What's best for E-Prime video timing accuracy: Mirror mode, VGA splitter, or Display Port splitter?

[David McFarlane]

Scott,

Good questions, wish I had an answer, hope someone else does.  You 
should submit this to PST Web Support at 
http://support.pstnet.com/e%2Dprime/support/login.asp , after all it 
is their business to know these things.  Then please post back here 
with the answer.

Thanks,
-- David McFarlane


At 12/9/2012 05:08 PM Sunday, Scott wrote:
>I don't expect perfection, but would like feedback to help choose 
>how to setup a new lab using E-Prime using physiological equipment 
>in two rooms. One room has two PCs, one recording physiological 
>measurements, connected (via the parallel port) to a second PC 
>running E-Prime. Each will be monitored by experimenters in that 
>room. The other room has the subject's video display and button box. 
>My question has to do ONLY with the E-Prime PC. We want 
>experimenters to be able to see what the subject sees, while they 
>monitor physiological recording, so we want the E-Prime video 
>mirrored on LCD displays in the two rooms. Of course this is a very 
>common situation for such labs (using EEG, fMRI, EDR, etc). Our 
>E-Prime computer has a video card (AMD RADEON HD 7470) with one 
>Display Port and one VGA port. Using this computer and display card, 
>there are 3 simple ways (afaik) to accomplish what I want and 
>display the same thing on two monitors:
>    * Connect one LCD to the Display Port and the other to the VGA 
> port, and set the display card to clone mode;
>    * Connect a VGA Y-splitter to the computer's VGA port, and 
> connect one LCD monitor to each side of the splitter; or
>    * Connect a Display Port Y-splitter to the computer's VGA port, 
> and connect one LCD monitor (via Display Port-to-HDMI or -to-VGA 
> converter) to each side of the splitter.
>
>Using method #1, the E-Prime 2.0.10.184 or later Experiment Advisor 
>will warn that "Mirroring can cause timing issues since vertical 
>blank synchronization is not accurate between multiple displays..." 
>(see <http://www.pstnet.com/support/kb.asp?TopicID=5014>KB 5014 - 
>FEATURE: Experiment Advisor Module - Display adapter set to clone 
>mode). However, I do not know whether using a splitter will actually 
>improve timing consistency or solve any issues related to vertical 
>blank synchronization. If a splitter would be better, Also, I don't 
>know whether the type of splitter would make any difference in this 
>regard. (I do know that video resolution and quality might differ). 
>Note that I am aware of various issues (eg., input lag, rise time) 
>that can compromise timing accuracy of LCD displays. As a said at 
>the outset, I'm not expecting perfection, or even anything close to 
>the accuracy of a single CRT monitor. My goal is simply to minimize 
>the variability of the time between the onset sync, detected by 
>E-Prime, and the onset of the visual display seen by the subject. A 
>constant lag does not concern me. Also, the two monitors to do NOT 
>need to be synchronized with each other, except to the extent 
>necessary for even one to be (relatively) synchronized to the 
>vertical blank. Also note that I am NOT concerned or asking about 
>synchronization between physiological recordings and the vertical 
>blank time detected by E-Prime, signaled via the parallel port; 
>that's a different and less troublesome issue, imho. Also, I 
>understand that timing accuracy is more or less critical, depending 
>on experimental paradigms and physiological measures. All I'm asking 
>about is which of the 3 methods listed above can be expected to 
>yield the most consistent and reliable (or least bad) timings, as a 
>general rule, when connecting two LCD displays, both showing the 
>same content,  to one PC running E-Prime. If anyone knows any better 
>methods, other than these 3, I'd like to hear about them as well.
>
>Thanks, in advance, for sharing relevant experience, knowledge, and 
>advice. --Scott

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