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

use common_dsp::meter::HarmonicMeter;
use common_dsp::Saw;
use std::f32::consts::TAU;
use temper_core::{Curve, 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()
}
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()
}
/// Harmonics 1–n relative to the fundamental.
fn profile(x: &[f32], hz: f32, n: usize) -> Vec<f32> {
    let h = harmonics(x, hz);
    (0..n).map(|k| h[k] - h[0]).collect()
}
fn rms_db(x: &[f32]) -> f32 {
    10. * (x.iter().map(|v| v * v).sum::<f32>() / x.len() as f32).log10()
}

#[test]
fn quiet_and_loud_patches_distort_the_same() {
    let s = Settings {
        drive: 18.,
        auto_gain: false,
        ..Settings::default()
    };
    let mut profiles = vec![];
    for amp in [0.5, 0.06] {
        let (mut e, _) = engine(s);
        let y = render(&mut e, &saw(55., 1.2, amp));
        profiles.push(profile(&y[y.len() / 2..], 55., 8));
    }
    for k in 1..8 {
        let d = profiles[0][k] - profiles[1][k];
        assert!(d.abs() < 1., "harmonic {}: {profiles:?}", k + 1);
    }
    // Without normalisation the quiet patch is barely distorted.
    let s = Settings { normalize: 0., ..s };
    let (mut e, _) = engine(s);
    let y = render(&mut e, &saw(55., 1.2, 0.06));
    let quiet = profile(&y[y.len() / 2..], 55., 8);
    assert!(
        (quiet[2] - profiles[0][2]).abs() > 2.,
        "{quiet:?} vs {profiles:?}"
    );
}

#[test]
fn bright_follows_the_note() {
    let s = Settings {
        drive: 24.,
        curve: Curve::Hard,
        bright: 8.,
        ..Settings::default()
    };
    let mut profiles = vec![];
    for hz in [43.65, 87.31] {
        let (mut e, _) = engine(s);
        let y = render(&mut e, &saw(hz, 1.2, 0.4));
        profiles.push(profile(&y[y.len() / 2..], hz, 14));
    }
    for k in 1..14 {
        let d = profiles[0][k] - profiles[1][k];
        assert!(d.abs() < 1.5, "harmonic {}: {profiles:?}", k + 1);
    }
    // Above the cutoff the harmonics fall away on both notes.
    assert!(profiles[0][12] < profiles[0][4] - 10.);
}

/// Energy away from the harmonics of `hz`, relative to the harmonics, in dB.
fn alias_ratio(curve: Curve, drive: f32, hz: f32) -> f32 {
    let s = Settings {
        drive,
        curve,
        auto_gain: false,
        ..Settings::default()
    };
    let (mut e, _) = engine(s);
    let x: Vec<f32> = (0..36000)
        .map(|i| 0.3 * (TAU * hz * i as f32 / RATE).sin())
        .collect();
    let y = render(&mut e, &x);
    let tail = &y[12000..];
    let n = tail.len();
    let window: Vec<f32> = (0..n)
        .map(|i| 0.5 - 0.5 * (TAU * i as f32 / n as f32).cos())
        .collect();
    let (mut harmonic, mut other) = (0f64, 0f64);
    for f in (20..23000).step_by(10) {
        // Goertzel power at f.
        let c = 2. * (TAU as f64 * f as f64 / RATE as f64).cos();
        let (mut s1, mut s2) = (0f64, 0f64);
        for (v, w) in tail.iter().zip(&window) {
            let s0 = (v * w) as f64 + c * s1 - s2;
            s2 = s1;
            s1 = s0;
        }
        let p = s1 * s1 + s2 * s2 - c * s1 * s2;
        let near = (f as f32 / hz - (f as f32 / hz).round()).abs() * hz < 30.;
        if near {
            harmonic += p;
        } else {
            other += p;
        }
    }
    (10. * (other / harmonic).log10()) as f32
}

#[test]
fn oversampling_keeps_aliasing_down_in_the_bass_range() {
    // 2 kHz stands for the upper harmonics of a growl, 440 Hz for a high bass fundamental.
    for curve in Curve::ALL {
        let r = alias_ratio(curve, 24., 2000.);
        assert!(r < -60., "{} 2 kHz: {r}", curve.name());
        let r = alias_ratio(curve, 36., 440.);
        assert!(r < -55., "{} 440 Hz: {r}", curve.name());
    }
}

#[test]
#[ignore]
fn print_alias_ratios() {
    for curve in Curve::ALL {
        for hz in [440., 2000., 5000.] {
            for drive in [12., 24., 36.] {
                println!(
                    "{} {hz} {drive}: {:.1}",
                    curve.name(),
                    alias_ratio(curve, drive, hz)
                );
            }
        }
    }
}

#[test]
fn auto_gain_matches_input_loudness() {
    for drive in [6., 24., 36.] {
        let s = Settings {
            drive,
            ..Settings::default()
        };
        let (mut e, l) = engine(s);
        let x = saw(55., 2., 0.3);
        let y = render(&mut e, &x);
        let d = rms_db(&y[y.len() / 2..]) - rms_db(&x[x.len() / 2 - l..x.len() - l]);
        assert!(d.abs() < 1., "{drive}: {d}");
    }
}

#[test]
fn zero_mix_is_the_delayed_dry_signal_and_latency_is_exact() {
    let s = Settings {
        mix: 0.,
        ..Settings::default()
    };
    let (mut e, l) = engine(s);
    let x = saw(55., 1., 0.5);
    let y = render(&mut e, &x);
    for i in RATE as usize / 2..x.len() {
        assert_eq!(y[i], x[i - l], "{i}");
    }
    // With the shaper nearly linear the wet path lines up with the dry one.
    let s = Settings {
        drive: 0.,
        normalize: 0.,
        curve: Curve::Soft,
        auto_gain: false,
        ..Settings::default()
    };
    let (mut e, l) = engine(s);
    let mut x = vec![0f32; 9600];
    x[100] = 0.01;
    let y = render(&mut e, &x);
    let at = y
        .iter()
        .enumerate()
        .max_by(|a, b| a.1.abs().total_cmp(&b.1.abs()))
        .unwrap()
        .0;
    assert_eq!(at, 100 + l);
}

#[test]
fn midi_source_tunes_filters_at_the_delayed_note_time() {
    let s = Settings {
        source: Source::Midi,
        bright: 4.,
        drive: 18.,
        curve: Curve::Hard,
        ..Settings::default()
    };
    let (mut e, _) = engine(s);
    e.note_on(29);
    let y = render(&mut e, &saw(43.65, 1., 0.4));
    let p = profile(&y[y.len() / 2..], 43.65, 12);
    assert!(p[10] < p[2] - 12., "{p:?}");
    let f = e.take_analyzer();
    assert_eq!(f.note, Some(29));
}

#[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);
    for bad in [
        Settings { floor: 0.1, ..s },
        Settings { bright: 2., ..s },
        Settings {
            push_harmonic: 0,
            ..s
        },
        Settings {
            drive: f32::NAN,
            ..s
        },
    ] {
        assert!(bad.validate().is_err(), "{bad:?}");
    }
    for c in Curve::ALL {
        assert_eq!(c.shape(0.), 0.);
        assert!(c.shape(100.).abs() <= 1.0001);
    }
}