10-but LUTs and the Dell U2711

[Andrew Lutomirski]

On Wed, Jul 21, 2010 at 4:32 AM, Richard Hughes <hughsient at gmail.com> wrote:
> On 20 July 2010 20:06, Andrew Lutomirski <luto at mit.edu> wrote:
>> I have a Dell U2711, which has 10 bits per channel over DisplayPort
>> (although I'm not sure that anything other than i915 can drive 10 bits
>> right now, and even i915 needs bleeding-edge drivers).  Can GCM
>> program a 10-bit video card LUT?
>
> In theory, yes. I've made the GcmClut object generate the amount of
> data for each LUT size, but I admit I've never tested it on anything
> other than 8 bpp.
>
>> Also, the U2711 has an internal LUT, although no one seems to know how
>> to program it (even on Windows) or even whether it can be programmed
>> with anything other than a (not-very-good) factory calibration.
>> Richard, did your libcolor-glib work give you any ideas for how to
>> test for DDC control of a LUT on an unknown monitor?  I'd be happy to
>> test and fiddle.
>
> Yes. I'm still waiting for me DreamColor monitor to arrive, and that
> allows a custom colorspace to be uploaded. For your monitor, you
> probably need to convince the manufacturer to give you the specs, or
> find a windows tool that calibrates the monitor and then trace that.
>
> You always have to be a little but careful sending hardware random
> data to reverse engineer it. First, the output of "gcm-ddc-util
> --enumerate" should give us something to work on.

gcm-dump-edid says:

  Monitor name: DELL U2711
  Vendor name: Dell
  Serial number: D971T0471EFL
  PNP identifier: DEL
  Size: 60x34
  Gamma: 2.200000


gcm-ddc-util --enumerate says:

$ sudo ./gcm-ddc-util --enumerate
EDID:   f3b71e4fd0bf14ac3db509cbc4ba48ba
PNPID:  DELA055
Model:  U2711
0x02    [secondary-degauss]
0x04    [reset-factory-defaults]
0x05    [reset-brightness-and-contrast]
0x06    [reset-factory-geometry]
0x08    [reset-factory-default-color]
0x10    [brightness]
0x12    [contrast]
0x14    [select-color-preset]    ( 1 5 8 0 0 )
0x16    [red-video-gain]
0x18    [green-video-gain]
0x1a    [blue-video-gain]
0x52    [saturation]
0x60    [input-source-select]    ( 1 3 4 5 0 0 11 )
0xac    [horizontal-frequency]
0xae    [vertical-frequency]
0xb2    [unknown]
0xb6    [unknown]
0xc6    [unknown]
0xc8    [unknown]
0xc9    [firmware-version]
0xd6    [dpms-control-(1---on/4---stby)]         ( 1 4 5 )
0xdc    [magicbright-(1---text/2---internet/3---entertain/4---custom)]
  ( 0 2 3 4 5 )
0xdf    [vcp-version]
0xfd    [power-led]

--control 0xb2 --get doesn't seem to work.

This is also suspicious:

$ sudo ./gcm-ddc-util --display f3b71e4fd0bf14ac3db509cbc4ba48ba
--control vcp-version --get
vcp-version is 513, max is 255


I'm not really sure what I'm looking for, though, and I haven't
spotted the DreamColor code.  (Is it there?)

--Andy


>
> Richard.
>