BCI2000 Glossary

Sample Block

BCI2000 processes data in chunks, which are called Sample Blocks, or Data Blocks. State variables are saved with each sample, but may only change once per sample block. Sample block size is configured through the SampleBlockSize parameter; often, ADC hardware imposes restrictions on sample block size.

The physical duration of a sample block is the inverse of the screen update rate, and determined by the ratio of sampling rate to sample block size.

Core Module

One of Data Acquisition, Signal Processing, and User Application Module. These are called core modules because they are involved in on-line processing, as opposed to the Operator Module, which controls operation, and passively displays data sent by core modules, but is not actively involved in processing.

Parameter

A system-wide setting that is constant during a run. Parameters may be of varying type (numeric, string, etc.) and shape (single-valued, list, matrix).

State

A system-wide variable similar to what in other data acquisition applications is often called "event marker." State variables reflect important events during real-time system operation, and are saved to the data file along with each sample. In the current version of BCI2000, the temporal resolution of the state variables is limited to a sample block, i.e., state variables cannot change during a sample block.

Module

A single executable that may act as Operator Module or one of the Core Modules.

Operator Module

The experimenter's user interface, from which the system is configured, started, and stopped.

Visualization

A core module may send information into a display window maintained by the operator module. Visualization data may be of type text, signal, or graphic.

State Vector

A data structure that contains all states concatenated into a single bit string. The state vector is transmitted between modules once for each sample block, but a copy is saved with each sample of data.

Control Signal

The output of the signal processing module. When the Normalizer Filter is used, this signal has zero mean and unit variance.

Source Signal

The signal that is acquired from hardware by the ADC filter, and recorded into the data file. The TransmissionFilter reduces the source signal to a user-defined subset of channels to reduce processing load in the on-line system.