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PostPosted: Thu May 26, 2011 1:41 am 
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Joined: Sat Jan 15, 2011 7:25 pm
Posts: 6
Hi Guys,

A couple of questions...

First Question:I'm trying to write a GDF in OpenVibe and I keep getting the following error and the application will not write a GDF file.

[WARNING] Box algorithm <GDF file writer> has been deactivated because initializ
ation phase returned bad status
[WARNING] At time 97542733824 (0x16b6000000)<Box algorithm::GDF file writer> Err
or while writing to the output file!


What am I doing wrong here................

Second Question: I would like to read this GDF file using EEGlab, but I have heard from others that:

Openvibe apparently manages GDF files in version V1.25. If you export EEG data from EEGLAB in a GDF file, this will be created using the gdf 2.11 version, which is not readable by Openvibe (you get the warning message indicating the presence of channels with different sampling rates). As a simple workaround, just modify the script writeeeg.m of EEGLAB like following :

HDR.VERSION = 2.11; ==> HDR.VERSION = 1.25;


EEGLAB will then create gdf files readable by Openvibe.

This is fine if you are looking at data in EEGlab and want to bring it to OpenVibe.

But is there anyway of doing the opposite converting Openvibe GDF version 1.25 that will open in EEGlab gdf v2.11. Has anyone written a convertor, or how do I do it?


The Final Question: I am planning to use the Emotiv Epoch EEG with the motor sensory BCI. And I am interested at exploring areas around C3 and C4 that are not covered using the sensors in the regular frontal placement using the EEG device. The sensors only cover areas AF3, AF4,F7,F8, F3,F4,FC5,FC6,T7,T8,P7,P8,O1,O2.

Which completely misses the motor sensory cortex, which surround sensors C3, FC4, C5, C6,C3,C4,C1,C2,CP3,CP4.

If I reverse the emotive headset I get the following sensors AF7,AF8,FT7,FT8,C5,C6,CP5,CP4,CP3,CP4,P3,P4.

In this reversed position I am closer to the peripherals of the sensorimotor cortex and the spatial and temporal resolution will obviously be better exploring the following sensors C5, C6, CP3, CP4.

How can I modify the Emotiv Epoch driver to account for these reversed sensor positions?

Thanks a million :?:

Tiernan


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PostPosted: Thu May 26, 2011 4:00 am 
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Joined: Sat Jan 15, 2011 7:25 pm
Posts: 6
The answer for the question related to the reversal of the sensors and sensor locations, I have just figured out.

Download version 0.10.1 and change settings in Driver properties? But I have done this and now the original driver wrote for the last version 0.9 doesnt work....Any suggestions greatly appreciated...

Tiernan :?


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PostPosted: Thu May 26, 2011 8:48 am 
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Joined: Tue Nov 02, 2010 8:51 am
Posts: 239
Location: Mensia Technologies Paris FR
Hello Tiernan

I answered your third question here : viewtopic.php?f=4&t=485

For the GDF :

In your first question I would need to see the scenario you have used, at least the configuration of the GDF writer box. As a wild guess I would say that you do not have permissions to write to the location you have specified. By default OpenViBE installs itself to Program Files folder and writes files to its dist/share/openvibe-scenarios/signals/ folder. On 64bit windows 7 this folder is not (and can not be) user writable.

As for the conversion between 1.25 and 2.11 it is not possible in OpenViBE.

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PostPosted: Fri May 27, 2011 9:08 am 
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As far as I knew, OpenViBE gdf files can be opened in EEG lab, not the opposite.
Yann

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