Unclear how to change configuration settings after Psych toolbox synchronization failure

Following failed sync tests for Demo files of the EyeLink II system, the first solution offered on the "SyncTrouble" help page (see below) is to reconfigure settings. I am unsure where/how to reconfigure the settings included in the below recommendations. I assume these setting changes are done directly on the computer and not through MATLAB? I am working from a PC and running MATLAB 2017b. Does anyone have recommendations for how to go about trying these troubleshooting steps?

>> help SyncTrouble

SyncTrouble -- Causes and solutions for synchronization problems.

You most probably arrived at this help page because Psychtoolbox

aborted with "SYNCHRONIZATION FAILURE" or a similar error message and

asked you to read this page.

BACKGROUND: Why proper synchronization to retrace is important.

When executing Screen('OpenWindow'), Psychtoolbox executes different

calibration routines to find out if back- and frontbuffer swaps (what

Screen('Flip') does) are properly synchronized to the vertical retrace

signal (also known as VBL) of your display. At the same time, it measures

the real monitor video refresh interval - the elapsed time between two

VBL signals. It is crucial for flicker free, tear free, properly timed

visual stimulus presentation that buffer swaps only happen during the VBL

period of the display. The VBL (vertical blank) is the small gap in time

that occurs when the display has updated its last scanline and before it

starts redrawing its display surface starting at the first scanline

again. This small gap is a neccessity for CRT displays and it is

preserved for compatibility reasons or other technical reasons on flat

panels and video beamers. After issuing the Screen('Flip') command, the

graphics hardware finalizes all pending drawing- and imageprocessing

operations in the backbuffer of an onscreen window to make sure that the

final stimulus image is ready in the backbuffer for presentation. Then it

waits for onset of the next VBL interval before flipp'ing the back- and

frontbuffer of the onscreen window: The previous backbuffer with your

newly drawn stimulus becomes the frontbuffer, so it will get scanned out

and displayed to the subject, starting with the next refresh cycle of

your display device and on all consecutive refresh cycles, until you draw

a new stimulus to the onscreen window and update the display again via

Screen('Flip').

On a properly working system, this double buffer swap happens in less

than a microsecond, synchronized to VBL onset with an accuracy of better

than a microsecond. All change of visual content therefore only happens

during the VBL period when the display is not updating, thereby avoiding

any kind of visual flicker or tearing that would be caused by a mixup of

an old stimulus and a new (incompletely drawn) stimulus when changing

image content during the scanout cycle of the display. The exact point in

time when this buffer swap happened, is returned as timestamp by the

Screen('Flip') command. It is the most well defined timestamp of visual

stimulus onset, and it allows to define stimulus onset of future stims

relative to this accurate baseline, using the 'when' argument of

Screen('Flip').

Without proper synchronization, you would see very strong visual flicker

and tearing artifacts in animated (movie / moving) stimuli, you would not

have any well defined stimulus onset for sequences of static stimuli or

rapid stimulus presentation, and no means of synchronizing visual

stimulus presentation to any external stimulation- or acquisition devices

like fMRI, EEG, sound, ... You also would not have any accurate way of

getting a stimulus onset timestamp.

However, if you have very special needs, you can disable either Matlabs /

Octaves synchronization of execution to the vertical retrace or you can

disable synchronization of stimulus onset to the vertical retrace

completely by setting the 'dontsync' flag of Screen('Flip') accordingly.

For more infos about tearing, see Wikipedia articles about "Tearing",

"Double buffering", "Vertical Synchronization" and the info pages on

www.psychtoolbox.org

TESTS: How Psychtoolbox tests for proper synchronization to retrace.

After opening an onscreen window, Psychtoolbox executes a measurement

loop, where it issues Screen('Flip') commands and measures the time

elapsed between execution of two consecutive flip commands, getting one

refresh sample per loop iteration. Each sample is checked for validity:

Duration must be longer than 4 milliseconds and shorter than 40

milliseconds, because we assume that none of the available display

devices updates slower than 25 Hz or faster than 250 Hz. Each sample is

also tested against the expected value provided by the operating system,

e.g., if the operating system reports a nominal refresh rate of 100 Hz,

then a sample should have a duration of roughly 1000 ms / 100 Hz == 10

milliseconds. We accept any sample in a range of +/- 20% around this

expected value as valid, because timing jitter present in any computer

system can cause some deviation from the expected value. Samples that

don't pass this basic test are rejected. Valid samples are used to update

a mean value, standard deviation of the mean is also calculated: The

measurement loop ends when at least 50 valid samples have been taken and

the standard deviation from the mean is less than 200 microseconds. If it

is not possible to satisfy this criteria during a five second measurement

interval, then the calibration is aborted and repeated for up to three

times. Failure to get a valid measurement during up to three calibration

runs is indicating massive timing problems or the inability of the

gfx-hardware to properly synchronize buffer swaps to the vertical

retrace. This leads to abortion with the "SYNCHRONIZATION FAILURE" error

message. Assuming that this calibration loop did provide a valid mean

measurement of monitor refresh, the value is checked against the value

reported by the operating system and - on MacOS-X - against the result of

an independent measurement loop that uses direct queries of rasterbeam

positions to measure the monitor refresh interval. Only if all available

measurements yield similar results, the test is finally rated as PASSED,

Psychtoolbox continues execution and the computed monitor refresh

interval is used internally for all built-in timing checks and for

properly timed stimulus presentation.

