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iir_int: use f64 for extreme filters

This commit is contained in:
Robert Jördens 2021-02-04 15:21:05 +01:00
parent 8314844aeb
commit 473bdaa9bc
1 changed files with 4 additions and 4 deletions
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8
dsp/src/iir_int.rs
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@ -1,4 +1,4 @@
use core::f32::consts::PI;
use core::f64::consts::PI;
use serde::{Deserialize, Serialize};
/// Generic vector for integer IIR filter.
@ -19,7 +19,7 @@ impl Vec5 {
///
/// # Returns
/// 2nd-order IIR filter coefficients in the form [b0,b1,b2,a1,a2]. a0 is set to -1.
pub fn lowpass(f: f32, q: f32, k: f32) -> Self {
pub fn lowpass(f: f64, q: f64, k: f64) -> Self {
// 3rd order Taylor approximation of sin and cos.
let f = f * 2. * PI;
let f2 = f * f * 0.5;
@ -27,7 +27,7 @@ impl Vec5 {
let fsin = f * (1. - f2 / 3.);
let alpha = fsin / (2. * q);
// IIR uses Q2.30 fixed point
let a0 = (1. + alpha) / (1 << IIR::SHIFT) as f32;
let a0 = (1. + alpha) / (1 << IIR::SHIFT) as f64;
let b0 = (k / 2. * (1. - fcos) / a0) as _;
let a1 = (2. * fcos / a0) as _;
let a2 = ((alpha - 1.) / a0) as _;
@ -97,7 +97,7 @@ mod test {
#[test]
fn lowpass_gen() {
let ba = Vec5::lowpass(1e-3, 1. / 2f32.sqrt(), 2.);
let ba = Vec5::lowpass(1e-5, 1. / 2f64.sqrt(), 2e5);
println!("{:?}", ba.0);
}
}