Lab Streaming Layer (lsl): Which variable in the Matlab workspace is the raw streamed data?

KCDTyler · May 2019

Hi all,

I have managed to stream EEG into Matlab using lab streaming layer and BCILAB. But it is not clear to me how exactly to access the raw streamed data, in order to run analysis on it etc.

Can anyone help with this?

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I open the stream from the Mac terminal using lab streaming layer.

I open BCILAB within Matlab.

I send the streamed data to Matlab, either using the BCILAB GUI, or with a command such as: run_readlsl('DataStreamQuery','type=''EEG''', 'MarkerQuery','');

The Matlab workspace then shows a range of variables, such as the structure 'laststream' and the variable 'laststream_chunk_clr' which is (8X13) double, and updates over time, as the streamed data comes in.

If I want to write some simple analysis code, such as some form of spectral analysis to calculate the power of alpha over time, which data variable in the Matlab workspace do I actually use?

It can't be the 'last stream_chunk_clr because that is only 13 columns/time points.

Can anyone help with this?

*******

I have looked through the OpenBCI forum, and had a look at many of the LSL tutorial youtube clips, but I can't see anything that explains this very basic issue.

Thanks in advance!

Kaelasha

Billh · May 2019

I have not used BCILAB, but its docs suggest it is "lazy" in its default configuration and may not actually load the data beyond the header until told to do so:

https://sccn.ucsd.edu/wiki/BCILAB#Loading_data

wjcroft · May 2019

Kaelasha, hi.

I would suggest postponing the BCILAB usage because that adds another layer of complexity on top of Matlab and EEGLAB. If you just want to access the data stream from within your Matlab program, have you looked at the LSL tutorial examples?

https://github.com/sccn/labstreaminglayer/wiki/ExampleCode

https://github.com/labstreaminglayer/liblsl-Matlab

Perhaps after you get your stream reading working, THEN experiment with integration of EEGLAB / BCILAB.

Regards,

William

Lab Streaming Layer (lsl): Which variable in the Matlab workspace is the raw streamed data?

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