preprocessing slowing down

[Bernhard Staresina]

Dear FieldTrip users,

A quick question on preprocessing. I noticed that as I preprocess my EEG
data (no actual preprocessing settings, just getting the exportet raw data
into FieldTrip format), the process dramatically slows down as it goes
along. So by trial 100, MATLAB essentially stops. I don't think it's a
working memory issue - I tried to preprocess only the last few trials with
cleared working memory, and the process doesn't move on. 
I read in the trial information (beginsample, endsample and offset) via
definetrial, and of my ~700 trials (with only 25 channels), the later trials
have begin- and endsample values of eg. 4338002 and 4344000, respectively.
But why is it that it takes longer to read in a trial as a function of its
begin and end sample? Shouldn't the amount of preceding data points be
irrelevant?
I'm reading in BrainVision Analyser data, using FT version
'fieldtrip-20090120'. The segments are 5.9 sec long, with 1kHz sampling rate. 

Thanks,
Bernhard

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