>Psychtoolbox>PsychHardware

PsychGPUTestAndTweakGammaTables - Test and tweak GPU hardware gamma tables.

This function is a helper function used for high-precision display
devices like the Bits# from CRS and DataPixx/ViewPixx/ProPixx from VPixx,
which need identity passthrough of framebuffer pixel data to the video outputs
without any interference by the GPU and other intermediate encoder circuitry.

It augments functions like LoadIdentityClut, trying to cope with GPUs that
are too broken to be fixable just by that function without any actual
measurement of video signals.
The function is called by toolboxes for special display output hardware
and makes use of / calls back into hardware specific functions of that
hardware to allow an iterative feedback loop of parameter tweaks and
measurements to execute in order to optimize gamma tables for optimal
pixel passthrough after other hardware-independent measures have failed.

The routine is, e.g., used by the ‘GPUEncoderTest’ / ‘CheckGPUSanity’
functions of the PsychDatapixx and BitsPlusPlus functions.

Input parameters: (Mandatory)
‘win’ = Onscreen window handle for onscreen window which displays to the
external high precision display device.

‘deviceType’ = Type of device: 0 = VPixx Inc. Data-/View-/Pro-Pixx.
1 = CRS Bits#

‘injectFault’ = 1 = Intentionally setup a slightly faulty LUT to perturb
the signal and test the tweaking procedure. 0 = Don’t.

Returns 0 on success, 1 on failure.