[ monitorFlipInterval nrValidSamples stddev ] =Screen(‘GetFlipInterval’, windowPtr [, nrSamples] [, stddev] [, timeout]);
Returns an estimate of the monitor flip interval for the specified onscreen
“windowPtr” is the handle of the onscreen window for which info should be
“nrSamples” If left out, the estimated interval from previous calls to
GetFlipInterval or from the initial calibration done during
Screen(‘OpenWindow’…) is reported. If set to a value greater zero, PTB will
perform a measurement loop to compute a good estimate. The loop will run until
at least nrSamples valid samples have been taken and standard deviation of the
measurement is below “stddev” seconds. A timeout value “timeout” can be set to
abort the measurement after timeout seconds if the measurement doesn’t converge
for some reason. Timeout is 10 seconds and stddev is 50 microseconds by default.
PTB automatically takes at least 50 valid samples when opening an
onscreen-window, trying to achieve a standard deviation below 100 microseconds,
but timing out after a maximum of 15 seconds. If you require very high
precision, call this routine with values that suit your demands.
The returned monitorRefreshInterval is in seconds, but has sub-millisecond
accuracy. The real number of valid samples taken and the final standard
deviation is returned as well.
CAUTION: When using frame-sequential stereo (stereomode=1/11 in OpenWindow)), the
flip interval (as reported here) may be twice as long as the monitor refresh
interval. Using Anti-Aliasing with a high multiSample level at a high display
resolution may also cause the graphics hardware to switch to a flip-interval
twice as long as the monitor refresh interval, because it is not capable of
performing all anti-aliasing computations in one single refresh interval.