[FieldTrip] problem with reading .edf+ files
r.oostenveld at donders.ru.nl
Thu Dec 6 22:44:54 CET 2012
The EDF and derived formats (EDF+, BDF, GDF) write the data as short segments in the file. Usually the subsequent segments can be glued together to form a continuous representation, but that is not guaranteed by the fileformat.
I cannot check at the moment, as I don' have an EDF file handy, but I would expect that if you specify cfg.continuous='yes' to ft_preprocessing that it will be interpreted as a single continuous recording, rather than as an epoched recording.
On 5 Dec 2012, at 17:07, Schönherr, Margit wrote:
> I want to analyze invasive EEG data and I have problems reading the data correctly. The data are continuous and I used BESA to convert them to .edf format. When I read them into matlab, however, the data are not continuous anymore, but segmented into very short trials. For example, a data set of 1 hour is split into 8229 trials of 0.43 s length. Even more confusing, the trial length differs across subjects.
> What is the difference between .edf and .edf+? BESA Research produces the latter, could this be the reason for the issue?
> I also tried to track down the place where the segmentation into trials is done, but I ended up at line 111 of read_edf.m (EDF.Dur = str2num(H1(245:252)) % 8 Byte # duration of data record in sec).
> I would be very glad if someone could tell me, how to read the data correctly with fieldtrip. Thanks!
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