[FieldTrip] Filter settings (Fieldtrip vs Brainvision Analyzer)

[Mark Noordenbos]

Dear all,

I analyzed some data using Brainvision Analyzer and would like to re-analyze
the same data using Fieldtrip. However, the final results are a bit
different between Brainvision Analyzer and Fieldtrip.
The main difference is because of differences in filtering of the data
(without filtering the data is exactly the same). The filter in Fieldtrip
seems to be much 'stricter' and as a consequence the amplitude is almost
halved in the grandaverage!

In Brainvision Analyzer I used the following filter setting:

Butterworth Zero Phase Filters
Low Cutoff: 1.0000 Hz, Time constant 0.1592s, 24 dB/oct
High Cutoff: 30.0000 Hz, 24 dB/oct
Notch Filter: ---

In Fieldtrip I used the following filter settings

cfg.lpfilter                = 'yes';
cfg.hpfilter                = 'yes';
cfg.lpfreq                  = 30;
cfg.hpfreq                  = 1;

cfg.lpfiltord = 6;
cfg.hpfiltord = 6;

cfg.lpfiltdir     = 'twopass';
cfg.hpfiltdir     = 'twopass';

Any suggestions for the Fieldtrip filter settings to resemble the
Brainvision Analyzer filter settings as much as possible?

Best,
Mark
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