[FieldTrip] Working with xdf files

[Schoffelen, J.M. (Jan Mathijs)]

Dear Varghese,

In general, I think that workarounds should be avoided as much as possible, unless one wants to achieve something very exotic.

In your case, it seems that the required functionality is something that more people might benefit from, in which case a generic/principled solution would be in order.

This would mean that xdf2fieldtrip should be made smarter so that it also returns the events. The ’streams’ are read in using the lower level load_xdf function (located in external/xdf), but at the moment only the continuous data is returned. What you need to do is to write some code that can extract event information from the discontinuous stream (ideally in a fieldtrip compatible event-structure), and pass this as an output to the function.
Once the code is up and running, we’d be happy to receive a pull request on github, so that other users can benefit from this functionality!

Thanks and happy computing.

Jan-Mathijs




On 27 Aug 2019, at 08:54, Varghese Peter <V.Peter at westernsydney.edu.au<mailto:V.Peter at westernsydney.edu.au>> wrote:

Dear fieldtrip community,

I am working with EEG files in the xdf format recorded using the Lab Recorder program. I used the ‘xdf2fieldtrip function to import the data in the fieldtrip format. I got the output as follows:

stream 1 contains continuous LiveAmpSN-054208-0189 data
stream 2 contains non-continuous Presentation data

data =

  struct with fields:

      hdr: [1×1 struct]
    label: {32×1 cell}
     time: {[1×545430 double]}
    trial: {[32×545430 single]}

I want to use the Presentation stream (events) to epoch the data. Since ‘ft_definetrial’ require data in the original format and the xdf format is not supported in the ‘ft_preprocessing’, is there a workaround?

Thanks,
Varghese Peter

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