feuerwerk/tests/core/acid.test.ts

/**
 * The Acid of an instrument (#421): a TB-303 line rendered sample by sample as its worklet does it,
 * the line that lets a note slide out of the one before, and the node that makes it.
 */
import { describe, expect, it } from 'vitest';
import { compileInstrument, instrumentSourcesOf } from '../../src/core/instrument/compile';
import { INSTRUMENT_ACID, INSTRUMENT_NOTES, INSTRUMENT_OUTPUT } from '../../src/core/instrument/nodes';
import { noteFrequency } from '../../src/core/instrument/notes';
import type { Graph } from '../../src/core/graph/Graph';
import type { PropertyBag } from '../../src/core/model/Properties';
import {
  ACCENT_VELOCITY,
  type AcidKnobs,
  AcidLine,
  type AcidNote,
  acidResponseDb,
  type AcidShape,
  AcidSynth,
} from '../../src/core/soundfx/acid';
import { fxChainOf } from '../../src/core/soundfx/nodes';
import { levelsOf } from '../../src/viewport/fxNodes';
import { makeProject } from '../helpers';

const RATE = 48000;
const BLOCK = 128;
const SAW: AcidShape = { wave: 'saw', slideTime: 0.06 };

function knobs(set: Partial<Record<keyof AcidKnobs, number>> = {}): AcidKnobs {
  const one = (value: number) => new Float32Array([value]);
  return {
    cutoff: one(set.cutoff ?? 500),
    resonance: one(set.resonance ?? 0),
    envMod: one(set.envMod ?? 0),
    decay: one(set.decay ?? 0.5),
    accent: one(set.accent ?? 0),
    pitch: one(set.pitch ?? 0),
  };
}

const note = (frequency: number, more: Partial<AcidNote> = {}): AcidNote => ({
  frequency,
  accented: false,
  slide: false,
  ...more,
});

/** `seconds` of a synth struck with `first`, in blocks; `then` strikes more notes at their second. */
function render(
  set: Partial<Record<keyof AcidKnobs, number>>,
  first: AcidNote,
  seconds: number,
  then: { at: number; note: AcidNote }[] = [],
  shape: AcidShape = SAW,
) {
  const synth = new AcidSynth(shape, RATE);
  synth.strike(first);
  const out = new Float32Array(Math.round(seconds * RATE));
  const k = knobs(set);
  const due = [...then];
  let done = 0;
  while (done < out.length) {
    const next = due[0] ? Math.round(due[0].at * RATE) : Infinity;
    const to = Math.min(out.length, done + BLOCK, next);
    synth.render(out, done, to, k);
    done = to;
    if (done === next) synth.strike(due.shift()!.note);
  }
  return { out, synth };
}

/** How loud `hz` is in a stretch of the sound: the Goertzel magnitude through a Hann window, per sample. */
function energyAt(out: Float32Array, hz: number, from = 0, to = out.length): number {
  const w = (2 * Math.PI * hz) / RATE;
  const c = 2 * Math.cos(w);
  let s1 = 0;
  let s2 = 0;
  const n = to - from;
  for (let i = from; i < to; i++) {
    const hann = 0.5 - 0.5 * Math.cos((2 * Math.PI * (i - from)) / (n - 1));
    const s0 = out[i]! * hann + c * s1 - s2;
    s2 = s1;
    s1 = s0;
  }
  return Math.sqrt(s1 * s1 + s2 * s2 - c * s1 * s2) / (to - from);
}

const peak = (out: Float32Array, from = 0, to = out.length) => {
  let most = 0;
  for (let i = from; i < to; i++) most = Math.max(most, Math.abs(out[i]!));
  return most;
};

describe('the Acid synth (#421)', () => {
  it('plays a saw at the frequency of its note', () => {
    const { out } = render({ cutoff: 8000 }, note(110), 0.5);
    const at = energyAt(out, 110, 4800);
    expect(at).toBeGreaterThan(energyAt(out, 117, 4800) * 10);
    expect(energyAt(out, 220, 4800)).toBeGreaterThan(at * 0.2);
    expect(peak(out)).toBeLessThan(1);
  });

  it('takes the highs away below its cutoff', () => {
    const open = render({ cutoff: 6000 }, note(110), 0.3).out;
    const shut = render({ cutoff: 200 }, note(110), 0.3).out;
    const high = (out: Float32Array) => energyAt(out, 1100, 4800);
    expect(high(shut)).toBeLessThan(high(open) / 30);
  });

