Tom RustDSP

gistfile1.rs

#[derive(Debug, Clone)]
pub struct Biquad{
    /* https://ccrma.stanford.edu/~jos/fp/Direct_Form_II.html */
    b0: f64,
    b1: f64,
    b2: f64,
    a1: f64,
    a2: f64,
}

#[derive(Debug, Clone, Default)]
pub struct BiquadState {
    vn: f64,
    vn_1: f64, //previous input sample
    vn_2: f64, //previous+1 input sample
}

impl BiquadState {
    fn update_vn(&mut self, vn: f64) {
         self.vn_2 = self.vn_1;
         self.vn_1 = self.vn;
         self.vn = vn;
    }
}

fn main() {
    println!("Hello, world!");

    let b = (0.29287490, 0.58574979, 0.29287490);
    let a = (-7.17336609e-17, 0.17149959);
    let filt1 = Biquad::new(b, a);
    
    let mut state = BiquadState::default();

    let values = vec![0.5, 0.5, 0.5, 0.5, 0.5, 0.0, 0.0, 0.0, 0.0, 0.0];

    for sample in values{
        let out = filt1.update(sample, &mut state);
        println!("value {}", out.output(&state));
    }


}


impl Biquad {

    fn new(b: (f64, f64, f64), a: (f64, f64))->Biquad {
        Biquad{b0: b.0, b1: b.1, b2: b.2, a1: a.0, a2: a.1}
    }


    fn push_sample(&self, xn: f64, state: &mut BiquadState) {
        //pass a new value into the filter. vn_2 takes value of vn_1
             
        state.update_vn(n-self.a1*state.vn_1-self.a2*state.vn_2);

    }

    fn output(&self, state: &BiquadState) -> f64 {
        self.b0*state.vn + self.b1*state.vn_1+self.b2*state.vn_2;
    }
}