Home Questions How do I ensure consistent delays in visual stimuli when sharing tasks with another lab or changing my subject display model or refresh rate?

How do I ensure consistent delays in visual stimuli when sharing tasks with another lab or changing my subject display model or refresh rate?

DWQA QuestionsCategory: Custom Task DevelopmentHow do I ensure consistent delays in visual stimuli when sharing tasks with another lab or changing my subject display model or refresh rate?
Ian Brown Staff asked 4 years ago
If I share my task with another Kinarm lab, whose subject display monitor has different latency properties compared to mine, 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?
1 Answers
Ian Brown Staff answered 4 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.