bass-foundry/plugins/lathe/core/tests/dsp.rs

use common_dsp::meter::HarmonicMeter;
use common_dsp::Saw;
use lathe_core::{Engine, Settings, Source};

const RATE: f32 = 48000.;

fn engine(s: Settings) -> (Engine, usize) {
    let mut e = Engine::new(RATE, 2).unwrap();
    e.set_settings(s).unwrap();
    let l = e.latency_samples() as usize;
    (e, l)
}
fn saw(hz: f32, seconds: f32, amp: f32) -> Vec<f32> {
    let mut s = Saw::new(RATE, hz);
    (0..(seconds * RATE) as usize)
        .map(|_| s.sample() * amp)
        .collect()
}
fn render(e: &mut Engine, x: &[f32]) -> Vec<f32> {
    x.iter().map(|&v| e.process_sample([v, v])[0]).collect()
}
/// Harmonic levels of the last complete window of `x`.
fn harmonics(x: &[f32], hz: f32) -> [f32; 32] {
    let mut m = HarmonicMeter::new(RATE, 85.);
    for &v in x {
        m.push(v, hz);
    }
    *m.levels()
}

#[test]
fn a_cut_on_harmonic_three_stays_on_harmonic_three_on_every_note() {
    let mut s = Settings::default();
    s.gains[2] = -12.;
    for hz in [43.65, 65.41, 130.81] {
        let x = saw(hz, 1., 0.5);
        let (mut e, l) = engine(s);
        let y = render(&mut e, &x);
        let a = harmonics(&x[..x.len() - l], hz);
        let b = harmonics(&y[l..], hz);
        let d: Vec<f32> = (0..6).map(|k| b[k] - a[k]).collect();
        assert!((d[2] + 12.).abs() < 0.7, "{hz}: {d:?}");
        for k in [0, 1, 3, 4] {
            assert!(d[k].abs() < 1., "{hz} harmonic {}: {d:?}", k + 1);
        }
    }
}

#[test]
fn a_flat_map_passes_the_delayed_input_exactly() {
    let x = saw(55., 0.5, 0.5);
    let (mut e, l) = engine(Settings::default());
    let y = render(&mut e, &x);
    for i in l..x.len() {
        assert_eq!(y[i], x[i - l]);
    }
}

#[test]
fn odd_even_balances_the_harmonic_series() {
    let s = Settings {
        odd_even: 6.,
        ..Settings::default()
    };
    let hz = 55.;
    let x = saw(hz, 1., 0.5);
    let (mut e, l) = engine(s);
    let y = render(&mut e, &x);
    let a = harmonics(&x[..x.len() - l], hz);
    let b = harmonics(&y[l..], hz);
    for k in 1..8 {
        let want = if k % 2 == 1 { 3. } else { -3. };
        let got = b[k - 1] - a[k - 1];
        assert!((got - want).abs() < 0.8, "harmonic {k}: {got}");
    }
}

#[test]
fn note_changes_do_not_click() {
    let mut s = Settings::default();
    s.gains[1] = 12.;
    s.gains[3] = -24.;
    s.tilt = -3.;
    let mut x = saw(43.65, 0.5, 0.5);
    x.extend(saw(58.27, 0.5, 0.5));
    x.extend(saw(87.31, 0.5, 0.5));
    let (mut e, _) = engine(s);
    let y = render(&mut e, &x);
    let step = y
        .windows(2)
        .map(|w| (w[1] - w[0]).abs())
        .fold(0f32, f32::max);
    let in_step = x
        .windows(2)
        .map(|w| (w[1] - w[0]).abs())
        .fold(0f32, f32::max);
    assert!(y.iter().all(|v| v.is_finite()));
    // A saw has its own jumps; the filtered output must not jump much further than that.
    assert!(step < 2. * in_step, "{step} vs {in_step}");
}

#[test]
fn midi_source_tunes_the_bands_at_the_delayed_note_time() {
    let mut s = Settings {
        source: Source::Midi,
        ..Settings::default()
    };
    s.gains[0] = -24.;
    let (mut e, l) = engine(s);
    // 43.65 Hz is MIDI 29. Notes arrive at sample 0; the bands must be tuned by sample l.
    e.note_on(29);
    let x = saw(43.65, 1., 0.5);
    let y = render(&mut e, &x);
    let a = harmonics(&x[..x.len() - l], 43.65);
    let b = harmonics(&y[l..], 43.65);
    assert!(b[0] - a[0] < -20., "{}", b[0] - a[0]);
    let f = e.take_analyzer();
    assert_eq!(f.note, Some(29));
    assert!((f.hz - 43.65).abs() < 0.05);
}

#[test]
fn settings_are_validated_and_serialise() {
    let s = Settings::default();
    let json = serde_json::to_string(&s).unwrap();
    assert_eq!(serde_json::from_str::<Settings>(&json).unwrap(), s);
    let mut bad = s;
    bad.gains[5] = 40.;
    assert!(bad.validate().is_err());
    bad = s;
    bad.harmonics = 4;
    assert!(bad.validate().is_err());
    bad = s;
    bad.width = f32::NAN;
    assert!(bad.validate().is_err());
    let mut e = Engine::new(RATE, 2).unwrap();
    assert!(e.set_settings(bad).is_err());
    assert_eq!(e.settings(), s);
}