LSL Bindings

Low-level Dart bindings to the Lab Streaming Layer (LSL) C API.

This package provides direct access to the native LSL interface via Dart FFI and is intended for advanced users who require fine-grained control over streaming or receiving LSL data in Dart or Flutter applications.

If you're looking for a higher-level, idiomatic Flutter API for working with LSL, consider using lsl_flutter, which builds on top of this package.

Features

  • Direct Dart FFI bindings to the LSL C API
  • Cross-platform support: macOS, iOS (via .xcframework), Windows, and Android

Getting started

  1. Add dart:ffi as a dependency, as it is needed for memory management and type conversion.

  2. Add the plugin to your pubspec.yaml (or flutter pub add lsl_bindings):

dev_dependencies:
  ffi: ^2.1.3
dependencies:
  lsl_bindings: ^0.0.5

Usage

import 'package:lsl_bindings/lsl_bindings.dart';

/// Create a stream info object
final streamInfo = lslBindings.lsl_create_streaminfo(
  "Test stream".toNativeUtf8().cast<Char>(),
  "EEG".toNativeUtf8().cast<Char>(),
  4,
  256,
  lsl_channel_format_t.cft_double64,
  "Source id".toNativeUtf8().cast<Char>());

Android

The minimum SDK version must be set to 26 in app/build.gradle. This is due to the logging library used by LSL, Loguru.

// app/build.gradle
minSdk = 26

The AndroidManifest.xml must contain

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.CHANGE_WIFI_MULTICAST_STATE" />

Also note, that in conjunction with the multicast permission specified above, a multicast lock must be acquired to make streams from Android devices discoverable. This is due to the fact that Android devices, by default, do not accept multicast packet traffic. carp_multicast_lock is for example used in the more opinionated lsl_flutter package.

iOS

Minimum deployment target must be set to at least 14 in ios/Podfile

platform :ios, '14.0'

The Info.plist for applications using the plugin must specify a reason for accessing the local network

<key>NSLocalNetworkUsageDescription</key>
<string>This app needs local network access to discover data streams.</string>

Furthermore, the entitlement com.apple.developer.networking.multicast must be applied for from Apple with a justification in order to discover streams on iOS devices. This can take several working days.

Runner.entitlements must therefore include the following

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
  <dict>
    <!--...-->
    <key>com.apple.developer.networking.multicast</key>
    <true />
    <!--...-->
  </dict>
</plist>

macOS

The same entitlement as in iOS must be granted or the app can be de-sandboxed as illustrated in the image below.

image

Libraries

lsl_bindings
A library for interacting with the Lab Streaming Layer