meaning of ActionDelay for long audio files

[David McFarlane]

Brian,

As to reducing the latency for the onset of your sound stimuli...  I 
have just been catching up on the improvements made in EP2.0.10.182, 
and noticed the new SoundTester application, documented at 
http://www.pstnet.com/support/kb.asp?TopicID=4348 .  This may help if 
you are using EP2 under Vista/7.

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


At 2/16/2012 05:58 PM Thursday, you wrote:
>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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