timing error

[Michiel Spape]

Hi Tobias,
You did actually turn OnsetSync OFF, didn't you (I mean, with onsetsync or offsetsync on, it's not very strange it uses at least one cycle). I seem to recall, however, that 0 ms textdisplays and such did 'flash' before my eyes, which would appear to mean it's a bit longer than 0 ms anyway! Still, I don't find it a particularly nasty problem, because, as you say, a tiny piece of script (if ISI.duration = 0 then goto label1 'label1 being just after ISI) should solve the problem immediately. There's absolutely no reason why a script of this sort should take longer than a few nanoseconds to be processed, especially as compared to setting up a slide which in the end *should not even show*. There are, however, many more ways around this, even without script. You could, for example, just use a different procedure for conditions in which ISI is 0, that is, without the ISI there at all - that would also immediately take care of the problem and would be, in a way, even more efficient processor-wise.
Cheers,
Mich

Michiel Spapé
Research Fellow
Perception & Action group
University of Nottingham
School of Psychology


-----Original Message-----
From: e-prime at googlegroups.com [mailto:e-prime at googlegroups.com] On Behalf Of Tobi
Sent: 14 January 2010 12:52
To: E-Prime
Subject: Re: timing error

Okay, after having read the entire Chapter 3 I found out that I have actually done everything right in terms of setting. However I found the reason for the timing error having a closer look at the result file. The timing error was always there in case the slide "ISI"
between the slides "Cue" and "Target" had the duration variable 0. I also used other durations for "ISI", specified in the block list. As a slide always uses at least on circle, the timing error then occurs even when using OnsetSync function.

This seems to be a serious problem. Do you have any idea how to solve this problem? I could maybe use a script asking for the ISI duration value and skipping the "ISI" slide when duration is 0. However a script in a short sequence of stimuli might also cause some timing problems. Maybe you have a better idea?

BEst,
Tobias

On 14 Jan., 01:33, Tobi <tobias... at gmail.com> wrote:
> Thanks David,
>
> I just found the User's Guide. I will read the 50 pages of chapter 3, 
> I promise.
> Could you or anyone give me a hint for my special problem anyway?
>
> Thanks a lot,
> Tobias
>
> On 13 Jan., 14:45, David McFarlane <mcfar... at msu.edu> wrote:
>
> > Tobias,
>
> > Everything you need to know about critical timing is in Chapter 3 of 
> > the User's Guide that came with E-Prime.  Go study that now.  Do not 
> > pass Go, do not collect $200.
>
> > -- David McFarlane, Professional Faultfinder
>
> > > Hi everyone,
>
> > > I am apparently having a timing error. In a procedure I use a 
> > > slide called "target". I display it for 78 ms on a screen with 100 
> > > Hz which should result in display times of 80 ms. In the result 
> > > file I find "target.OnsetDelay" values of either 2 ms (as wished) or 20 ms.
> > > "target.DurationError" is 33 ms.
>
> > > I used "vertical blank" for "OffsetSync" and "OnsetSync" and 100 
> > > ms of pre-release time to virtually avoid such errors.
>
> > > Another slide beeing displayed before the target (98 ms, same
> > > settings) does not show this error.
>
> > > Does anyone have an idea what this error could result from?
>
> > > Thanks a lot,
> > > Tobias
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