GDF files not obtaining Sample Rate?
Posted: Fri Jun 23, 2017 6:51 pm
Hi all,
We've observed an issue importing GDF files converted from EEGLAB to Openvibe. This happens regardless of whether the source file is .EEG or .EDF. The 3d and 2d topographic map is generated correctly, but the Power spectrum display and time frequency map display are not showing, with no errors. We believe that this is because the GDF's sample rate isn't being read into OpenVibe correctly("sampling frequency was estimated from the chunk size to be 0... Forcing the rate to 1"), which is seen as a warning in the console picture. I've already tried the following fix, which hasn't resolved the issue (unless I did it wrong?):
“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;"
Here is the writeeeg.m, the GDF File and the scenario:
scenario: https://drive.google.com/file/d/0B1xYXD ... sp=sharing
tester gdf: https://drive.google.com/file/d/0B1xYXD ... sp=sharing
writeeg: https://drive.google.com/file/d/0B1xYXD ... sp=sharing
Thank you all in advance for your help,
Dominic Suares
We've observed an issue importing GDF files converted from EEGLAB to Openvibe. This happens regardless of whether the source file is .EEG or .EDF. The 3d and 2d topographic map is generated correctly, but the Power spectrum display and time frequency map display are not showing, with no errors. We believe that this is because the GDF's sample rate isn't being read into OpenVibe correctly("sampling frequency was estimated from the chunk size to be 0... Forcing the rate to 1"), which is seen as a warning in the console picture. I've already tried the following fix, which hasn't resolved the issue (unless I did it wrong?):
“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;"
Here is the writeeeg.m, the GDF File and the scenario:
scenario: https://drive.google.com/file/d/0B1xYXD ... sp=sharing
tester gdf: https://drive.google.com/file/d/0B1xYXD ... sp=sharing
writeeg: https://drive.google.com/file/d/0B1xYXD ... sp=sharing
Thank you all in advance for your help,
Dominic Suares