Timing Question

[Carlos Cortes]

Options:

1. Check what rates your video card can handle and change it to what's more convenient

2. There is software that force refreshing rates and give you different options for rate.

That's all I can think for now


>>> emzcoffey at gmail.com 04/28/09 7:19 AM >>>

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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