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

use forge_core::{Engine, Settings, Source, Stage, ORDERS};

const RATE: f32 = 48000.;

/// A bassline of saw notes with gaps, a different pitch each, at A1 to A2.
fn bass(i: usize) -> [f32; 2] {
    let note = [33., 40., 36., 45., 38.][(i / 14400) % 5];
    let hz = 440. * 2f64.powf((note - 69.) / 12.);
    let t = i as f64 / RATE as f64;
    let on = i % 14400 < 12000;
    let v = if on {
        (0.4 * (2. * (hz * t).fract() - 1.)) as f32
    } else {
        0.
    };
    [v, 0.8 * v]
}

/// Module settings that change the sound, so a mismatch would show.
fn shaped() -> Settings {
    let mut s = Settings::default();
    s.lathe.gains[2] = -12.;
    s.lathe.tilt = -3.;
    s.temper.drive = 12.;
    s.temper.bias = 20.;
    s.temper.push_gain = 6.;
    s.temper.bright = 8.;
    s.knurl.apply_pattern(&[0., -9.]);
    s.knurl.time_jitter = 6.;
    s.knurl.level_jitter = 2.;
    s.knurl.grit = -18.;
    s
}

fn only(stage: Stage, order: [Stage; 3]) -> Settings {
    let mut s = shaped();
    s.order = order;
    for st in Stage::ALL {
        s.set_on(st, st == stage);
    }
    s
}

/// One module on its own in the strip sounds exactly like its standalone plugin, in every
/// position: the strip's tracker and note timing are the plugin's.
#[test]
fn each_module_alone_matches_its_standalone_plugin() {
    let n = 80000;
    for order in ORDERS {
        for stage in Stage::ALL {
            let s = only(stage, order);
            let mut forge = Engine::new(RATE, 2).unwrap();
            forge.set_settings(s).unwrap();
            let (alone, latency): (Vec<[f32; 2]>, u32) = match stage {
                Stage::Lathe => {
                    let mut e = lathe_core::Engine::new(RATE, 2).unwrap();
                    e.set_settings(s.lathe).unwrap();
                    (
                        (0..n).map(|i| e.process_sample(bass(i))).collect(),
                        e.latency_samples(),
                    )
                }
                Stage::Temper => {
                    let mut e = temper_core::Engine::new(RATE, 2).unwrap();
                    e.set_settings(s.temper).unwrap();
                    (
                        (0..n).map(|i| e.process_sample(bass(i))).collect(),
                        e.latency_samples(),
                    )
                }
                Stage::Knurl => {
                    let mut e = knurl_core::Engine::new(RATE, 2).unwrap();
                    e.set_settings(s.knurl).unwrap();
                    (
                        (0..n).map(|i| e.process_sample(bass(i))).collect(),
                        e.latency_samples(),
                    )
                }
            };
            let strip: Vec<[f32; 2]> = (0..n).map(|i| forge.process_sample(bass(i))).collect();
            let shift = (forge.latency_samples() - latency) as usize;
            for i in 0..n - shift {
                assert_eq!(
                    strip[i + shift],
                    alone[i],
                    "{stage:?} in {order:?}, sample {i}"
                );
            }
        }
    }
}

#[test]
fn the_strip_has_one_lookahead() {
    let forge = Engine::new(RATE, 2).unwrap();
    let lathe = lathe_core::Engine::new(RATE, 2).unwrap().latency_samples();
    let temper = temper_core::Engine::new(RATE, 2).unwrap().latency_samples();
    let knurl = knurl_core::Engine::new(RATE, 2).unwrap().latency_samples();
    // Lathe has no latency of its own: its latency is the lookahead.
    let own = (temper - lathe) + (knurl - lathe);
    assert_eq!(forge.latency_samples(), lathe + own);
    let ms = |s: u32| s as f32 / RATE * 1000.;
    assert!(
        ms(forge.latency_samples()) < 75.,
        "{}",
        ms(forge.latency_samples())
    );
    assert!(ms(lathe + temper + knurl) > 200.);
    // Changing the order keeps the latency.
    let mut f = Engine::new(RATE, 2).unwrap();
    let before = f.latency_samples();
    for order in ORDERS {
        f.set_settings(Settings {
            order,
            ..Settings::default()
        })
        .unwrap();
        assert_eq!(f.latency_samples(), before);
    }
}

