OpenViBE forum

Hi all,

I experienced some trouble with the GDF file writer after having used the decimation or channel selection boxes. The file is well created, but apparently, the header is not updated with the new values of parameters like number of channels or sampling frequency. This causes trouble when reading this file in other softwares like EEGLAB, for instance.

Could these parameters be updated automatically in the future, before writing the gdf file ? Or does anybody have a simple solution to this ?

Thanks in advance,

TPAC

Hi TPAC !

I tried to reproduce your problem, without success.
I tried a simple scenario :
- a GDF file reader
- a signal decimation box (factor 2)
- a GDF file writer.

When I read in another openvibe scenario the 2 GDF files (the source and the decimated one) I do have different sampling frequencies (512 and 256 Hz in my case.)
I tried the same with a channel rename and a channel selector, it worked well.

Is it happening only when trying to read "modified" GDF data in other software (e.g. EEGlab) or is it also happening in openvibe ?

Laurent

Dear TPAC,

maybe you could send a sample scenario of what you are trying to achieve.

Yann

Yes actually it happens with EEGLAB, which works (via Biosig) with GDF files version 2.11, whereas Openvibe manages GDF files version 1.25. The problem I was mentioning is that after decimation or channel selection, the gdf file header (at least seen by EEGLAB) is not modified... one can of course live with this by manually changing these values in EEGLAB...

Regards,

TPAC

Dear TPAC,

I actually hope that someone will contribute a BioSig integration in OpenViBE one day. It would solve many problems users are facing with GDF files I guess.

Best regards,
Yann