[argyllcms] Re: Multiple issues with Argyll, please help

  • From: Rajiv Mehra <to_rajivmehra@xxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Tue, 2 Sep 2008 09:12:53 -0700 (PDT)

Oh great ! I will wait for the updated driver.
My CRT Video projector can display absolute black absolutely.......I mean it 
can show black as real black.......most current digital LCD/DLP/SXRD projectors 
can't do that. But this creates problems when we try to use a instrument to 
read low IRE percentages.
For example:
When Argyll tries to read black.........or patches with low IRE/brightness it 
usually takes pretty long.
With HCFR software I have regularly seen that it takes around 2 minutes to read 
10 % IRE patterns. I have also set HCFR to take multiple readings at low IREs 
and compute a average........this improves accuracy at low IREs but increases 
the time for taking readings. I wish Argyll could do the same.
May I suggest this feature in Argyll?:-
Allow an option to take multiple readings at low IRE patches and average them?

 Regards,
Rajiv Mehra



----- Original Message ----
From: Graeme Gill <graeme@xxxxxxxxxxxxx>
To: argyllcms@xxxxxxxxxxxxx
Sent: Sunday, August 31, 2008 7:28:50 AM
Subject: [argyllcms] Re: Multiple issues with Argyll, please help

Rajiv Mehra wrote:
> yes, there is something wrong somewhere. I dont know where to start looking. 
> All I know
> is ....if I remove and reinsert the USB plug of the instrument, Argyll works 
> fine for a
> few minutes more and craps out. Isn't the Argyll driver in question here?

Well seems that in testing dispcal on Vista, purely by accident, I have
observer a problem very similar to the one you describe.

It seems that Microsoft in their infinite wisdom, have changed the
behavior of the SetThreadExecutionState() in Vista so that it
no longer resets the Screen Saver timeout. This meant that in the process
of testing dispcal, the screensaver started on me, and it seems that
the particular screen saver I had chosen exposes the instrument to
low level illumination that changes dynamically (or perhaps it's low level,
colored illumination), and that sometimes triggers a timeout in the driver
that I haven't seen under any other circumstance, including very low
levels of constant illumination.

It seems that 30 seconds is insufficient, and that sometimes the
instrument takes over 60 seconds under these conditions.
So increasing the timeout time solves the problem, although
I wonder what the circumstances are that are triggering it (ie. what it
is about you projector output), and I wonder what the instrument is up
to, since a minute is a long time to take a reading.

I'll see about including the change in the next release.
Note that the libusb-win32 driver will need to be re-installed
for this updated version, since it has a maximum USB control
timeout hard coded into it.

Graeme Gill.

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