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BioSemi Import ​

This demo demonstrates importing BioSemi BDF files into EegFun.jl.

What is BioSemi BDF Format? ​

BioSemi is a popular manufacturer of active electrode EEG systems. The BDF (BioSemi Data Format) is a 24-bit variant of the European Data Format (EDF) designed specifically for BioSemi's ActiveTwo and ActiveOne systems.

Key features:

  • 24-bit resolution for high-precision recordings

  • Continuous raw data storage

  • Trigger channel for event markers (last channel)

  • Standard format widely supported across analysis tools

Import Capabilities ​

Data loading:

  • Raw continuous EEG time series (24-bit precision)

  • Sampling rate and channel metadata

  • Trigger/event markers (encoded in Status channel)

What you need:

  • .bdf file (contains all data)

  • Electrode layout file matching your cap configuration

  • BioSemi systems typically use standard cap layouts (16, 32, 64, 72, or 128 channels)

Data Mapping ​

EegFun.read_raw_data loads BioSemi data, then create_eegfun_data converts to native EegFun types:

  • BioSemi BDF → BiosemiData (intermediate) → ContinuousData (EegFun)

  • Triggers extracted from Status channel

  • Layout coordinates added separately

Important Notes ​

Layout Files ​

BioSemi doesn't embed electrode positions in the data file, so you must provide a matching layout. EegFun includes standard BioSemi layouts in resources/layouts/biosemi/:

  • biosemi16.csv

  • biosemi32.csv

  • biosemi64.csv

  • biosemi72.csv (64 + 8 external channels)

  • biosemi128.csv

Choose the layout matching your recording setup.

Trigger Encoding ​

BioSemi encodes triggers in a dedicated Status channel using binary encoding. EegFun automatically extracts these during import, making them available via trigger_count() and epoch extraction functions.

Workflow Summary ​

This demo shows the complete BioSemi import workflow:

Load Raw BDF Data ​

  • Use read_raw_data() with path to .bdf file

  • Automatic format detection based on file extension

Prepare Layout ​

  • Load appropriate BioSemi layout file

  • Convert polar coordinates to cartesian for visualization

Create EegFun Data Structure ​

  • Combine raw data with layout using create_eegfun_data()

  • Results in ContinuousData ready for analysis

Code Examples ​

Show Code
julia
# Demo: Loading and Processing BioSemi BDF Files
# Shows how to load BioSemi .bdf files, create EegFun data structures
# with layouts, and get the triggers/events.

using EegFun
# Note: EegFun.example_path() resolves bundled example data paths.
# When using your own data, simply pass the file path directly, e.g.:
# dat = EegFun.read_raw_data("/path/to/your/data.bdf")

# Load raw BDF data
# read_raw_data automatically detects the .bdf extension
raw_data = EegFun.read_raw_data(EegFun.example_path("data/bdf/example1.bdf"))

# EegFun uses the Julia package: BiosemiDataFormat.jl
# https://github.com/igmmgi/BiosemiDataFormat.jl

raw_data.header.channel_labels  # electrode labels
raw_data.header.sample_rate     # sampling rate
raw_data.header.num_channels    # number of channels
raw_data.data
raw_data.triggers

# Load and prepare electrode layout
# BioSemi systems typically use their standard cap configurations
layout = EegFun.read_layout(EegFun.example_path("layouts/biosemi/biosemi72.csv"))
EegFun.polar_to_cartesian_xy!(layout)

layout.data # DataFrame with labels and positions

# Create EegFun data structure
dat = EegFun.create_eegfun_data(raw_data, layout)

EegFun.all_data(dat)
EegFun.meta_data(dat)
EegFun.all_labels(dat)
EegFun.channel_labels(dat)
EegFun.meta_labels(dat)
EegFun.extra_labels(dat) # empty

# Check trigger information
EegFun.trigger_count(dat) # BioSemi data uses 8 bit trigger lines

See Also ​