Warning and Screen error

Programming Help
1

So here is my error message! maybe someone has encountred it!
(for the record, I am trying to run this line: [win1,winRect] = Screen(‘OpenOffscreenWindow’,-1,[128 128 128]); %-1 )

PTB-WARNING: Mismatch between measured monitor refresh intervals! This indicates problems with rasterbeam position queries.

----- ! PTB - WARNING: SYNCHRONIZATION TROUBLE ! -----

One or more internal checks (see Warnings above) indicate that
queries of rasterbeam position are not properly working for your setup.

Psychtoolbox will work around this by using a different timing algorithm,
but it will cause Screen(‘Flip’) to report less accurate/robust timestamps
for stimulus timing.
Read ‘help BeampositionQueries’ for more info and troubleshooting tips.

Error in function OpenOffscreenWindow: Usage error
Could not find any open onscreen window to act as parent for this offscreen window. Open an onscreen window first!
Error using Screen
Usage:

[windowPtr,rect]=Screen(‘OpenOffscreenWindow’,windowPtrOrScreenNumber [,color] [,rect] [,pixelSize] [,specialFlags]
[,multiSample]);

Error in MLDS_2AFC_TaskA (line 167)
[win1,winRect] = Screen(‘OpenOffscreenWindow’,-1,[128 128 128]); %-1

2

Have you read the message? It says:
One or more internal checks (see Warnings above) indicate that
queries of rasterbeam position are not properly working for your setup.

So see above and follow the many suggestions there

3

The most important one apart from the broken timing warnings is:

Error in function OpenOffscreenWindow: Usage error Could not find any open onscreen window to act as parent for this offscreen window. Open an onscreen window first!

No onscreen window is open, so no offscreen window can be opened, as it requires such a onscreen window as parent.

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