly it creates a deprecated XDCCC block.
> > > >
> > > > If you can render say 90% of the monitors have a better than nothing
> > > > colorimetry in EDID, then the according buttons in LProf may have
> > > > technical value. At least you should check for swapping and non
> > > > relevant values.
> > > >
> > > > Last but not least some users may be irritated to get the inbuild
> > > > colorimetry straight from the monitor without a mesurement device -
> > > > huh. Will be difficult to explain later why they should by a
> > > > colorimeter, which may cost more than the complete monitor if they
> > > > have the inbuild data already ;-)
> > > >
> > > >
> > > > kind regards
> > > > Kai-Uwe Behrmann
> > >
> > > Unless the monitor has perfect response curves and gray balance, which
> > > is not very likely, we need more than the primaries and white point to
> > > do calibration and profiling correctly.   Using a color meter or
> > > spectrophotometer should always be preferred to using the values
> > > supplied by the monitor vendor in the EDID even if the EDID data was
> > > totally correct when the monitor left the factory.  This is the case
> > > because it is possible to compensate for nonlinearities in the the
> > > response curves of the device when using a measurement device.   In
> > > addition, monitors change over time and as the monitor gets older it's
> > > colorimetric data changes while the EDID will not change to reflect
> > > this.    For those users who can not afford a meter having good info
> > > about the primaries and white point gets us part of the way there at no
> > > cost.  So this would be a "poor mans" solution but it is far from
> > > optimal.
> > >
> > > Color meters are now fairly inexpensive and only very low end monitors
> > > are less costly than some current measurement hardware.  For example,
> > > you can purchase X-Rite Huey meters on eBay for about $50 plus shipping
> > > and these are now supported on X11 systems by both LProf (CVS) and
> > > ArgyllCMS (0.70 beta 7). The Huey has some minor issues but in my
> > > testing so far I have been pleased with the results.  I do, however,
> > > prefer the X-Rite EyeOne Display 2/Lt meters which can be purchased for
> > > about $130 (some times less) if you shop around.  Users should stay
> > > away from the ColorVision line of devices because the vendor has a very
> > > bad attitude toward the OSS community.
> >
> > Shame over Ross who bought one device from ColorVision despite the non
> > moralic, reads open source friendly, behaviour of that company ;-)
> > Indeed I am really happy that we get specs and the some time ago big
> > barrier seems to break. ColorVision is can now be considered more a
> > exception.
>
> We are not getting specs from any of these companies and in every case
> their relationship with the OSS community is less than ideal.  But at least
> the X-Rite folks are talking to us and are trying to understand how to work
> with us even if they have a ways to go.  ColorVision does not even try to
> hide their distain for us.   Like I said a VERY bad attitude.
>
> > The next target would be the monitor inside LUT. What does you think?
>
> We have looked a little at the Ezio LCD monitors which appear to expose the
> monitors internal LUT via the USB HID monitor controls.   One of our
> developers has the Ezio USB HID SDK (which really just documents the
> interface) and Ezio seems to be fairly open about this and appears to be
> willing to work with the OSS community.   So it is possible that this could
> be made to work at least for some monitors since this would not be much
> different from what we currently do to calibrate the dispaly using the
> video card gamma tables.   But I don't know if it will be possible to
> generalize this to work for more than a few vendors monitors.
>
> > > As a side note there was one freeware (or was it shareware) Windows
> > > application available at one point that used the EDID colorimetric data
> > > to create monitor profiles.
> >
> > Interresting. What was the over all experience with this application?
>
> I never used it and I don't know anyone who has so I can't comment on it
> beyond the fact that it existed.
>
> > > Hal
> >
> > Kai-Uwe
>
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