Timing issue - movie / sound

[David McFarlane]

Soizic,

The Knowledge Base at the PST website has some information about this 
issue.  But ultimitely, you need to use some external calibrating 
equipment (e.g., oscilloscope, or Black Box Toolkit 
(http://www.blackboxtoolkit.com )) to measure this all for 
yourself.  E.g., put a photosensor on your display device, a 
microphone up to your sound device, and measure the actual delays for 
your equipment.

The PST website has some advice on how to minimize sound latency in 
general.  You also want to minimize the latency between movie onset 
and sound onset, for that you should use a Slide to start the movie 
and sound at the same time.

Now, if you merely want to add some synchronizing signals for your 
video and physiological recordings, then you might try another 
approach.  In particular, use WritePort, OnsetSignal..., or Task 
Events to operate a low-latency digital signal through something like 
a parallel port, and pipe that directly into your electrophysiology 
or video -- if need be, use that signal to operate the flashing of an 
LED to record on the video, etc.  You should be able to think of something.

-----
David McFarlane
E-Prime training 
online:  http://psychology.msu.edu/Workshops_Courses/eprime.aspx
Twitter:  @EPrimeMaster (https://twitter.com/EPrimeMaster)

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At 8/5/2013 07:50 AM Monday, Soizic Argaud wrote:
>For my experiment, I present on the screen (full screen) short 
>movies without sound. Because I film the participants during the 
>experiment and work on the video files obtained (I am obviously 
>interested on the moment when they see the movies), I add a sound on 
>the same slide where short movies are and record this sound on the video files.
>
>I wonder if there is a kind of time gap between the "presentations" 
>of the sounds and those of the movies in E-Prime ?
>
>In the same time, I record electrophysiological signals from the 
>participants. I use E-Prime to send triggers on this recordings 
>allowing me to target the apparition of the short movie and I also 
>record the sound on an other channel (in this way, I can consider 
>the sound like "sound trigger" which should correspond to the E-Prime trigger).
>
>I see on this biological recording that there is a difference of 
>nearly 50 ms between the E-Prime trigger and the "sound" one whereas 
>the E-Prime trigger should correspond to the apparition of the slide 
>where there are both the short movie and the sound.
>
>Is it possible to have a better timing in this configuration ?
>
>I hope I am clear enough...
>Thank you so much if you can bring me an answer about that,
>
>Best,
>Soizic

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