randomly choose videos to play within a video

[Melissa Abo]

Hi, I'm trying to set up a stimulus that would be a lot like watching regular TV...including commercial breaks. I have a clip of American Idol that I have edited into 3 sections to allow for 3 commercial breaks (don't worry, our Ps will get plenty of extra credit for being forced to watch American Idol!). I'd like the commercials to be chosen randomly without replacement from two pools of ads I have (target ads and filler ads). Each commerical break would have 3 commercials...2 of which were fillers and one a target ad.

In other words, Ps would watch part one of the American Idol clip and then see 3 commercials. Two of these would be fillers and one would be a target commercial. Then they'd watch part two of the American Idol clip and 3 more commercials. These would also be 2 fillers and one target, but could not be any of the commercials already viewed. Then part 3 of American Idol followed by the final 3 commercials...also 3 new commercials. So they'd watch 9 commericals in all, 6 of which were fillers and 3 target, and no commercial would be seen more than once.

Any ideas? Thanks so much for your help!
Missie

[jason_reed]

Hi Missie,

This study should be very straightforward to do in DirectRT. You should be annoying your participants with American Idol clips in no time.

The key component is to use the StimLists function in DirectRT; you can find information about all of this in the Input Files > Stim-Stimulus section of the DirectRT manual. You will want to create two .txt files, one for each set of commercials. I attached a quick example, one named filler.txt and one named target.txt for each type of commercial. Just replace each with the name of your actual commercial files, including the file extension (.wmv in this case).

I've also attached a .csv file called AIcommercials.csv. Look at the stim column. I assume that you will just play the American Idol clips in a set order, so I placed them to play before commercials in trials 1, 5, and 9. To get your desired effect of selecting commercials from each pool at random without replacement, we simply use a $ followed by the name of the StimList without the .txt file extension. For this example, two fillers come before the target. You can arrange that how you want or use the BGR and WGR fields in the .csv file to randomize the placement of the commercials.

Make sure that you put all your movies in a folder named stim, the StimLists, and the input file in the same experiment folder. Please let me know if you have any other questions and if this is what you were looking for.

Cheers!

[Melissa Abo]

Thank you; I'll try it! Maybe mine wasn't working because I was trying to fill in pixel info (I read something in the manual about writing (640x480) at the end of the file name) and also I didn't have the ".avi" at the end of the stim name in the stim list.

I'll revise and try again!

[Melissa Abo]

Hi Jason,

I'm either cursed or I have a typo or something in my file! I keep trying it, but it keeps freezing my computer. Even control-alt-delete won't work. Would you mind taking a look at the attached to see if you can tell where I went wrong?

Thank you so much; I really appreciate it!

[Melissa Abo]

huh, I can't see to do anything with computers today

[jason_reed]

Missie,

Does this work in DirectRT without trying to use MediaLab? And what versions of DirectRT and MediaLab are you working with?