User Reference:Data File Formats

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This page describes which data formats are available for output, and how to select amongst them.

General Information

Support for various output formats is provided by File Writer classes (modules) descending from GenericFileWriter. At runtime, selection of a file format is achieved by specifying a command line parameter to the source module, as in

DASSource --FileFormat-Null

or

RandomNumber --FileFormat-GDF

Typically, source modules are launched from batch files contained in the batch directory, and their command line parameters are specified there.

The value following the last minus character, appended with FileWriter, will be matched against the names of all GenericFileWriter descendants present in the source module. In the first example, the NullFileWriter class will be used for data output (which will not produce any output file), and the GDFFileWriter class will be used in the second example.

BCI2000 File Format

--FileFormat-BCI2000

Parameters, BCI2000 state variables, and brain signal data will be written into a BCI2000 data file as defined in the BCI2000 specification. This is also the default if no file format is specified explicitly.

Null File Format

--FileFormat-Null

No information is recorded. Individual filters may still write log files to the directory defined by the FileInitials, SubjectName, and SubjectSession parameters.

EDF File Format

--FileFormat-EDF

EDF (European Data Format) is a standard for biosignal data especially popular in the area of sleep research.

  • EDF is limited to 16 bit data.
  • BCI2000 state variables will be mapped to additional signal channels that contain a single sample for each data block.
  • BCI2000 parameters cannot be represented in EDF format. Setting the SaveAdditionalParameterFile parameter to 1 will save a separate BCI2000 parameter file along with the EDF data file.

References

  • Bob Kemp, Alpo Värri, Agostinho C. Rosa, Kim D. Nielsen and John Gade, A simple format for exchange of digitized polygraphic recordings, Electroencephalography and Clinical Neurophysiology, 82 (1992), pp 391-393.
  • EDF home page at http://www.hsr.nl/edf/

GDF File Format

--FileFormat-GDF

GDF is a general data format for biosignals which is popular in BCI research. Building on EDF, GDF allows for arbitrary numeric data types, introduces an event table, and provides standardized encoding of events.

  • Currently, BCI2000 supports Version 1.25 of the GDF format specification.
  • BCI2000 does not prescribe the semantics of its state variables. GDF, on the other hand, associates a fixed set of events with certain numeric codes. Thus, a general mapping of BCI2000 states onto GDF events is not possible. Instead, GDF events are created via a user-defined set of mapping rules in the EventCode parameter, which also has a set of rules predefined for the most important cases.
  • Besides GDF events, BCI2000 state variables will also be mapped to additional signal channels the same way as for EDF.
  • BCI2000 parameters cannot be represented in GDF format. Setting the SaveAdditionalParameterFile parameter to 1 will save a separate BCI2000 parameter file along with the GDF data file.

References