>Hello,dear dave
>
>My name is Dave, and I am working with Rhea Eskew.
>
>I have attached a copy of a screentest report. And I was hoping you would be
>able to help me interpret it.
>
>Thank you very much.
>
>
>--
>David Richters
>Northeastern University
>(617) 373-5057
thanks for sending in your reports. they reveal a surprising and possibly
important anomaly.
We routinely ask users of the PsychToolbox to attach a ScreenTest report
to their bug reports. You've also included a TimeVideo report. TimeVideo,
for those who don't know, is a much older free-standing application that
ScreenTest was originally based on. I wrote both. It's still available:
<http://vision.nyu.edu/VideoToolbox/Download.html>
The surprise is that TimeVideo indicates that your DualHead card is
working perfectly in every way, but that ScreenTest reports that it lacks
the desirable but optional feature of waiting for blanking when doing
SetClut. The two reports contradict each other on this point.
The simplest explanation is that the DualHead card supports the
relatively new optional Apple driver call that turns on and off waiting
for blanking by cscSetEntries (i.e. SetClut), but with a nonstandard
polarity. TimeVideo is older and doesn't know about this call, so it
simply leaves your card in the default state, which apparently has this
feature on. SCREEN or ScreenTest, to be helpful, tries to turn the
feature on, but apparently in fact turns it off. i'm guessing here, but
this would explain your symptoms.
I've enclosed an enhanced version of WaitBlankingTest that explicitly
tests this issue. Could you run it and email the results to the forum?
best
denis
ps
you can test my diagnosis in your programs by setting these three
preferences:
SCREEN(which,'Preference','AskSetClutDriverToWaitForBlanking',0); %
nonstandard polarity
SCREEN(which,'Preference','SetClutCallsWaitBlanking',0); % rely on
driver, not interrupt
SCREEN(which,'Preference','SetClutDriverWaitsForBlanking',1); % tell
psychtoolbox that driver waits
the preference settings are lost when you close the last window on a
device, so to do this test you may need to paste the three lines above
into your program at some point AFTER the first window is opened.
NOTE TO ALL: denis.pelli@... is my preferred email address. Please
use that address. My "verizon.net" address will go away soon, partly
because Verizon forces me to use that as my "From:" address. My current
email program won't allow me to designate a separate "Reply-to:" address.