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jim.voyvodic
BIAC Faculty
138 Posts |
 Posted - Apr 19 2005 : 08:59:46 AM
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We discovered and hopefully fixed a problem in CIGAL that caused sound stimuli to be delayed during real-time paradigms. Apparently Windows XP handles process priorities differently than earlier Windows systems, such that sound events have lower priority than other window events. By default CIGAL is set to switch to high-priority mode when it runs a real-time paradigm (to prevent other users or processes from interfering with your paradigm). But only some events appear to be treated as high priority, and the operating system puts off actually doing what it considers low-priority tasks (like playing a sound) until there's nothing else going on.
The fix in CIGAL is simple. Setting the paradigm control flag (PDFLG) bit 2048 (04000o) prevents CIGAL from trying to run at high-priority. I have made this the default on Gall:\Programs as of this morning and will do the same at the 4T scanner later today.
This should not make any difference for CIGAL paradigms that only use video, but probably will affect the timing of sound stimuli. If you have been using sound stimuli in CIGAL on Windows XP before now, please test your paradigms to see if the task timing has changed. (Try running a paradigm twice, once with the line "pdflg = 4000o" and once with "pdflg = 0" in the parameter portion of the PPF stimulus file.)
Jim |
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XP bug fix in CIGAL
