Audio Filters - WIP

A collection of filters for real-time audio processing

The overall design is in progress, there can be frequent (usually minor) breaking changes.

Feature Progress

• [x] #![no_std] (via libm)
• [x] f32 & f64 capable (via num-traits)
• [ ] SIMD (Some experimental support)
• [ ] Documentation
• [ ] Tests

Filter Types

• [x] Bell
• [x] Low Pass
• [x] High Pass
• [x] Low Shelf
• [x] High Shelf
• [x] Notch
• [x] Band Pass
• [x] All Pass
• [ ] Higher Order Bell
• [ ] Higher Order Band Pass
• [ ] Asymmetrical
• [ ] Tilt
• [ ] Flat Tilt

Filter Features

• [x] Bode Plot (phase & amplitude)
• [x] 1st and 2nd order filter primitives
• [x] Higher orders via cascading
• [x] Virtual analog (VA) State Variable Filters (SVF) for both 1st & 2nd order IIR.
• [x] Linkwitz-Riley filters
• [ ] Elliptic filters
• [ ] Phase aligned crossovers
• [ ] Decramping near nyquist
• [x] Minimum Phase IIR Mode
• [ ] Linear Phase Mode

let sample_rate_hz = 48000.0;
let cutoff_hz = 1000.0;
let gain_db = 6.0;
let width_oct = 1.0;
let order = 4.0;

let coeffs = FilterBandCoefficients::highshelf(cutoff_hz, gain_db, width_oct, order, sample_rate_hz);

let mut filter_left = FilterBand::from(&coeffs);
let mut filter_right = FilterBand::from(&coeffs);

for i in 0..1000 {
    left[i] = (filter_left.process)(&mut filter_left, left[i]);
    right[i] = (filter_right.process)(&mut filter_right, right[i]);
}