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<div class="moz-cite-prefix">Hi Dwight and all,<br>
<br>
I've seen this memory issue for awhile now and it seems that is
going to be very common in the era of multi-modal eeg analysis.
Re-sampling high density EEG up to audio sampling rates does not
seems to be the plausible solution because it will result in a
ridiculous large datasets. One solution would be using EEGLAB's
memory mapping mechanism (EEGLAB's menu -> File-> Options),
although is not clear how to represent the audio signal if both,
EEG and multi-channel audio are very large, matlab matrices?,
additional channels in EEG.data?, buffering chunks from files?,
etc. I've addressed this issue in a toolbox called MoBILAB (MoBI
stands for Mobile Brain/Body Imaging), I'm not sure if is shipped
with EEGLAB at this moment. Anyway, the toolbox represents each
different stream of data as an object, each object can have
different sampling rate, and properties, underneath the data is
stored in a file that is being memory-mapped, so when you do
">> object.data" you're accessing the data in matrix,
meanwhile the OS is taking care of fetching from disk the chunks
you actually need. MoBILAB can export data back and forth from/to
EEGLAB if the EEG structure is no very convoluted. Check the
website below if you're interested.<br>
<br>
Ok, done with my little bit of advertisement, the main point I
want to make is this, if your have collected different modalities
in some synchronous way (see LSL website for a reference of how to
do that), and all the streams were properly sampled, then you
probably don't have to resample them to make them match sample by
sample, instead of "walking" in sample points you would walk in
time, is what I do in my MultiStream Browser (visualization tool
for multi-modal data). I'd advise only resampling those channels
(chunks) you going to work with in internal functions and return
the results back in the original sampling rate of the input data.
Observe that keeping EEG datasets at 40 kHz will fill up your disk
pretty quickly. Also, check out Matlab timeseries's resample
method for a simple way of resampling two time series to a common
time base.<br>
<br>
Regards,<br>
Alejandro<br>
<br>
relevant links:<br>
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<a href="http://code.google.com/p/mobilab/">http://code.google.com/p/mobilab/</a><br>
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charset=ISO-8859-1">
<a
href="http://sccn.ucsd.edu/wiki/Mobilab_software#Shortcut_to_practical_chapters">http://sccn.ucsd.edu/wiki/Mobilab_software#Shortcut_to_practical_chapters</a><br>
<br>
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charset=ISO-8859-1">
<a href="http://code.google.com/p/labstreaminglayer/">http://code.google.com/p/labstreaminglayer/</a><br>
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charset=ISO-8859-1">
<a
href="http://www.mathworks.com/help/matlab/ref/timeseries.resample.html">http://www.mathworks.com/help/matlab/ref/timeseries.resample.html</a><br>
<br>
<br>
<br>
On 09/21/2012 02:32 PM, Dwight Peterson wrote:<br>
</div>
<blockquote
cite="mid:CACA--BJUh8cOqs91NSOXw2nSbA4Dd3tF=7b+-nvBx9ePPrAi6w@mail.gmail.com"
type="cite">Hi all,
<div><br>
</div>
<div> I am getting an output message of OUT OF MEMORY quite
often when attempting to use certain functions within EEGLAB.
For example, this OUT OF MEMORY message occurs when I try to
re-sample my dataset after it has been successfully loaded in to
EEGLAB. The reason I am trying to re-sample is because our data
acquisition system is extremely high resolution, however, this
leads to memory issues given that the sampling rate is 48000 Hz.
Because we are limited in terms of our equipment, I was trying
to re-sample to a smaller sampling rate, but I keep getting this
error message. Also, this error message comes up when I try to
load in a saved continuous EEG dataset that I have already
processed. However, if I re-create the eeg dataset from the
beginning (e.g., import > from .mat array) there is no such
error message. </div>
<div> I have already tried the memory options within the
File menu of the EEGLAB GUI. </div>
<div><br>
</div>
<div> Any suggestions would be most appreciated!</div>
<div><br>
</div>
<div>Thanks!</div>
<div><br>
</div>
<div>--Dwight--</div>
<div>
<div><br>
</div>
-- <br>
Dwight J. Peterson, M.A.<br>
Graduate Assistant<br>
Cognitive and Brain Sciences<br>
Department of Psychology/296
<div>Memory and Brain Laboratory<br>
University of Nevada, Reno<br>
Reno, NV 89557<br>
Cellular: 319-231-8596</div>
<div>Laboratory: 775-682-8667</div>
<br>
</div>
<br>
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