[FieldTrip] zero-padding at beginning of file does not work

[Frederic Roux]

Dear all,

I want to pad out my signal before applying some filters while
reading the data from the original ds-file.

at line 578 of the preprocessing.m function it says:

begsample = cfg.trl(i,1) - begpadding;

Now because my signal starts at sample 1, begsample will have a negative value of course
which results in the warning message

warning('cannot apply enough paddig at begin of file');

Does that mean, that fieldtrip cannot pad out the signal at the beginning without
throwing away the equivalent of the signal in itself?

if cfg.trl(i,1) = 2400 and if begpadding = 1200 this should work, because begsample = 1200, right?
But that would also mean that for padding I would loose 1200 samples.

Now let's assume I would like to pad the signal to -25 sec and + 25 sec at the beginning and end.
Why does the padding at the beginning require I throw away 25 sec, while the padding at the end doesn't?

Any clarification on this issue would be greatly appreciated.

Have a nice day.

Fred

-- 
Frédéric Roux, PhD student
Department of Neurophysiology
Max Planck Institute for Brain Research
D-60529 Frankfurt am Main
Frederic.Roux at brain.mpg.de
+49(0)69630183225


 		 	   		  
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