dplug.dsp.iir

Basic IIR 1-pole and 2-pole filters through biquads.

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Aliases

BiquadCoeff alias BiquadCoeff = float[5]: Type which hold the biquad coefficients. Important: Coefficients are considered always normalized by a0. Note: coeff[0] is b0, coeff[1] is b1, coeff[2] is b2, coeff[3] is a1, coeff[4] is a2 in the litterature.

Functions

allpassThiran1stOrder BiquadCoeff allpassThiran1stOrder(double fractionalDelay): Allpass interpolator. https://ccrma.stanford.edu/~jos/pasp/First_Order_Allpass_Interpolation.html http://users.spa.aalto.fi/vpv/publications/vesan_vaitos/ch3_pt3_allpass.pdf
It is recommended to use the range [0.5 .. 1.5] for best phase results. Also known as Thiran filter.
allpassThiran2ndOrder BiquadCoeff allpassThiran2ndOrder(double fractionalDelay): Same but 2nd order. http://users.spa.aalto.fi/vpv/publications/vesan_vaitos/ch3_pt3_allpass.pdf
biquadBypass BiquadCoeff biquadBypass(): Identity biquad, pass signal unchanged.
biquadOnePoleHighPassImprecise BiquadCoeff biquadOnePoleHighPassImprecise(double frequency, double samplerate): 1-pole high-pass filter, frequency mapping is not precise. Not accurate across sample rates, but coefficient computation is cheap. Not advised.
biquadOnePoleLowPassImprecise BiquadCoeff biquadOnePoleLowPassImprecise(double frequency, double samplerate): 1-pole low-pass filter, frequency mapping is not precise. Not accurate across sample rates, but coefficient computation is cheap. Not advised.
biquadRBJBandPass BiquadCoeff biquadRBJBandPass(double frequency, double samplerate, double Q): Band-pass filter as described by Robert Bristow-Johnson.
biquadRBJHighPass BiquadCoeff biquadRBJHighPass(double frequency, double samplerate, double Q): High-pass filter 12 dB/oct as described by Robert Bristow-Johnson.
biquadRBJHighShelf BiquadCoeff biquadRBJHighShelf(double frequency, double samplerate, double gain, double Q): High-shelf filter as described by Robert Bristow-Johnson.
biquadRBJLowPass BiquadCoeff biquadRBJLowPass(double frequency, double samplerate, double Q): Low-pass filter 12 dB/oct as described by Robert Bristow-Johnson.
biquadRBJLowShelf BiquadCoeff biquadRBJLowShelf(double frequency, double samplerate, double gain, double Q): Low-shelf filter as described by Robert Bristow-Johnson.
biquadRBJNotch BiquadCoeff biquadRBJNotch(double frequency, double samplerate, double Q): Notch filter as described by Robert Bristow-Johnson.
biquadRBJPeak BiquadCoeff biquadRBJPeak(double frequency, double samplerate, double gain, double Q): Peak filter as described by Robert Bristow-Johnson.
biquadZero BiquadCoeff biquadZero(): Zero biquad, gives zero output.

Structs

BiquadDelay struct BiquadDelay: Maintain state for a biquad state. To use an IIR filter you need an IIRDelay + one IIRCoeff.

dplug.dsp.iir

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