OpenViBE forum

Hello,

I am new to OpenVibe, so I am still trying to familiarize myself with the boxes and how they work. My question is, I have gdf file on hand that involves a subject imagining certain hand movements- this file is compatible with OpenVibe, as I have been able to open it using the GDF file reader box. I know that the handball application is included with openvibe, but how would I use it with the offline GDF file I have?

My goal is this: to train the Handball application, just like in the video (when the user is seen wagging his hands) using the motor imagery file I have. Then, I plan to "play" the file back to the handball app and analyze the accuracy with which it recognizes the imagery pattern.

If anybody could provide details on this, that would be great, because I am still new to OpenVibe's interface.
Thanks


--edit--

Also, I'm trying to start using the handball application with some of the sample eeg data provided with openvibe, but I don't know where to begin. I know there are 4 files in the "motor imagery" directory in OpenVibe/Share/, but I am not sure where to start using these files- even if my above question cannot be anwered, I would really appreciate it if anyone can provide information on how to start using the handball application itself. I'm not able to make much sense of the tutorials but would appreciate a "starting point" of some sort.

Dear asrinivasan,

did you record the files using the motor imagery bcis that come with OpenViBE ?

Yann

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Hi yrenard,

Using the 4 motor imagery files that are provided with openvibe, I'm essentially trying to replace the acquisition client with a GDF file reader box that opens the "real-hand-movements" file that comes with openvibe. I have attached two screenshots showing this.

Currently, I'm using the "motor-imagery-bci-3-online.xml" file to simulate online use using the GDF file reader. At the end of the scenario, where there is a classifier processor box(as you'll see in the screenshots), I'm using the config file "openvibe/share/openvibe-scenarios/bci/motor-imagery/motor-imagery-bci-config-classifier.cfg". Is this correct?

Also, whenever I try to run any of the motor imagery files (1-4), there is always an error message in the log saying how a certain file was not found or the GDF stream writer failed. Log is attached.

In other words:
I'm trying to re-create the motor imagery scenario as seen in the last part of the video tutorial, but I'm trying to replace the online acquisition server with a GDF file reader box. If you could explain to me how I would go about doing this and why the log is giving me these error messages, that would be great.

--edit---

I switched to a different computer (XP), and this time it worked- I have a feeling this had to do with the administrator privileges in Windows 7. Now I am able to run the motor imagery 3 scenario using the configuration file that was produced earlier. In the graz visualisation I am able to see the left/right arrows and then the corresponding thought process indicated by a blue bar.

My need now is, to analyze the accuracy with which OpenVibe recognized the signal patterns based on the config file. I wish to do this by having OpenVibe type a specific letter when the blue bar in the Graz visualisation reaches a certain threshold (either on the left or right side of the coordinate plane). Is this possible?

Thank you for your time

Hi asrinivasan,

I'm glad you got it working !



The second output of the classifier processor box is a Streamed Matrix that contains a value, whose sign gives you the side and absolute value gives you the amplitude of the blue bar. This value is the distance to hyperplan computed by the LDA classifier. As stated in the box documentation :

We don't provide in openvibe a way to emulate the keyboard. However it is possible to send stimulation codes or analog values in a VRPN server, that a third party application could read and "type" a specific letter depending on the VRPN input. Anyway, I'm afraid you will have to implement something

hope this helps,

Laurent-

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