User Reference:Validating the Event Logging Mechanism

Synopsis

BCI2000 is able to record asynchronous data, so called Events, that occur during a recording. These events are logged into BCI2000 states, which provide a universal way to store information associated with brain signal sample data.

This page provides an overview over the general concept and implementation of events.

Also, it describes the RefLogger, which allows to quantify how reliable event recording is, and shows a simple Matlab script to analyze RefLogger data, together with results from a reference system.

The Event Logging Mechanism

As described elsewhere, BCI2000 processes brain signal data in blocks of fixed size and duration. Whenever a block of data has been acquired from the main brain signal source, a time stamp is taken from the computer's clock. Note that this time stamp is taken after the data block has been sampled and transmitted from the hardware. Assuming a negligible time delay between sampling of the block's last sample, and transmission into the computer, we can say that this time stamp represents the time of sampling for the first sample of the following block. Knowing this time stamp, and the sampling rate of the brain signal source, we can thus associate each of the block's samples with a sample time.