BitsPlusIdentityClutTest

Psychtoolbox › PsychHardware › BitsPlusToolbox › BitsPlusTests

Test proper function of the T-Lock mechanism, proper loading of identity
gamma tables into the GPU, and for bad interference of dithering hardware
with the DVI stream. This test is meant for Mono++ mode of Bits+, it
won't work properly in any other mode!!

Disclaimer: This test only exists because of the huge number of serious &
embarassing bugs in the graphics drivers and operating systems from
Microsoft, Apple, AMD and NVidia. All problems diagnosed here are neither
defects in the Bits+ device or similar devices, nor Psychtoolbox bugs. As
such, sadly they are mostly out of our control and there is only a
limited number of ways we can try to help you to workaround the problems
caused by miserable workmanship and insufficient quality control at those big
companies.

Usage:

BitsPlusIdentityClutTest([whichScreen=max][usedpixx=0]);

How to test:

1. Make sure your Bits+ box is switched to Mono++ mode by uploading the
proper firmware.

2. Run the BitsPlusImagingPipelineTest script to validate that your
graphics card can create properly formatted images in the framebuffer
for Bits+.

3. Run this script, optionally passing a screenid. It will test the
secondary display on a multi-display setup by default, or the external
display on a laptop.

If everything works, what you see onscreen should match the description
in the blue text that is displayed.

If a wrong gamma lut is uploaded into your GPU due to operating system
and graphics driver bugs, you can try to toggle through different
alternative lut's by repeatedly pressing the SPACE key and seeing if the
display changes for the better. Should you find a setting that works, you
can press the 's' key to save this configuration and Psychtoolbox will
use this setting in all future sessions of your experiment scripts.

You can exit the test by pressing the ESCape key, regardless if it was
successfull or not.

What could also happen is that you get a partial success: The display
behaves roughly as described in the text, but you see the T-Lock color
code line at the top of your display erratically appearing and
disappearing - flickering. You also don't see a smooth animation of the
drifting horizontal red gradient or a regular cycling of the "COLORFUL"
words, but some jerky, irregular, jumpy animation, which may only update
a few times per second, or even only once every couple seconds or at very
irregular intervals. You may also see the display overlayed with random
colorful speckles, or you may not see the gray background image and gray
rotating gradient patch at all. In that case, the lut uploaded in your
GPU may be correct, but due to some serious graphics driver or operating
system bug, the GPU is applying spatial or temporal dithering to the
video stream which will confuse the Bits+ and cause random artifacts and
failure of the T-Lock mechanism.

You should also double-check the cabling and connections to rule out
connection problems and other defects.

In that case, contact CRS support or check the Psychtoolbox Wiki for a
workaround. Currently we have a workaround for MacOS/X systems, but not
for MS-Windows systems.