Timing Question

[Emz]

No luck with that... The starting vertical refresh was on, I tried
also with the ending one (no effect)

Reducing the times to more that 10ms just brings me to the next lower
refresh cycle multiple with the same variability.

I also tried setting the pre-release, but that had no effect at all...



On 26 apr, 14:15, "Carlos Cortes" <ccor... at mprc.umaryland.edu> wrote:
> Have you tried to sinc the stimulus to the vertical refresh?
>
> >>> emzcof... at gmail.com 04/26/09 6:17 AM >>>
>
> I will try it, but the problem is not so much the timing, but the
> consistency: if it were all 527ms it would be fine, but somehow I
> always get 2 different timings which are quite different.
>
> On Apr 25, 8:31 pm, ben robinson <baltimore.... at gmail.com> wrote:
>
>
>
> > have you tried adding more than just 10 ms as your buffer?  that is, if you
> > want something to display every 505 ms, and you set it to prepare the
> > display at 495 ms, yet it ends up actually displaying at 527 ms, why not try
> > preparing the display at 480 ms?  just a thought.
>
> > On Thu, Apr 23, 2009 at 2:28 PM, Emz <emzcof... at gmail.com> wrote:
>
> > > Hello,
>
> > > I need some help with a timing problem in a reasonably complex set-up
> > > (the complexity is in in-line scripts that output to another system,
> > > which requires the use of the IsPending() function, the task itself is
> > > just an N-back variant). I have tried and tested many minor changes in
> > > the set up and have managed to eliminate all of the timing problems
> > > except one: the actual duration of stimulus presentations are always
> > > either one of two values, each different than expected (as based on
> > > multiples of screen refresh rate).
>
> > > The specifics are as follows:
>
> > > The screen refresh rate is 75.031Hz, giving a duration of 13.3. I wish
> > > to have presentation times of about 500 ms and 2000 ms, so as per
> > > manual I have selected about 10 ms less than the nearest multiples
> > > (505.4 and 2008.3), resulting in the set presentation duration times
> > > set to 495ms and 2000ms.
>
> > > Errors are consistently as follows:
>
> > > 527.3438 - 505.4000 =  21.9438 (many more of this one)
>
> > > 558.5938 - 505.4000 =  53.1938 (only about 15% of the ~500 ms display
> > > items)
>
> > > 2027.3483 - 2008.3000 = 19.0483 (equal proportions with below for the
> > > ~2000ms items)
>
> > >  1996.1 * 2008.3 =  -12.2
>
> > > I am currently not using the pre-loading option as I read somewhere
> > > this was not necessary for this sort of task. I also have some in-line
> > > scripts between display items, and the before mentioned IsPending loop
> > > in some places, for which I don’t know if the pre-loading would even
> > > make sense. The aforementioned IsPending loop doesn’t seem to be the
> > > problem as trials with and without it have exactly the same errors.
> > > Deleting or moving the in-line scripts (which are used to output data)
> > > appear to produce a bigger variety of errors.
>
> > > Ideas ?
>
> > > E.- Tekst uit oorspronkelijk bericht niet weergeven -
>
> - Tekst uit oorspronkelijk bericht weergeven -
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