[FieldTrip] read_biosig_header.m

Steve Deiss sdeiss at ucsd.edu
Tue Jul 10 20:49:49 CEST 2012

The fieldtrip version we have calls function 'read_biosig_header' which 
calls 'sopen' with the following sequence.
      biosig = sopen(filename,'r');
For some reason it loses the digital triggers on channel 1 in our data 
after issuing the following warning:

"Reading data file header...
WARNING SOPEN(EDF): Physical Max/Min values of EDF data are not 
necessarily defining the dynamic range.
    Hence, OVERFLOWDETECTION might not work correctly. See also EEG2HIST 
and read
    http://dx.doi.org/10.1016/S1388-2457(99)00172-8 (A. Schlgl et al. 
Quality Control ... Clin. Neurophysiol. 1999, Dec; 110(12): 2165 - 2170).
    A copy is available here, too: 
http://www.dpmi.tugraz.at/schloegl/publications/neurophys1999_2165.pdf "

If we let EEGLAB read the data, its function 'pop_biosig' calls 'sopen' 
      biosig = sopen(filename,'r',0,'OVERFLOWDETECTION:OFF');
The data read in here includes the triggers so that we can go on to 
epoch and process the data.

We are not yet ready to upgrade to the very latest fieldtrip.  So I 
would like to know if there is an easy way to
determine if the latest version of fieldtrip changed anything in the way 
sopen is called from read_biosig_header?
If it matches what EEGLAB does here, we can match that as a temporary fix.

I'll try to download and unpack it to see, but if this is a known 
problem, fixed or not, I'd appreciate any tips.


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