dplug ~master (2018-10-30T21:29:54Z)

- BiquadCoeffalias BiquadCoeff =
`double[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.

- biquadBypass
`BiquadCoeff`biquadBypass`()` Identity biquad, pass signal unchanged.

- biquadOnePoleHighPass
`BiquadCoeff`biquadOnePoleHighPass`(double frequency, double sampleRate)` 1-pole high-pass filter. Note: the cutoff frequency can be >= nyquist, in which case it is equal to zero. the cutoff frequency can be below 0 Hz, in which case it asymptotically approaches a bypass. You always have -3 dB at cutoff in the valid range.

- 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.

- biquadOnePoleLowPass
`BiquadCoeff`biquadOnePoleLowPass`(double frequency, double sampleRate)` 1-pole low-pass filter. Note: the cutoff frequency can be >= nyquist, in which case it asymptotically approaches a bypass. the cutoff frequency can be below 0 Hz, in which case it is equal to zero. You always have -3 dB at cutoff in the valid range.

- 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 = SQRT1_2)` Band-pass filter as described by Robert Bristow-Johnson.

- biquadRBJHighPass
`BiquadCoeff`biquadRBJHighPass`(double frequency, double samplerate, double Q = SQRT1_2)` High-pass filter 12 dB/oct as described by Robert Bristow-Johnson.

- biquadRBJHighShelf
`BiquadCoeff`biquadRBJHighShelf`(double frequency, double samplerate, double gain, double Q = SQRT1_2)` High-shelf filter as described by Robert Bristow-Johnson.

- biquadRBJLowPass
`BiquadCoeff`biquadRBJLowPass`(double frequency, double samplerate, double Q = SQRT1_2)` Low-pass filter 12 dB/oct as described by Robert Bristow-Johnson.

- biquadRBJLowShelf
`BiquadCoeff`biquadRBJLowShelf`(double frequency, double samplerate, double gain, double Q = SQRT1_2)` Low-shelf filter as described by Robert Bristow-Johnson.

- biquadRBJNotch
`BiquadCoeff`biquadRBJNotch`(double frequency, double samplerate, double Q = SQRT1_2)` Notch filter as described by Robert Bristow-Johnson.

- biquadRBJPeak
`BiquadCoeff`biquadRBJPeak`(double frequency, double samplerate, double gain, double Q = SQRT1_2)` Peak filter as described by Robert Bristow-Johnson.

- biquadZero
`BiquadCoeff`biquadZero`()` Zero biquad, gives zero output.

- BiquadDelaystruct BiquadDelay
Maintain state for a biquad state. A biquad is a realization that can model two poles and two zeros.

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