  it('rings at its cutoff the more, the higher the resonance', () => {
    // The 8th harmonic of 110 Hz sits right at the cutoff.
    const flat = render({ cutoff: 880, resonance: 0 }, note(110), 0.4).out;
    const ringing = render({ cutoff: 880, resonance: 0.9 }, note(110), 0.4).out;
    const ratio = (out: Float32Array) => energyAt(out, 880, 4800) / energyAt(out, 110, 4800);
    expect(ratio(ringing)).toBeGreaterThan(ratio(flat) * 4);
  });

  it('stays finite and in range at full resonance, sweep and accent', () => {
    const { out } = render(
      { cutoff: 12000, resonance: 1, envMod: 1, accent: 1, decay: 2 },
      note(55, { accented: true }),
      3,
      [0.5, 1, 1.5, 2].map((at, i) => ({ at, note: note(55 * 2 ** (i / 3), { accented: true }) })),
    );
    expect(out.every(Number.isFinite)).toBe(true);
    expect(peak(out)).toBeLessThan(1.5);
  });

  it('sweeps its filter open on every note and lets it fall in the decay', () => {
    const { out } = render({ cutoff: 200, envMod: 1, decay: 0.4 }, note(110), 0.6);
    const early = energyAt(out, 1100, 480, 2880);
    const late = energyAt(out, 1100, 21600, 24000);
    expect(early).toBeGreaterThan(late * 10);
  });

  it('makes an accented note louder and builds up on accents close behind each other', () => {
    const plain = render({ envMod: 0.5, accent: 1 }, note(110), 0.1).out;
    const accented = render({ envMod: 0.5, accent: 1 }, note(110, { accented: true }), 0.1).out;
    expect(peak(accented)).toBeGreaterThan(peak(plain) * 1.5);
    // A sixteenth at 120 BPM apart: the second accent starts with the first one's charge in it.
    const step = 0.125;
    const top = 0.04;
    const one = render({ accent: 1 }, note(110, { accented: true }), top).synth.state.charge;
    const two = render({ accent: 1 }, note(110, { accented: true }), step + top, [
      { at: step, note: note(110, { accented: true }) },
    ]).synth.state.charge;
    expect(two).toBeGreaterThan(one * 1.2);
  });

  it('glides to a note it slides to, without striking anew', () => {
    const shape = { wave: 'saw' as const, slideTime: 0.06 };
    const { synth } = render({}, note(110), 0.2, [{ at: 0.1, note: note(220, { slide: true }) }], shape);
    expect(synth.state.hz).toBeGreaterThan(215);
    const midway = render({}, note(110), 0.12, [{ at: 0.1, note: note(220, { slide: true }) }], shape);
    expect(midway.synth.state.hz).toBeGreaterThan(130);
    expect(midway.synth.state.hz).toBeLessThan(200);
    // The sweep runs on: it fell for 0.12 s and was not set back to the top.
    expect(midway.synth.state.sweep).toBeLessThan(0.5);
    const struck = render({}, note(110), 0.1005, [{ at: 0.1, note: note(220) }], shape);
    expect(struck.synth.state.hz).toBeCloseTo(220, 3);
    expect(struck.synth.state.sweep).toBeGreaterThan(0.9);
  });

  it('never slides on its first note', () => {
    const { synth } = render({}, note(220, { slide: true }), 0.01);
    expect(synth.state.hz).toBeCloseTo(220, 3);
    expect(synth.state.sweep).toBeGreaterThan(0.9);
  });

  it('draws a low-pass that loses 12 dB at its cutoff and peaks there with resonance', () => {
    expect(acidResponseDb(1000, 1000, 0)).toBeCloseTo(-12.04, 1);
    expect(acidResponseDb(50, 1000, 0)).toBeCloseTo(0, 1);
    expect(acidResponseDb(1000, 1000, 1)).toBeGreaterThan(acidResponseDb(50, 1000, 1) + 12);
    expect(acidResponseDb(8000, 1000, 0)).toBeLessThan(-60);
  });
});

