OpenViBE forum

Dear All,

I am designing a neurofeedback scenario for Alpha up training while playing some music in the background. I am using Emotiv Epoc+ headset for the raw signal. I have a couple of questions regarding the different elements of the OpenVibe designer.

I can correctly extract the alpha band and compute the alpha power using the signal display element. I want to show/visualize the alpha band power as vertical bars to the participants. Can you help me which element to use for this purpose? I added "Level measure" element from the visualization>basic box (see the screenshot attached), but it gives me the bar with respect to each electrode. I want only one bar to show mean alpha power across all electrodes. how can I do that?

Another question is that I want to control the volume of the background music using a threshold value from the alpha power. this means when the alpha power reaches a lower limit the volume of the music goes down and if the alpha power reaches to upper limit the volume increases. Is there a threshold element for this purpose?

I can see from the example scenarios, there is a spaceship example. is it possible to control the speed of the spaceship using the alpha power? for example, the speed of the spaceship increases gradually with an increase in alpha power and vice verca, and visualize it as feedback stimulation game to the participant.

I hope to get your help. Thank you

Rabnawaz

Hi!
Did you manage to find a solution for your problem?
I was wondering: which math formulas are you using inside the simple DSP boxes?

Best regards,

Bruno.

Hi,
This subject is old, not that it goes back here but I think he had to create new boxes to do what he wanted (that's what I did in my case). Regarding the simple DSP boxes the first contains just the formula "x*x" and the second probably "log(1+x)" it's common when you wan't the energy of the signal in one spectral band.

Thibaut, thank you for your answer!
By the way, could you tell me what does the reference Channel is supposed to be?
I am asking this because the reference channels of my EPOC+ are (supposed to be, at least) the P3 and P4 channels... however, I am not able to access them through openvibe, since I am using the Cykit 3.0 and it does not provides these 2 channels when interfacing between the OpenVibe software...

Hi,
The reference channel is normally one that will divide (or subtract or else I do not remember) your signal. Some cap no longer need this box because the amplifier is responsible for removing the reference. Normally the doc of your cap tells you if there is a reference channel or if it is managed automatically
Thibaut