User Reference:SourceFilter

Function

Most EEG amplifiers offer filtring in hardware. Generally, they have a line noise hum filter, or "notch filter", built in, and perform some high pass filtering. For amplifiers that do not provide these filters themselves, there is the SourceFilter as a software solution.

Unlike other filters, the SourceFilter filter will be applied immediately after data acquisition, and it will modify the data which will be saved to disk, i.e., it will behave just as if it were a hardware filter built into the amplifier.

Parameters

NotchFilter

Configures the notch filter. The proper setting depends on your country.

• 0: disabled,
• 1: at 50Hz (Europe, Asia, Africa, parts of South America)
• 2: at 60Hz (North America, parts of South America).

The notch filter is realized as a 2x3rd order Chebychev bandstop.

HighPassFilter

Configures the high pass filter:

• 0: disabled,
• 1: at 0.1Hz.

The high pass filter is realized as a 1st order IIR filter.

Remarks

Generally, the SourceFilter will be available in source modules connecting to amplifiers that require it. Adding the SourceFilter to modules that do not yet contain it requires recompilation.

To add the SourceFilter to a new or existing source module, add the following files to the project, and recompile:

BCI2000/src/shared/modules/signalsource/SourceFilter.cpp
                          /signalprocessing/IIRFilter.cpp
                                            FilterDesign.cpp

See also

User Reference:Filters, Programming Reference:Compiling BCI2000