idsp::iir

Struct Filter

pub struct Filter<T> { /* private fields */ }

Expand description

Standard audio biquad filter builder

https://www.w3.org/TR/audio-eq-cookbook/

Implementations§

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impl<T> Filter<T>
where T: 'static + Float + FloatConst, f32: AsPrimitive<T>,

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pub fn frequency( &mut self, critical_frequency: T, sample_frequency: T, ) -> &mut Self

Set crititcal frequency from absolute units.

§Arguments

critical_frequency: “Relevant” or “corner” or “center” frequency in the same units as sample_frequency
sample_frequency: The sample frequency in the same units as critical_frequency. E.g. both in SI Hertz or rad/s.

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pub fn critical_frequency(&mut self, f0: T) -> &mut Self

Set relative critical frequency

§Arguments

f0: Relative critical frequency in units of the sample frequency. Must be 0 <= f0 <= 0.5.

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pub fn angular_critical_frequency(&mut self, w0: T) -> &mut Self

Set relative critical angular frequency

§Arguments

w0: Relative critical angular frequency. Must be 0 <= w0 <= π. Defaults to 0.0.

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pub fn gain(&mut self, k: T) -> &mut Self

Set reference gain

§Arguments

k: Linear reference gain. Defaults to 1.0.

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pub fn gain_db(&mut self, k_db: T) -> &mut Self

Set reference gain in dB

§Arguments

k_db: Reference gain in dB. Defaults to 0.0.

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pub fn shelf(&mut self, a: T) -> &mut Self

Set linear shelf gain

Used only for peaking, highshelf, lowshelf filters.

§Arguments

a: Linear shelf gain. Defaults to 1.0.

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pub fn shelf_db(&mut self, a_db: T) -> &mut Self

Set shelf gain in dB

Used only for peaking, highshelf, lowshelf filters.

§Arguments

a_db: Linear shelf gain. Defaults to 0.0.

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pub fn inverse_q(&mut self, qi: T) -> &mut Self

Set inverse Q parameter of the filter

The inverse “steepness”/“narrowness” of the filter transition. Defaults sqrt(2) which is as steep as possible without overshoot.

§Arguments

qi: Inverse Q parameter.

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pub fn q(&mut self, q: T) -> &mut Self

Set Q parameter of the filter

The “steepness”/“narrowness” of the filter transition. Defaults 1/sqrt(2) which is as steep as possible without overshoot.

This affects the same parameter as bandwidth() and shelf_slope(). Use only one of them.

§Arguments

q: Q parameter.

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pub fn bandwidth(&mut self, bw: T) -> &mut Self

Set the relative bandwidth

This affects the same parameter as inverse_q() and shelf_slope(). Use only one of them.

§Arguments

bw: Bandwidth in octaves

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pub fn shelf_slope(&mut self, s: T) -> &mut Self

Set the shelf slope.

This affects the same parameter as inverse_q() and bandwidth(). Use only one of them.

§Arguments

s: Shelf slope. A slope of 1.0 is maximally steep without overshoot.

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pub fn lowpass(&self) -> [T; 6]

Low pass filter

Builds second order biquad low pass filter coefficients.

use idsp::iir::*;
let ba = Filter::default()
    .critical_frequency(0.1)
    .gain(1000.0)
    .lowpass();
let iir = Biquad::<i32>::from(&ba);
let mut xy = [0; 4];
let x = vec![3, -4, 5, 7, -3, 2];
let y: Vec<_> = x.iter().map(|x0| iir.update(&mut xy, *x0)).collect();
assert_eq!(y, [5, 3, 9, 25, 42, 49]);

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pub fn highpass(&self) -> [T; 6]

High pass filter

Builds second order biquad high pass filter coefficients.

use idsp::iir::*;
let ba = Filter::default()
    .critical_frequency(0.1)
    .gain(1000.0)
    .highpass();
let iir = Biquad::<i32>::from(&ba);
let mut xy = [0; 4];
let x = vec![3, -4, 5, 7, -3, 2];
let y: Vec<_> = x.iter().map(|x0| iir.update(&mut xy, *x0)).collect();
assert_eq!(y, [5, -9, 11, 12, -1, 17]);

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pub fn bandpass(&self) -> [T; 6]

Band pass

use idsp::iir::*;
let ba = Filter::default()
    .frequency(1000.0, 48e3)
    .q(5.0)
    .gain_db(3.0)
    .bandpass();
println!("{ba:?}");

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pub fn notch(&self) -> [T; 6]

A notch filter

Has zero gain at the critical frequency.

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pub fn allpass(&self) -> [T; 6]

An allpass filter

Has constant gain at all frequency but a variable phase shift.

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pub fn peaking(&self) -> [T; 6]

A peaking/dip filter

Has gain*shelf_gain at critical frequency and gain elsewhere.

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pub fn lowshelf(&self) -> [T; 6]

Low shelf

Approaches gain*shelf_gain below critical frequency and gain above.

use idsp::iir::*;
let ba = Filter::default()
    .frequency(1000.0, 48e3)
    .shelf_slope(2.0)
    .shelf_db(20.0)
    .lowshelf();
println!("{ba:?}");

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