minor problem loading fiff file

[Jan Hirschmann]

Hi,

this is my very first day with fieldtrip so there is some chance that the error is due to the user rather than to the code... Anyways, I had the following problem. I loaded a fif file using preprocessing which did not start a time 0 but later. I got an a error from the mne function fiff_read_raw_segment saying that there is no data in this range. I tried to define the trial differently setting trl in different ways but it didn't help so I looked at the code. Preprocessing calls the function read_header which said that nSamplesPre were -6031500 in my case. So I guess this means that there are samples missing between a trigger (I don"t know which) and the start of the file. Later in preprocessing the function read_data calls fiff_read_raw_segment with the following arguments:
read_data.m, line 691.m: dat = fiff_read_raw_segment(hdr.orig.raw,begsample+hdr.nSamplesPre-1,endsample+hdr.nSamplesPre-1,chanindx);
Thus fiff_read_raw_segment is launched with negative to and from values which finally causes the error. nSamples should have been subtracted here and not added (it is a negative integer).
I would suggest that in the future the call to the function should be only with arguments coming from the header file, i.e. from = hdr.orig.raw.last_samp and to = hdr.orig.raw.first_samp or that the pluses in the quoted line should be changed to minuses (which I did now in my version). However, I don't know if my file is strange (neg nSamplesPre) or if the code has a bug.

Hope this helps anyone

Best,

Jan


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