meaning of ActionDelay for long audio files

[David McFarlane]

Brian,

I have tried to untangle this myself, and you can see the result at 
http://groups.google.com/group/e-prime/browse_thread/thread/39e899d3457d4917 
.  In my tests, I was never able to get ActionTime to lag more than 1 
ms behind OnsetTime, so your report does add something to the 
discussion.  Based on that, I would guess that OnsetTime means, 
vaguely, when E-Prime first submitted the stimulus data for 
presentation (e.g., proceeded to copy data to display memory or load 
a sound buffer), whereas ActionTime means when E-Prime completed this 
action (e.g., copying data to display memory, or loading a sound or 
video buffer).

Bear in mind after all this that E-Prime indicates only when it has 
made the information available to the hardware, the hardware itself 
may impose additional delays beyond the purview of E-Prime.  On top 
of all that, EP2 has had problems playing sound & video under Windows 
Vista/7, in case that applies to you, although they may have fixed 
that in the latest release (EP2.0.10.182).  Finally, if you really 
want to know when a stimulus appears relative to other events in your 
task, you will need to break out an oscilloscope.

Anyway, for a more definitive answer, you should submit this issue to 
PST Web Support at 
http://support.pstnet.com/e%2Dprime/support/login.asp (note that I do 
not work for PST), and point them to this very thread -- they strive 
to respond to all requests there in 24-48 hours.  Or try them at 
their Facebook page 
(http://www.facebook.com/pages/Psychology-Software-Tools-Inc/241802160683 
).  And then please post back here with their response so that we can 
all learn.

-- David McFarlane, E-Prime Instructor
    http://psychology.msu.edu/Workshops_Courses/eprime.aspx


At 2/15/2012 09:06 PM Wednesday, you wrote:
>I've been running a MEG audio-book listening experiment. There are
>several large audio files, each 8-12mins long. Unsurprisingly there
>are big OnsetDelays in getting these files ready to play, of the order
>of 1s. But in addition to that, for the first of the trials there is
>also an ActionDelay, of about 350ms (typically - running the
>experiment repeatedly I find that it ranges from about 200ms to
>900ms). On later trials the ActionDelay is 0ms, or occasionally 1ms.
>
>What does this mean? When does the audio track start playing? At
>OnsetTime or ActionTime? The user guide says that OnsetTime is when
>the stimulus "actually" begins, but closer reading of the Reference
>Guide suggests that it might be when *writing of the stimulus to the
>output device begins*. The ActionTime should be when the "critical
>action" finishes. What is the critical action when we're talking about
>sending audio data to the sound card?
>
>thanks,
>
>Brian

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