[Eeglablist] Out of memory

[Andrew Hill]

Hi Ben,

Only when running a 64-bit version of your hardware/operating system and 64-bit Matlab can you address enough RAM to import huge files - that might be a factor if you are experiencing different behavior on different machines.   I can only get Windows/Mac 32-bit machines to import about 350-400mb files max, either .bdf or .cnt.

Out of memory is a common problem when importing from other formats, b/c if i recall correctly Matlab makes more than one copy of the data on import.  Not sure if it's true with the bdf import you are using (there are a couple in EEGLab, and I don't know what either is doing)

Various workarounds exist, like first selecting a subset of channels, segmenting the recording (and then importing and appending .sets), and discarding the DC information to convert your .bdf to .edf - this is assuming your bdf is BioSemi.   If so, grab the Converter utility here http://www.biosemi.com/download.htm and "convert" your file.  this will discard the offset (default settings should be fine) and the resulting file will be a lot smaller and easier to import.  

You may want to detrend your data afterwards to ensure the the offset is cleanly out (using something like EEG.data = detrend(EEG.data); )  I've not seen it make much difference in my data, but have also seen it recommended with importing BioSemi data. 

There are also Reducer and Cropper tools available at that same link for channel/time selection, and a Decimator tool that can reduce the sampling rate if you recorded at some larger than necessary

Best,
Andrew


On Nov 9, 2010, at 6:18 AM, Benjamin Kuhr wrote:

> Hi,
> 
> I tried to import a large *.bdf file, 614 MB. I get the "Out of memory" -
> message, but not on all computers and for some reason it seems as it does
> not depend on the actual memory. It works on a weaker system, but not on
> the current one, which has 3.8 GiB of memory and a Intel Core 2 Duo CPU
> R7500 @ 2.93 GHz.
> 
> Even on identical systems with the same hardware and same software I can
> load the file only on one of them. I tired it with Windows XP and Ubuntu
> 10 on the system mentioned above, no difference. Any suggestions?
> 
> Thanks in advance
> Benjamin Kuhr
> 
> 
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