[FieldTrip] difference in raw time sample values for .fif files read by fieldtrip vs mne-python

Baptiste Gauthier gauthierb.ens at gmail.com
Tue Sep 16 14:27:15 CEST 2014

Dear fieldtrippers,

I recently observed that reading a raw neuromag .fif file with fieldtrip
and mne-python (with default settings for both) give exactly the same
events separated by the same time (which is good!) but with a different
time offset: the zero-point definition for the recording differ between the
two softwares. I hypothesize that this difference comes from the convention
adopted: fieldtrip would use the "record raw" trigger as a zero-point and
mne the "start" trigger that occur earlier (i.e. you can follow the signal
but it will be not saved in the file), but I'm not perfectly sure.

As someone already observed this difference?
It's harmless because it doesn't affect relative timing of the event but
become problematic to transfer recoded events trl from fieldtrip to
mne-python with a time-sample matching strategy.



Baptiste Gauthier
Postdoctoral Research Fellow

INSERM-CEA Cognitive Neuroimaging unit
CEA/SAC/DSV/DRM/Neurospin center
Bât 145, Point Courier 156
F-91191 Gif-sur-Yvette Cedex FRANCE
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