[Eeglablist] Large data file appears empty

[Michael Boyle]

I have had some experience loading files that looked like there was no data
in the sense that everything was railed for the entire recording. We got
around this by applying a 0.1Hz high-pass filter in the software tools
provided by the company that built our acquisition system (EGI in our case)
before loading it in EEGLAB. This immediately solved the issue, but I can't
really say why (I'm not sure if the data in the EGI native file format are
double-precision floats or not so I can't chalk it up to a precision issue
converting double to float when large DC offsets are present). Might this
be the case here?

Michael

On Wed, Aug 26, 2015 at 1:11 PM Andreas Widmann <widmann at uni-leipzig.de>
wrote:

> Any error messages? How do you diagnose that „there’s no data“? Please,
> preferably file a bug report to EEGLAB bugzilla including a sample data set
> (eeg + vhdr + vmrk) and code demonstrating the problem or upload the data
> to some file hoster and post the link to the forum.
>
> Best,
> Andreas
>
> > Am 25.08.2015 um 17:41 schrieb Lexie Tabachnick <ltabachnick at gmail.com>:
> >
> > We have been running an experiment trying to collect ABR data using the
> Brainvision EP-PreAmp and Actichamp system. We ran several successful tests
> with short versions of our experiment, about 10-15 minutes of recording. We
> were able to process the data in eeglab and saw the components we were
> expecting.
> >
> > We have recently been running our full experiment, recording for about
> 45-50 minutes. The files are necessarily much bigger. The test .eeg files
> were ~150mb and the full .eeg files are ~550mb. All of our Brainvision
> equipment seems to working (amps, batteries, electrodes), and we are able
> to get our impedances low before recording. However, when we import the
> vhdr files into eeglab, it looks like there's no data there. We are
> thinking this might be an eeglab problem - perhaps the file is too large
> and something's getting lost in the import?  Any advice would be greatly
> appreciated.
> >
> > Thanks!
> > Lexie
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