error with LSL

[lucasbenoit]

Hi
I would like to use the mne library to read eeg signal in real time with LSL and the OpenBCI gui.
When I run the script plot_lslclient_rt.py , the terminal tells me that the LSL connection works but closes directly after , the error comes from the function client.start_receive_thread(8) .
Here is my error in the terminal :

"Opening raw data file C:\Users\sc01484\mne_data\MNE-sample-data/MEG/sample/sample_audvis_filt-0-40_raw.fif...
Read a total of 4 projection items:
PCA-v1 (1 x 102) idle
PCA-v2 (1 x 102) idle
PCA-v3 (1 x 102) idle
Average EEG reference (1 x 60) idle
Range : 6450 ... 48149 = 42.956 ... 320.665 secs
Ready.
Reading 0 ... 4505 = 0.000 ... 30.003 secs...
Removing projector <Projection | PCA-v1, active : False, n_channels : 102>
Removing projector <Projection | PCA-v2, active : False, n_channels : 102>
Removing projector <Projection | PCA-v3, active : False, n_channels : 102>
Client: Waiting for server to start
Looking for LSL stream openbcigui...
Found stream 'obci_eeg1' via openbcigui...
Client: Connected
Got epoch 1/100
Exception in thread Thread-9:
Traceback (most recent call last):
File "C:\Users\sc01484\Anaconda3\lib\threading.py", line 932, in _bootstrap_inner
self.run()
File "C:\Users\sc01484\Anaconda3\lib\threading.py", line 870, in run
self._target(*self._args, **self._kwargs)
File "C:\Users\sc01484\Anaconda3\lib\site-packages\mne_realtime\base_client.py", line 16, in _buffer_recv_worker
for raw_buffer in client.iter_raw_buffers():
File "C:\Users\sc01484\Anaconda3\lib\site-packages\mne_realtime\lsl_client.py", line 83, in iter_raw_buffers
yield np.vstack(samples).T
File "<array_function internals>", line 5, in vstack
File "C:\Users\sc01484\Anaconda3\lib\site-packages\numpy\core\shape_base.py", line 283, in vstack
return _nx.concatenate(arrs, 0)
File "<array_function internals>", line 5, in concatenate
ValueError: need at least one array to concatenate
Streams closed"

Does anyone have a solution to this error?

[teonbrooks]

Hi there @lb162215. For the plt_lslclient_rt.py example, it is using the MockLSLClient for the example. I can help point out what you might need to modify it to work with your hardware. How are you currently creating the LSL stream for your openbci?

[lucasbenoit]

@teonbrooks I deleted the part concerning the MockLSLclient, I changed the host variable to "openbcigui".
Concerning Openbci I do it from the Gui ( v5.0.3) with the networking - LSL function , with a TimeSeries send.

[timonmerk]

Hey @lb162215, the hostname would be in this case the "Stream ID" and not the Name.

I could use the command line with python openbci_lsl.py --stream to create a stream that I could then read using this code:

import mne
from mne.io import read_raw_fif
from mne_realtime import LSLClient

# this is the max wait time in seconds until client connection
wait_max = 5

info = mne.create_info(ch_names = ['Fp1', 'Fp2', 'C3', 'C4', 'T5', 'T6', 'O1', 'O2'], \
                      sfreq=250, ch_types="eeg")

with LSLClient(host="openbci_eeg_id203", info=info, wait_max=wait_max) as client:
    client_info = client.get_measurement_info()
    sfreq = int(client_info['sfreq'])
    print(client_info)
    
    epoch = client.get_data_as_epoch(n_samples=sfreq)

So here you replace the host, channel names and frequency as displayed by openbci_lsl:

I am happy to help furtheron if this should not work :)

[lucasbenoit]

@timonmerk Hello, unfortunately I can't use this technique to find out the host name. I don't have the hardware at the moment, I use the playback function of the GUI and I launch the LSL of this one.

[teonbrooks]

@lb162215 is there an option in the OpenBCI GUI to specify the device id for playback mode?

[timonmerk]

Looks like the Stream ID can be changed (from https://docs.openbci.com/docs/06Software/02-CompatibleThirdPartySoftware/LSL and https://github.com/openbci-archive/OpenBCI_LSL/blob/master/lib/gui.py)

[lucasbenoit]

@teonbrooks @timonmerk
Yes there is one . I use this id since the beginning , that's called 'obci_eeg1' in my error message . I tried with others ID and it's still doesn't work .