node-lsl

Lab Streaming Layer (LSL) for synchronized streaming of multi-modal, time-series data over a network.

Table of Contents

• Overview
• Installation
• Usage
  • LslStreamOutlet
  • LslEventMarkerEmitter
• Test Doubles

Overview

This package is a Node wrapper around the C++ liblsl library. It was developed and tested on a MacOS system with an M2 chip. It should work with any M-series chip: M1, M2, M3. There are known issues for this package with x86 MacOS architectures. It's untested for Windows or Linux.

Please note that this package currently only supports LSL outlets (sending data over a network). It does not yet support LSL inlets (receiving data from a network).

Installation

First, you need to install the C++ liblsl library. On MacOS, you can use Homebrew to install it, as specified in its documentation:

brew install labstreaminglayer/tap/lsl

Then, install the package with your preferred package manager (make sure to be in the right directory for your Node project):

npm install @neurodevs/node-lsl

or

yarn add @neurodevs/node-lsl

Finally, add the following to your .env file or otherwise set it as an environmental variable. Update the path to match your system:

LIBLSL_PATH=/opt/homebrew/Cellar/lsl/1.16.2/lib/liblsl.1.16.2.dylib

Usage

LslStreamOutlet

LSL is often used to stream EEG data over a network. For example, to instantiate an LSL outlet for the Muse S 2nd generation headband:

import { LslStreamOutlet } from '@neurodevs/node-lsl'

const outlet = await LslStreamOutlet.Create({
    name: 'Muse S (2nd gen)',
    type: 'EEG',
    sourceId: 'muse-s-eeg',
    channelNames: ['TP9', 'AF7', 'AF8', 'TP10', 'AUX'],
    channelFormat: 'float32',
    sampleRateHz: 256,
    chunkSize: 12,
})

outlet.pushSample([1, 2, 3, 4, 5])

LslEventMarkerEmitter

LSL is also often used to push event markers that mark different phases of an experiment or session. The emitMany method pushes an event marker, waits for a specified duration, then pushes the next marker. From experience, each event marker should have a waitForMs of at least 100 ms or so to ensure LSL receives the event markers in the right order.

import { LslEventMarkerEmitter } from '@neurodevs/node-lsl'

const emitter = await LslEventMarkerEmitter.Create()

const markers = [
    { name: 'phase-1-begin', waitForMs: 1000 },
    { name: 'phase-1-end', waitForMs: 100 },
]

const promise = emitter.emitMany(markers)

emitter.interrupt()