OpenViBE forum

Hi, glad to find here and urgent to ask one question.
We have developed an EEG amplifier---in its primitive stage though.
It works fine with the Modular EEG P2 driver because we used their proxy.
And if we send 6 channels of ideal sin waves to test, the perfect waves could be received via the serial port and displayed on openvibe.

When we run the motor-imagery-bci-1-acquisition xml, the tagging just looked very dense and weird, almost ten times one second.
But if we changed the acquisition server to general oscillator or general time signal whatever built-in signal generators, the tagging was fine.

BTW, we also recorded the signal and stimuli tagging together into CSV files, the built in signal generator files have very few tagging in the CSV file,
however the ov file can be correctly read out with the General file reader, including the tagging. It can also be correctly transferred with the ov2mat function into mat files.

Our amplifier produced CSV file has a lot tagging in the CSV file, but cannot be read out by the ov2mat function. This ov2mat could not seperate the stimuli information.

I am very very confused.

Thanks a lot !

We found that when doing acquisition only , there are periodic tagging.
Here posted two figures, hope they would appear normally.

I found the stimuli list.

OVTK_StimulationId_AddedSamplesBegin OVTK_StimulationId_AddedSamplesBegin 0x00008311
OVTK_StimulationId_AddedSamplesEnd OVTK_StimulationId_AddedSamplesEnd 0x00008312

It seems we are receiving these stimuli repeatedly, almost 25 Hz, when doing acquisition.
Could anyone possibly tell me where it went wrong?

A lot of thx!

Hi,
For me nothing is wrong here. Your acquisition send stimulus at 25Hz.... The driver (or proxy in your case if I understand) send this stimulus. It's not a problem it's not obligatory to save this. If your signal is good there is no problem.
Thibaut

Thanks for your reply.
We also found out these tagging do not interfere with motor imagery tagging.
However, I still wonder where do these tagging come from?
We used the driver OpenEEGModularEEG, and did not modify it.
If you could tell me which lines are for these tagging I will be very appreciated， thx a lot!

Hi have dig a little.
This stimulus is send when you have a correction drift (acquisition server preference)
Thibaut

Thx, I got it.
One thing I want to say is that I did a little modification to the stimulation also.
But found out when configure sound player settings, the PLAY trigger should be OVTK_GDF_right or OVTK_GDF_left.
Yet in the stimulation list it is OVTK_GDF_Right or OVTK_GDF_Left.

Maybe someone else would get confused with this little difference.

Best regards and thx !