Timing issues

[Kam]

Hi all,
I'll try to be as brief as possible. I've already read CH 3 of the
user's guide re: timing in e-prime. My question concerns why nothing
to very little of the timing data output in my edat file makes sense
in the context of CH 3.

The experiment is a simple random presentation of sound files of
moderately varying lengths, separated by a random interstimulus
interval. The set-up includes a trial procedure with an inline that
among other things defines a variable SOA set to 100 (for testing
purposes) and the command c.SetAttrib "ISI", SOA to set ISI duration.
Then the trial procedure proceeds with a (1) SoundOutObject called
Stimulus with attributes {buffer size=800ms; buffer mode=streaming;
start/stop offsets=0; loop=no; stop after=yes; end sound action=none;
duration=800; timing mode=event; pre-release=0; sync onset/
offset=none} and (2) pause command called ISI with attributes
{duration=ISI (mentioned above); timing mode=event; pre-release=200;
sync onset/offset=none}. Subsequently the trial procedure terminates
having cycled through a stimulus list and the experiment concludes in
a single Block List. So that is 3 hierarchical procedure levels in all
{session, block, trial} with only 1 block of stimuli.

In my data file what I can make sense of is:
(1) Stimulus.Durations = 800 as defined in the Stimulus attributes
(2) Stimulus.OnsetTime = Stimulus.Start time and occurs before (3)
Stimulus.OffsetTime = Stimulus.FinishTime
(4) Stimulus.DurationError = 0 considering Onset and Offset times
occurred as expected
(5) ISI.Duration = 100 as defined in my inline


And what I cannot make sense of; I would appreciate if anyone can help
me resolve:
(1) There is a cyclical "drift" when I plot Stimulus.OnsetDelay
irrespective of where I use a pre-release (ie., 100-200 msec in either
the Stimulus or ISI-wait objects)
(2) ISI.OnsetTime = ISI.Start time = ISI.OffsetTime = ISI.FinishTime
(3) ISI.DurationError = 100

Generally speaking, there is very little said about proper
implementation of the SoundOut object, and the entire timing
discussion revolves around display refresh rates, which I don't
understand the importance of in a strictly auditory set up. Also, does
anyone know the exact web address where I can download the critical
timing eprime scripts mentioned in the user's guide?

Thanks in advance
Kam

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