Image display delay

[David McFarlane]

In addition to the suggestions from others, I just wonder whether 
your 8-14ms display delay is in *addition* to any normal delays 
resulting from onset synchronizion with the vertical blank of the 
screen.  That was why I referred you to Chapter 3.  As explained 
there, because of how video works you cannot avoid some delay in the 
onset of visual stimuli *unless* you make sure that all your times 
are exact multiples of the screen refresh time.  Just wanted to make 
sure we covered that possibility.

-- David McFarlane, Professional Faultfinder


At 4/14/2009 10:22 PM Tuesday, you wrote:
>Dear David
>         I have read Chapter 3 of Userguide thoroughly, but still 
> feel a little confusion. In each block of my programme, there was a 
> TextDisplay, a Inline Scripe and a ImageDisplay(stimulous).To 
> synchronize the signal of NeroScan and the stimuli of e-Prime, I 
> have inverted a in-line WritePort command before "ImageDisplay" and 
> set the PreRelease time (100ms) in the TextDisplay. However, the 
> unwanted delay or unsynchronization still existed between the 
> e-Prime and EEG recording system result in anormal delay of N170 
> component. Thus, I want to ask whether the WritePort command was 
> sent to the recording system at the beginning of Prelease time or 
> at the point when stimulous presents on the screen. In other word, 
> I want to know whether the WritePort command and image were sent at 
> the same time from E-Prime.
>       Thank you for your concerning.
> 
>
> > Date: Wed, 8 Apr 2009 11:26:12 -0400
> > To: e-prime at googlegroups.com
> > From: mcfarla9 at msu.edu
> > Subject: Re: Image display delay
> >
> >
> > At 4/5/2009 09:35 PM Sunday, maocong wrote:
> > >I am a greenhand in programming on e-prime, and I need some help on
> > >the fellowing issue:
> > >
> > >I designed an ERP visual stimulous experiment by using the control of
> > >ImageDisplay on e-Prime 2.0v and the EEG recording system is NeroScan
> > >4.3v. And I found a 8~14ms delay on image display(shown by the
> > >programme running result file), and the help file showed this delay is
> > >the difference between orignial onset time and actual display time.
> > >This random image display delay greatly effect the accuracy of N170
> > >latency recorded, which lead to the unreliablity of the experiment
> > >result. Therefore I hope you can give me some advices about how to
> > >eliminate/compensate this display delay or how to uniform this display
> > >delay
> >
> > Please read thoroughly chapter 3 ("Critical timing...") of the User's
> > Guide that came with E-Prime.
> >
> > -- David McFarlane, Professional Faultfinder



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