TTL insertaion

[mickeyi]

I'm trying to create a movie and then have a TTL signal be sent at a specific moment during the movie (e.g. when the filmed person says "welcome"). Is there any way I can embed a TTL in a movie? If not, perhaps I can create the movie so that I would want the TTL sent at a specific time (say at 10s after the movie begins). Is there any way a TTL can be sent after a specified period of time?

Thanks!

[jarvis24]

No. But you could send one at the onset of the movie and have it stop at a specified period of time--would that work for you? If so, just send the TTL signal before the movie and specify the duration in milliseconds. The movie will start in synch with the signal and the value at the port address will return to its pre-movie state after the specified time elapses.

[mickeyi]

Unfortunately that won't work. We use TTLs for an EEG system and my EEG hardware only recognizes the start of a TTL... Is there any way to "hardcode" a TTL into a movie? Any other way around this? I imagine this could be useful for people who do work with psychophysiology and want to "time-lock" the response to a specific event in a movie.

[jarvis24]

Actually, it just occurred to me that you could do this the way you want. Show the movie with a time value of 0ms. THEN insert a blank stimulus "~" with a LOC value of "0,0,0" with a time value that corresponds to when you want the TTL signal to occur. THEN send the TTL signal. I think that ought to do it.

[mickeyi]

OK. Let me see if I understand the logic. Let's say I want to show a 15 second movie, and I want a TTL sent at 9.8 seconds. To do this I would show the movie with a time of 0, and then send an empty stim with a time value of 9800 (the movie will still show because we didn't clear the previous screen, right?), ans then send a TTL at port 888 for say 5ms. Is this right? Also, will the movie play till the end of the 15 ms?

Thanks!

[jarvis24]

Yes, I expect that is how it would play out.