REASONS FOR FAILING THE SYNC TESTS AND HOW TO FIX THEM:

There are multiple classes of possible causes for sync failure. Work down

this list of causes and solutions down until your problem is resolved or

you hit the bottom of the list:

1. Wrong configuration settings: This usually only affects MS-Windows

systems, where the display settings control panel for your graphics card

allows to customize a couple of graphics driver parameters. Some of these

settings can cause sync failure if they are wrong:

-> Make sure the "Synchronize bufferswaps to the vertical retrace" option

is set to "Application controlled" or "Application controlled, default to

on". The wording of the option differs between different graphics cards,

search for something like that. Examples of other names: "Wait for

vertical sync", "Wait for vertical refresh" ... If this setting is forced

to off and *not* application controlled, then the sync tests will fail

because the hardware doesn't synchronize its image onset (bufferswap) to

the video refresh cycle of your display.

-> Make sure the "Triple buffering" setting is off, or if you can select

some "Multibuffering" setting, that it is set to "double buffering" or

"wait for 1 video refresh" or "swap every refresh". This option may not

exist, but if it does, any other setting will cause the sync tests to

possibly succeed, but later stimulus onset timestamping to fail with

errors.

-> If there is an option "Buffer swap mode" or "Bufferswap strategy", it

should be set to "Auto select" or "Page flipping" or "Exchange buffers".

The so called "Copy buffers" or "Blitting" option would result in lower

performance and inaccurate timing.

-> On dual/multi display setups MS-Windows allows you to assign one

monitor the role of the "primary monitor" or "primary display". It is

important that the display device which you use for stimulus presentation

is the "primary display", otherwise random things may go wrong wrt. sync

tests and timing.

-> If you have the choice to set your multi-monitor configuration to

either "dual display mode"/"dual display performance mode"/"separate

displays" or instead to "extended desktop mode" or "horizontal spanning",

you should choose "extended desktop mode" or "horizontal spanning" modes

for best timing and stimulus quality. Please note that this choice

doesn't exist anymore on Windows-Vista and later.

-> On all operating systems in dual display or multi display mode it is

important that you configure both displays for exactly the same color

depths, resolution and refresh rate if you want to present stimuli across

multiple displays, e.g., for binocular stereoscopic presentation on a

dual-display setup. If there is some option you can choose for "genlocked

modes" or "genlocked modes only", choose or enable that one. Failing to

configure dual display setups like this will cause massive timing

problems or tearing artifacts on one of the display if you do dual

display stimulation. It may also cause failures in timetamping.

[Walter Roberson]

"the display settings control panel for your graphics card"

[Zhan Anya]

Hi, I also encountered the same problem. Hope my answer helps (though it has passed 2 years).

For the first three, I will use "Synchronize bufferswaps to the vertical retrace" as an example, as the three are displayed on the same page.

If you want to set the "Synchronize bufferswaps to the vertical retrace" option to 'application controlled' in MATLAB, you will need to access the graphics card driver settings. The specific steps to access the settings may vary depending on your graphics card and operating system. Here are some general steps that may help:

1. Right-click on the desktop and select "Graphics Properties" or "NVIDIA Control Panel" (or similar).
2. Navigate to the "3D Settings" or "Display" section.
3. Look for an option related to vertical synchronization, vertical refresh rate, or buffer swaps. Depending on your graphics card and driver version, the option may be called "Vertical Sync," "Vertical Refresh," "Buffer Swap," or similar.
4. Set the option to "Application Controlled" or a similar value that allows the application (in this case, MATLAB) to control the buffer swaps.

For 'dual/multi display' in Windows, please follow the steps below:

1. Connect your additional monitor(s) to your computer.
2. Right-click on the desktop and select "Display settings" from the dropdown menu.
3. Scroll down to the "Multiple displays" section and select the option that best fits your needs, such as "Extend desktop" to use your additional display(s) as an extension of your primary display or "Duplicate desktop" to duplicate your primary display on all connected displays.
4. Adjust the resolution and orientation of each display as needed using the dropdown menus and settings available under the "Multiple displays" section.
5. Click "Apply" and then "Keep changes" to save your display settings.

Although I tried these steps, none worked for my computer. I think that may be the hardware issues.