timing error

[David McFarlane]

Tobias,

I just noticed in your post that started this thread you said that 
you use vertical blank for both Onset Sync and Offset Sync.  In 
general, for visual display objects I would set Onset Sync to 
vertical blank, and Offset sync to (none), which is the default (I 
leave it as an exercise for you to ponder why this makes sense).  But 
if you instead used a Wait object for your ISI then, as Mich 
mentioned, I might set both Onset Sync and Offset Sync to (none) and 
then duration should work as expected.  Even then I would rather 
follow Mich's further advice to either use a bit of inline script to 
skip past the ISI, or use a separate Procedure without the ISI, 
whenever the ISI duration is 0.  You might be surprised at how much 
script will run in less than a millisecond.  As you read in Chapter 
3, the real time bottlenecks are disk access (e.g., loading image and 
sound files), display synchronization, and interruptions from the 
operating system.  But don't take my word for this.  You can time 
script yourself using the microsecond clock in E-Prime (see the Clock 
topic in the online E-Basic Help).

-- David McFarlane, Professional Faultfinder


At 1/14/2010 07:51 AM Thursday, you wrote:
>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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