LSL streaming issue

prag

Hi, I used openbci-gui to LSL stream my 8 channel data with help of link: https://docs.openbci.com/docs/06Software/01-OpenBCISoftware/GUIWidgets#lsl
and am listening to the stream via lab recorder.
When I look at the streamed / recorded data later, I see a weird pattern, there is no consistent 250Hz sampling of data. After every 10 samples there is a jump, for example data.time_stamps(2) - data.time_stamps(1) is 0.004, and data.time_stamps(11) - data.time_stamps(10) = ~30, and this pattern is quite consistent for every 10 values in sequence. I’m not sure what is happening, and how I should rectify this problem. Please help.
@wjcroft @retiutut @evaesteban

retiutut

How are others supposed to view .xdf data to see what is happening? I tried opening in TextEdit and it is not human-readable.

prag

I generally read it in Matlab using load_xdf function (ex: https://github.com/xdf-modules/xdf-Matlab).

retiutut

Going to try this http://www.openxdf.org/editor.php on my Windows machine.

prag

Thank you for helping me, looking forward to solve the problem.

retiutut

I have just run a test using Synthetic data over LSL to Lab Recorder with filter On. Then, use https://github.com/cbrnr/sigviewer to look at Channel 1 (5Hz Sine Wave). The data does not look like a sine wave . I think this aligns with the actual vs expected sample rate using the existing Networking test scripts. I will take a look at this.

retiutut

I've just gone through the complete data pipeline for LSL TimeSeries output, and it looks fine for Cyton 8Ch @ 250Hz. Tested using Cyton, GUI 5.0.1, and BrainVision LSL Viewer while generating square waves on the Cyton.

prag

Thank you very much! I was using GUI4.2.0 earlier and upgrading to GUI5.0.1 per your suggestion solved the problem.

retiutut

GUI v5.0.2 will have a fix included for LSL Output when Filter toggle is on.

prag

I don't see GUI5.0.2 in the website https://openbci.com/index.php/downloads. How can I access it?

retiutut

It's still being worked on!

prag

Thanks, Could you kindly list the differences I can expect between GUI5.0.1 vs. GUI5.0.2 with respect to LSL output?

retiutut

Thanks, Could you kindly list the differences I can expect between GUI5.0.1 vs. GUI5.0.2 with respect to LSL output?

During my tests comparing LSL visualizer to GUI with TimeSeries output, the data was unrecognizable. With the change below, it should look like actual data with whatever filter settings are set in the GUI.

Here is the closed Github issue: https://github.com/OpenBCI/OpenBCI_GUI/issues/880#issuecomment-696131797

Here is the one-line fix: https://github.com/OpenBCI/OpenBCI_GUI/pull/879/commits/b2dbfbce2b697e0b4110776c52ec751834993f47