index :: flt

flt.c_apf

aliases: [ceammc/apf->biquad], [apf->biquad]

Allpass filter coefficient calculator for biquad

available since version: 0.9.2

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information

Allpass filter is a signal processing filter that passes all frequencies equally in gain, but changes the phase relationship among various frequencies. Most types of filter reduce the amplitude (i.e. the magnitude) of the signal applied to it for some values of frequency, whereas the all-pass filter allows all frequencies through without changes in level. Calculates coefficients for transfer function: H(z)=(b0 + b1z⁻¹ + b2z⁻²)/(1 + a1z⁻¹ + a2z⁻²)

arguments:

• FREQ center frequency
  type: float
  units: Hz
  

methods:

• bw set bandwidth in octaves
  parameters:
  • OCT bandwidth
    type: float
    required: True
    

properties:

• @freq Get/set center frequency
  type: float
  units: Hz
  range: 0..22050
  default: 0
  

• @q Get/set quality factor: @freq/BANDWIDTH
  type: float
  range: 0.01..100
  default: 0.7071
  

• @rad (initonly) Get/set use angular frequency
  type: flag
  

inlets:

• filter frequency
  type: control

outlets:

• list: b0 b1 b2 a1 a2
  type: control

keywords:

filter biquad hpf allpass

See also: [flt.c_lpf] [hilbert~]

Authors: Serge Poltavsky

License: GPL3 or later