Filtering of C3D data

Main Forum
1

Hi,

I was just wondering what this piece of code is doing exactly (from ModelSetup.any):

 Filter =  {
    N = 2;
    Fc = {5};
    Type = LowPass;
  };
  
  /// This filter is used for the analog data
  AnyFunButterworthFilter LowPassFilter = {
    FilterForwardBackwardOnOff = On;
    AutomaticInitialConditionOnOff = On;
    N = 2;
    AnyVar CutOffFrequency=12;
    AnyVar SampleFreq=.Header.VideoFrameRate*.Header.NoAnalogSamplesPer3DFrame   ;
    W = {1/(SampleFreq*0.5)*CutOffFrequency};
    Type = LowPass;
  };

I understand that a Butterworth filter is used for the analog data, but what I don’t see is why there are two sections for this filter, shouldn’t one be enough?

Best regards,
Patrick

2

Hi,

The first(index 0) filter is used for the markers in the C3D file.

For instance, you can see that the following two values are different:
Main.ModelSetup.C3DFileData.Points.Markers.RASI.Pos
Main.ModelSetup.C3DFileData.Points.Markers.RASI.PosFiltered

Best regards,
Moonki

1 Like
3

OK, thank for your help.