[Eeglablist] Reading large bdf file

[Jingjiang Lei]

Hi Arno, Ha, Ryan, Jeff and all,

I like EEGLab and its open-source style. I also met the large bdf file
problem our file is about 1G. Before MatLab next version I want to do
something and I think the speed of file size increace maybe faster then
the speed of MatLab version updata. I think for the large data file we
can not read all channels and all recorod time i.e. all data in one
data file into memory in a time. 

Ryan (who post on the maillist on March) and others mentioned "import
BDF file data one channel at a time" is one way to deal with large size
problem. Another way is read all channel but only for a small time
prieod(epoch). 

I just wrote a plugin to read BDF file data one channel at a time into
EEGLab and store the data EEGLab's data structure. After that you can
use all EEGLab's function to play around it for example, you can use
Plot>>Channel data(scroll) to show the data; if the channel you read is
event channel you also can use File>>Import evet info>>From data
channel to get event information(when you do this please unselect
"Delete event channel" check box). 

I am very happy to share this with all of you. This plugin include
three M files which is attched with this emial. If you want to try it,
please 1)put the eegplugin_readBDFchan.m to the plugins folder; 2)make
a BDFchan folder inside plugins folder; 3)put the pop_readBDFchan.m and
readBDF_chan.m to the BDFchan folder. Next time when you start EEGLab,
EEGLab will automatically include this plugin. You will see a new item
"read BDF specify channel" in the bottom of File>>Import Data menu.

Thanks,

Jingjiang Lei, Ph. D.

Psychology Dept. 

McMaster University


On Wed, 19 May 2004 15:40:37 -0700
 Arnaud Delorme <arno at salk.edu> wrote:
> We are using BDF files too and have memory problems too. You may read
> a portion of your file, resample, then read another portion of your
> file, resample, then concatenate the two portions (you should select
> portions of file with an overllap, then suppress the beginning and
> end of your data for each portion of file to minimize resampling
> artifacts).
> 
> The next version of Matlab will allow processing of 32-bit float
> numbers and will solve a lot of memory problems for EEG analysis.
> 
> Arno
> 
> > I’m reading .bdf file and facing the problem of not being able to
> read 
> > large file.
> >
> > My bdf file is 711 secs long, eeglab used about 500MB of ram (I
> have 
> > 1.5GB RAM) and gave me ‘out of memory’ error.
> >
> > Do anyone know is this a limitation on matlab or is there any way I
> 
> > can read such a big file
> >
> 
> -- 
> 
> *Arnaud Delorme, Ph.D.*
> Computational Neurobiology Lab, Salk Institute
> 10010 North Torrey Pines Road
> La Jolla, CA 92037 USA
> 
> *Tel* : /(+1)-858-458-1927 ext 15/
> *Fax* : /(+1)-858-458-1847/
> *Web page *: www.sccn.ucsd.edu/~arno
> <http://www.sccn.ucsd.edu/%7Earno>
> *To think upon*:
> 
>     I much prefer the sharpest criticism of a single intelligent man
> to
>     the thoughtless approval of the masses.
> 
>         /Johann Kepler/  
> 
> 
> 
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