[DMDX] RE: Re: output latency Thanks for the help, guys.  I've tested the latency of the sound card before, and it has been fairly small and stable.  I will check it again today to make sure.   I've altered the script to include the  keyword:   1          o1  "1050" /   "wnprobe"  o96 /;   As I understand the documentation, this current configuration would mean that "wnprobe" will start playing when 96 is output, as is desired.  Is this a correct reading?   Ian     _____   From: DMDX-owner@psy1.psych.arizona.edu [mailto:DMDX-owner@psy1.psych.arizona.edu] On Behalf Of John Curtin Sent: Thursday, October 06, 2005 6:35 AM To: DMDX@psy1.psych.arizona.edu Subject: [DMDX] Re: output latency   Ian, I am assuming that you are measuring startle.  The svp start that Jonathan indicated will synch up the request to play the sound with the output. However, you should also  know that in our testing, sound cards varied quite dramatically in how long the delay was between that request and the actual start of the sound (in your case the noise probe).  Perhaps more troubling, for some cards, that delay was not only long, but quite variable trial to trial ( e.g., range from 4 - 20 ms for one card), which would really screw up your ability to measure startle latency if you care about it (and your ability to average startle waveforms if you reduce startle that way).  You can test this most easily for you card by sending the output of your sound card to an analog channel on your physio amplifiers and verifying its onset relative to the trigger code you are outputting.  Hope that helps.    J   On 10/5/05, Ian Mathis  wrote:  Hi list. I have a question about the timing of outputs in a frame. I am presenting white noise probes of 50 ms duration and sending a  corresponding trigger code to the data acquisition computer using DMDX.  The measured latencies of the physiological responses we are getting don't really make sense, and I am trying to figure out what's going on.  Here is a line that presents the probe and sends the output: 2          o8  "6510" /  o96  "wnprobe"/; As far as I can tell, the output of "96" is sent at the onset of the wav  "wnprobe."  Is this correct? Our data seems to imply that the output might be coming after the probe is played, but that doesn't make sense to me. Thanks for your help. Ian Kristopher Ian Mathis, M.A. Graduate Student, Clinical Psychology Dept. of Psychology, UCLA ====================================================================   Send mail to DMDX-request@psy1.psych.arizona.edu with the word 'unsubscribe' by itself with no quotes in the body of the email to be removed from the list.  The list archive is available here:          http://psy1.psych.arizona.edu/cgi-bin/DMDX/thread ==================================================================== --  John J. Curtin, Ph.D.  Assistant Professor of Psychology  University of Wisconsin  1202 West Johnson St.  Madison, WI 53706  Email: jjcurtin@wisc.edu  Website: http://dionysus.psych.wisc.edu    Office: 608-262-0387  Lab: 608-262-5621  Cell: 608-217-6221  Fax: 608-262-4029