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Thread: Direct RT V2008 lagging speeds to display stimuli (case 16596)

  1. #1

    Direct RT V2008 lagging speeds to display stimuli (case 16596)

    I am trying to run an abbrevaited vigilance test which requires pulling in 2 images every 40 miliseconds for 6 - 2 minute intervals.
    Ther problem is that there seems to be a time lag during the test and the images do not flash on the screen every 40 milliseconds. We initially tried bitmap files, then jpegs and then tried 16 bit bitmap files ( 500 Kb) but a 2 minute test is taking 2 minutes and 6 seconds which is giving extra time during the test to the participants which ultimately makes the test less challenging than it should be.

    Have you any suggestions as what can be done to remove the time lag for these images?
    Last edited by jason_reed; 10-10-2014 at 11:09 AM.

  2. #2
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    Could you please upload a copy of your .csv input file and the short and long (i.e. log) output files it produced? I would like to take a look at them to see exactly how the timing breaks down for each stimulus and trial.
    Jason Reed
    Empirisoft Software Support Specialist

  3. #3

    AVT csv files

    Hi,
    I have attached the csv and log files. Let me know if you need anything else. There are two more images (o and D which are also 500kb files) which would not upload as they are too big

    Thanks
    Fiona



    Quote Originally Posted by jason_reed View Post
    Could you please upload a copy of your .csv input file and the short and long (i.e. log) output files it produced? I would like to take a look at them to see exactly how the timing breaks down for each stimulus and trial.
    Attached Images Attached Images
    Attached Files Attached Files
    Last edited by fiona wixted; 10-13-2014 at 07:53 AM.

  4. #4

    Additional images for required for AVT test

    I have attached two more images (o and D) here that I'm using to run the AVT test.

    Thanks
    Fiona
    Attached Images Attached Images
    • File Type: bmp D.bmp (500.1 KB, 2 views)
    • File Type: bmp O.bmp (500.1 KB, 1 views)

  5. #5
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    Could you please also upload a copy of the styles.drt file you use?
    Jason Reed
    Empirisoft Software Support Specialist

  6. #6
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    Please also tell me the screen refresh rate options you have for your monitor. You can find instructions for your Windows OS here: http://www.microcentertech.com/tech_...OW8003892B.htm. Please be sure to tell me all the options in the dropdown menu as well as the one you used when you actually ran your DirectRT files.
    Jason Reed
    Empirisoft Software Support Specialist

  7. #7

    Refresh rate

    Hi,

    My refresh rate options for True Colour are 60 Hz or 75 Hz but I have tried varying the refresh rate and it hasn't had an impact on the test timing. I have attached the styles.drt form. The refresh rate was set at 60 Hz when I ran the test initially. Any ideas on what I could try to reduce the lag time?

    Thanks a million,

    Fiona
    Attached Files Attached Files
    Last edited by fiona wixted; 10-16-2014 at 06:39 AM.

  8. #8
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    After taking a look at all the files, I have some thoughts on two aspects of your project.

    First, there's the point about presenting two images (i.e., a letter.bmp file and the blank.bmp file) at the same time for a specific amount of time (i.e., 40ms). As discussed in the DirectRT manual section about screen refresh rates (http://www.empirisoft.com/directrt/h...y_concepts.htm) DirectRT " will display your stimulus for as many screen refreshes as it takes to come closest to your requested display time and will create a log data file for you so that you can compare requested against actual presentation times." So your ms per refresh would have to be a divisor of the desired display time; in your case, the ms per refresh would need to be something like 20 ms per refresh for your desired 40 ms display time. One thing you can do is to check the ms per refresh (1000/screen refresh rate) for different screen resolutions to see if the meet this criteria. Otherwise, DirectRT will do its best to display stimuli for the requested number of ms in the input file based on the screen refresh rate.


    Second, there is your desire to have the six two-minute intervals; I assume this corresponds to trials 2-7 in your Fiona Script.csv file. You could control this by using a style code in the style column of the Fiona Script.csv file that has 0-120000! to stop each row of it after 2 minutes pass from the time the first stimulus in each row of your input file is presented. You can also use a different style code between <> to keep the automatically moviing on to the next stimulus for your keypresses like it describes here in the DirectRT manual here: http://www.empirisoft.com/directrt/h...ctrt_style.htm. See the attached styles file and Fiona script styles.csv file for an example.


    Alternatively, you could use the meta column feature (see http://www.empirisoft.com/directrt/h...a_commands.htm) to create the same 2 minute time limit for each of row of your input file. Take a look at the attached Fiona script meta.csv file for an example that tells DirectRT to move on to the next trial after 2 minutes has passed. As with the styles code option, this should move on 2 minutes after each row of your input file starts regardless of whether the participant has progressed through everything in each row of the trial.
    Attached Files Attached Files
    Jason Reed
    Empirisoft Software Support Specialist

  9. #9
    Thank-you for your help. I will implement your suggestions.

    Fiona

  10. #10
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    You're welcome. Let me know what happens.
    Jason Reed
    Empirisoft Software Support Specialist

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