/// Knurl's sub-octave pattern first, then Lathe: Lathe still follows the played note, because
/// the tracker reads the strip's input. A standalone Lathe after Knurl hears the sub-octave.
#[test]
fn modules_after_knurl_follow_the_played_note() {
    let mut s = Settings {
        order: [Stage::Knurl, Stage::Lathe, Stage::Temper],
        ..Settings::default()
    };
    s.knurl.apply_pattern(&[0., -12.]);
    s.temper.bypass = true;
    let mut forge = Engine::new(RATE, 2).unwrap();
    forge.set_settings(s).unwrap();
    let mut knurl = knurl_core::Engine::new(RATE, 2).unwrap();
    knurl.set_settings(s.knurl).unwrap();
    let mut lathe = lathe_core::Engine::new(RATE, 2).unwrap();
    lathe.set_settings(s.lathe).unwrap();
    // One long note at A2 (110 Hz).
    let hz = 110.;
    let note = |i: usize| {
        let v = (0.4 * (2. * (hz * i as f64 / RATE as f64).fract() - 1.)) as f32;
        [v, v]
    };
    let (mut strip_ok, mut chain_ok, mut frames) = (0, 0, 0);
    for i in 0..96000 {
        forge.process_sample(note(i));
        lathe.process_sample(knurl.process_sample(note(i)));
        if i > 24000 && i % 480 == 0 {
            frames += 1;
            let near = |f: f32| (f / hz as f32 - 1.).abs() < 0.02;
            strip_ok += usize::from(near(forge.take_analyzer().lathe.hz));
            chain_ok += usize::from(near(lathe.take_analyzer().hz));
        }
    }
    assert_eq!(strip_ok, frames);
    assert!(chain_ok < frames / 2, "{chain_ok} of {frames}");
}

#[test]
fn bypass_is_the_input_delayed_by_the_latency() {
    let mut e = Engine::new(RATE, 2).unwrap();
    e.set_settings(Settings {
        bypass: true,
        ..shaped()
    })
    .unwrap();
    let latency = e.latency_samples() as usize;
    let out: Vec<[f32; 2]> = (0..30000).map(|i| e.process_sample(bass(i))).collect();
    for (i, o) in out.iter().enumerate().skip(latency) {
        assert_eq!(*o, bass(i - latency));
    }
}

#[test]
fn midi_notes_drive_every_module() {
    let mut s = shaped();
    s.source = Source::Midi;
    let mut e = Engine::new(RATE, 1).unwrap();
    e.set_settings(s).unwrap();
    for i in 0..24000 {
        if i == 100 {
            e.note_on(45);
        }
        e.process_sample(bass(i));
    }
    let f = e.take_analyzer();
    assert_eq!(f.note, Some(45));
    assert_eq!(f.lathe.note, Some(45));
    assert_eq!(f.temper.note, Some(45));
    assert_eq!(f.knurl.note, Some(45));
    assert_eq!(f.lathe.latency, e.latency_samples());
}

#[test]
fn settings_are_validated_and_serialise() {
    assert!(Settings::default().validate().is_ok());
    let bad = Settings {
        order: [Stage::Lathe, Stage::Lathe, Stage::Knurl],
        ..Settings::default()
    };
    assert!(bad.validate().is_err());
    assert!(Engine::new(RATE, 2).unwrap().set_settings(bad).is_err());
    let bad = Settings {
        gate: -10.,
        ..Settings::default()
    };
    assert!(bad.validate().is_err());
    let mut bad = Settings::default();
    bad.temper.drive = f32::NAN;
    assert!(bad.validate().is_err());
    let s = Settings {
        order: ORDERS[4],
        source: Source::Midi,
        ..shaped()
    };
    let json = serde_json::to_string(&s).unwrap();
    assert_eq!(serde_json::from_str::<Settings>(&json).unwrap(), s);
    assert!(serde_json::from_str::<Settings>(r#"{"gate":-40,"oops":1}"#).is_err());
}