iir lowpass: f32 is sufficient
This commit is contained in:
parent
73c98c947a
commit
7c1fa9695a
@ -1,4 +1,4 @@
|
||||
use core::f64::consts::PI;
|
||||
use core::f32::consts::PI;
|
||||
use serde::{Deserialize, Serialize};
|
||||
|
||||
/// Generic vector for integer IIR filter.
|
||||
@ -19,14 +19,14 @@ impl IIRState {
|
||||
///
|
||||
/// # Returns
|
||||
/// 2nd-order IIR filter coefficients in the form [b0,b1,b2,a1,a2]. a0 is set to -1.
|
||||
pub fn lowpass(f: f64, q: f64, k: f64) -> IIRState {
|
||||
pub fn lowpass(f: f32, q: f32, k: f32) -> IIRState {
|
||||
// 3rd order Taylor approximation of sin and cos.
|
||||
let f = f * 2. * PI;
|
||||
let fsin = f - f * f * f / 6.;
|
||||
let fcos = 1. - f * f / 2.;
|
||||
let alpha = fsin / (2. * q);
|
||||
// IIR uses Q2.30 fixed point
|
||||
let a0 = (1. + alpha) / (1 << IIR::SHIFT) as f64;
|
||||
let a0 = (1. + alpha) / (1 << IIR::SHIFT) as f32;
|
||||
let b0 = (k / 2. * (1. - fcos) / a0) as _;
|
||||
let a1 = (2. * fcos / a0) as _;
|
||||
let a2 = ((alpha - 1.) / a0) as _;
|
||||
@ -96,7 +96,7 @@ mod test {
|
||||
|
||||
#[test]
|
||||
fn lowpass_gen() {
|
||||
let ba = IIRState::lowpass(1e-3, 1. / 2f64.sqrt(), 2.);
|
||||
let ba = IIRState::lowpass(1e-3, 1. / 2f32.sqrt(), 2.);
|
||||
println!("{:?}", ba.0);
|
||||
}
|
||||
}
|
||||
|
Loading…
Reference in New Issue
Block a user