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Track flashing rate of multiple LEDs? (Read 1295 times)
softhook
Track flashing rate of multiple LEDs?
Nov 15th, 2009, 9:21am  
Hi there,

I am trying how to determine the flashing rate of multiple red LED's using a webcam. I am not that used to video tracking.

Could somebody recommend a method to start to build this?
Which video library would you use?
How would you go about tracking and recording the flashing rate of the individual LEDs?

Thanks for any ideas.

Best,
Christian
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Cedric
Re: Track flashing rate of multiple LEDs?
Reply #1 - Nov 15th, 2009, 2:00pm  
is there anything else in the image? people? movement? changing light? or is it just the LED? it depends on how the image looks what would be the best way. could you support an image, maybe we can come up with a more concret idea/solution.
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softhook
Re: Track flashing rate of multiple LEDs?
Reply #2 - Nov 15th, 2009, 4:28pm  
Hi Cedric,
Thanks for the questions!

Basically I imagine the context to be a fairly dark room with multiple people standing around or slowly moving around. On their chest is a device with a flashing LED that indicates their emotional arousal. The faster the flashing the higher the arousal. I would like to be able to track the LEDs (or people) and give them numerical feedback on the flashing rate.

if anybody has any ideas I would be very grateful!
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Cedric
Re: Track flashing rate of multiple LEDs?
Reply #3 - Nov 15th, 2009, 10:35pm  
i would say, but i dont have alot of knowledge in this field, this will be a hard task to do. So you have a changing number of moving leds and wants to track the flashing rate of every single one.
with one led it wont be to hard, it could also move. with serveral Leds not moving either, but in this case. you need some tracking that can create some kind of IDs for every detected moving object but also dont lose it as soon as it fades, therefore is not seen.
I can believe that existing tracking or detection methods or not able to do that. But maybe there are other people with more experience who come up with an solution.
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softhook
Re: Track flashing rate of multiple LEDs?
Reply #4 - Nov 16th, 2009, 2:16am  
Thanks for your thoughts Cedric! I realise that this is tricky Smiley

If I was to start with one red flashing LED how would you go about tracking the flashing rate of that one? Which video tracking library would you use?

Any thoughts anybody?

Thanks!
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Cedric
Re: Track flashing rate of multiple LEDs?
Reply #5 - Nov 16th, 2009, 3:48am  
As you mentioned that the rest of the room is dark, i would say you can use any blob detection library and test what works best. i probably wouldnt check for color as the bright LED maybe tends to be more white than red. So check for contrast but thats what these librarys do.
One example would be
http://ubaa.net/shared/processing/opencv/index.html there is this blob detection : http://ubaa.net/shared/processing/opencv/index.html

you can adjust the source image using contrast http://ubaa.net/shared/processing/opencv/opencv_contrast.html
and that should give you a really good source image with a black room and a white point to track.

another library is http://s373.net/code/flob/flob.html
or http://www.v3ga.net/processing/BlobDetection/

i cant tell you the differences. You just have to find out what works best.
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softhook
Re: Track flashing rate of multiple LEDs?
Reply #6 - Nov 16th, 2009, 6:25am  
Thanks again Cedric!

Does anybody else have any thoughts about which library might work best for this purpose?

Cheers
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Cedric
Re: Track flashing rate of multiple LEDs?
Reply #7 - Nov 16th, 2009, 11:13am  
another thought that came to my mind. If the red LED light is hard to track. infrared always works great if you use a webcam that that can see it.  If you dont have one, most webcams can be hacked to do so, as it is just a filter that filters out the infrared light.
http://createdigitalmotion.com/2009/08/06/trick-out-your-ps3-eye-webcam-best-cam-for-vision-augmented-reality/#more-4201
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