TTL insertaion

[mickeyi]

That's really too bad...

Is there any way this option can be programmed in? I realize this is a difficult problem, so another option is that I can pay for Empirisoft's programming services to program this extra functionality into DRT. Is this possible? I REALLY want to do this project...

[mickeyi]

Hi-- I think I have finally found a way to make this work, but I need to verify that DRT can handle this accurately. The first step is to get the exact time I need the TTL to be inserted in the movie, starting from the movie onset. Once I know this time, I can manually add a trigger code into my EEG program. So, for example, if I need a TTL of "101" at 5.987 after the onset of a specific movie with TTL code "100," I will simply add this TTL whenever I see a trigger code of 100. I think this is straightforward. The only way to make this work, though, is if I know the TTL that is sent at the onset of the movie (something I can now do with DRT) is accurately timed. That is, this solution will be screwed up if, for example, the TTL is sent and then the movie plays after a few hundred milliseconds because of processing delays. Can you please confirm that a TTL set at the onset of an .avi file will indeed be sent at time 0 of the movie. Do I need to make sure the movie is under a certain file size to ensure this will happen?

[jvanbavel]

I have a related problem using DirectRT 2006. I plan to show a series of 15,000ms videos. On each trial, participants will have to make a response at some point during the middle of the video. However, I want the video to play for the full 15,000ms. I am looking to have two TTLs sent for each trial. I want one TTL sent when the video starts and another TTL when participants' make their response. In other words, I want to examine the data when the video starts (i.e., stimulus locked) and when participants make a response (i.e., response locked).

Is there a work-around when the response in the video is not fixed?

[jarvis24]

First, Mickeyi--yes, you should be able to count on the ttl signal and the movie signal being sent out simultaneously at the onset of the video--i.e., with no lag due to processing/loading of the video clip.

Second, Jvanbavel, your second question regarding whether you could get a ttl signal to accompany the subject's response at some point *during* the movie can be answered, yes. Details are here:

http://www.empirisoft.com/Support/showthread.php?t=273

See in particular the sections on echoing ttl signals (revisions 2008.1.13 and 2008.1.18). Mickeyi helped us with the development of that feature so he may have some info to help you on this also if you need it.