Ian Brown Staff asked 6 years ago
If I share my task with another Kinarm lab, whose subject display monitor has different latency properties compared to mine (for example, one lab uses a 120 Hz monitor and another lab uses a 60 Hz monitor), then it is possible that the delays in presentation of visual stimuli might be different?
This same scenario can happen within my own lab, if I replace my subject display, or if I change the refresh rate.
Are there any tools to help manage this problem?
Ian Brown Staff answered 6 years ago
Starting in Dexterit-E 3.7, the Task Development Kit (TDK) provides a method of aligning delays of visual stimuli between two different systems. Older versions of Dexterit-E cannot take advantage of this feature. In the TDK, the Process_Video_CMD block has a parameter that you can set which will add delays to faster video systems to ensure that they match slower ones (i.e. to ensure that there is a consistent delay in visual stimuli for different video systems). The HELP for the Process_Video_CMD block describes this feature and how to use it.
It is important to note that this approach is only going to be as accurate as the feed-forward delays used in Dexterit-E for the different displays. If you need ~1 ms accuracy, then you will want/need to use a photodiode to calibrate, and consider possible implications of different rise-times on different displays (which is not explicitly handled by this solution). If your needs are for 5-10 ms accuracy, then you should be able to use this approach with our suggested values for the feed-forward delays.
You can read more about subject display latencies in the section "Understanding Subject Display Latencies" in the Dexterit-E User Guide.
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