By Timmojh - 6/9/2014
Hello, I'm new to the Inquisit universe so apologies if this has been asked previously!
I'm looking to overlay stimuli (e.g. images, shapes) over a playing video at set intervals during a trial. However, I'm not able to make this happen currently, not sure if anyone has any experience of this or if it is possible?
Ultimately I would like to run something like the Pursuit Rotor Task over the top of a video, but think this may be a bit optimistic for the time being?!
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By Dave - 6/9/2014
You cannot easily overlay <text>, <picture> or <shape> on top of a video. Think about it: A video is moving pictures, i.e., the screen portion displaying the video has to be redrawn all the time. Any static stimulus (e.g. <text>) you draw in this region will be visible for a single frame only. Two options:
#1: You either need to redraw your static stimuli every frame (which may not be possible to do depending on other aspects of your procedure).
/ stimulusframes = [1=myvideo; 2-1000=mytext]
#2: You *can* overlay other <video>s on top of each other. So, instead of using a <shape> or <picture>, prepare videos of your stims and properly set up <video> elements for them.
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By Timmojh - 6/19/2014
Thanks Dave,
Does make sense now you mention it!
Just on the topic of drawing static stimuli, how does Inquisit decide on the order of presentation? For example, if I have 3 elements "A", "B" & "C" which have a degree of overlap and drawn on the same frame (e.g. /stimulusframes = [1=A,B,C]) which will come out on top ? - Realise I can just try this for myself, but I'm away from my computer at the moment!
Also, Inquisit handles different video formats, is there any it generally works better with?
Tim |
By Dave - 6/19/2014
They are drawn in the order given, left to right. Here A first (bottom), then B (middle), then C (top).
As for video formats it depends on the systems you are aiming at. For Windows, WMV is a pretty safe bet. For maximum cross-platform compatibility, you'll want to pick something like an MPG2 codec. You'll find this covered in the documentation for the <video> element.
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