Timing Question

[ben robinson]

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 <emzcoffey 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.
>
> >
>

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups "E-Prime" group.
To post to this group, send email to e-prime at googlegroups.com
To unsubscribe from this group, send email to e-prime+unsubscribe at googlegroups.com
For more options, visit this group at http://groups.google.com/group/e-prime?hl=en
-~----------~----~----~----~------~----~------~--~---

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://listserv.linguistlist.org/pipermail/eprime/attachments/20090425/8e919cea/attachment.htm>