describe('the line of an Acid (#421)', () => {
  /** Two notes on a line, the second sliding in at `slideAt`, played block by block in the order given. */
  function played(slideAt: number, blocks: number, order: 'first' | 'second') {
    const line = new AcidLine<'a' | 'b'>(new AcidSynth(SAW, RATE));
    line.strike('a', 0, note(110));
    line.strike('b', slideAt, note(165, { slide: true }));
    const a = new Float32Array(blocks * BLOCK);
    const b = new Float32Array(blocks * BLOCK);
    const k = knobs({ cutoff: 2000 });
    for (let n = 0; n < blocks; n++) {
      const frame = n * BLOCK;
      const into = (out: Float32Array) => out.subarray(frame, frame + BLOCK);
      if (order === 'first') {
        line.play('a', frame, into(a), k);
        line.play('b', frame, into(b), k);
      } else {
        line.play('b', frame, into(b), k);
        line.play('a', frame, into(a), k);
      }
    }
    return { a, b };
  }

  it('hands the synth to the note that slides in, from its first sample on', () => {
    const { a, b } = played(200, 4, 'first');
    expect(peak(a, 0, 200)).toBeGreaterThan(0.05);
    expect(peak(a, 200)).toBe(0);
    expect(peak(b, 0, 200)).toBe(0);
    expect(peak(b, 200)).toBeGreaterThan(0.05);
    // One synth: what both hear is what it plays with both notes struck in turn.
    const reference = render({ cutoff: 2000 }, note(110), (4 * BLOCK) / RATE, [
      { at: 200 / RATE, note: note(165, { slide: true }) },
    ]).out;
    const heard = a.map((value, i) => value + b[i]!);
    expect(Array.from(heard)).toEqual(Array.from(reference));
  });

  it('plays the same whichever note is run first in a block', () => {
    const one = played(300, 5, 'first');
    const two = played(300, 5, 'second');
    expect(Array.from(two.a)).toEqual(Array.from(one.a));
    expect(Array.from(two.b)).toEqual(Array.from(one.b));
  });

  it('is silent before its first note and says when its last one has gone', () => {
    const line = new AcidLine<'a'>(new AcidSynth(SAW, RATE));
    line.strike('a', 1000, note(110));
    const out = new Float32Array(BLOCK);
    line.play('a', 0, out, knobs());
    expect(peak(out)).toBe(0);
    expect(line.leave('a')).toBe(true);
  });
});

describe('the Acid node (#421)', () => {
  const graph = (params: PropertyBag = {}): Graph => ({
    nodes: [
      { id: 'notes', type: INSTRUMENT_NOTES, x: 0, y: 0, params: {} },
      { id: 'acid', type: INSTRUMENT_ACID, x: 200, y: 0, params },
      { id: 'out', type: INSTRUMENT_OUTPUT, x: 900, y: 0, params: {} },
    ],
    edges: [
      { id: 'e1', from: { node: 'notes', port: 'any' }, to: { node: 'acid', port: 'trigger' } },
      { id: 'e2', from: { node: 'acid', port: 'out' }, to: { node: 'out', port: 'in' } },
    ],
  });

  it('plays the note, tuned, with its knobs, and is accented by a hard velocity', () => {
    const sources = instrumentSourcesOf(makeProject().project);
    const build = compileInstrument(graph({ wave: 'square', tuning: 12, cutoff: 900 }), 60, sources);
    expect(build.reason).toBe('');
    const [layer] = build.layers;
    const soft = fxChainOf(layer!, { '@velocity': 0.8 });
    const hard = fxChainOf(layer!, { '@velocity': ACCENT_VELOCITY });
    if ('mix' in soft || 'mix' in hard) throw new Error('one way');
    expect(soft.acid).toMatchObject({
      id: 'acid',
      wave: 'square',
      cutoff: 900,
      resonance: 0.7,
      envMod: 0.5,
      decay: 0.5,
      accent: 0.6,
      slideTime: 0.06,
      accented: false,
    });
    expect(soft.acid!.frequency).toBeCloseTo(noteFrequency(72), 6);
    expect(hard.acid!.accented).toBe(true);
    expect(levelsOf(soft)).toEqual([900, 0.7, 0.5, 0.5, 0.6]);
  });

  it('holds its knobs to their rows', () => {
    const sources = instrumentSourcesOf(makeProject().project);
    const [layer] = compileInstrument(graph({ cutoff: 99999, resonance: 3, decay: 0 }), 60, sources).layers;
    const chain = fxChainOf(layer!, {});
    if ('mix' in chain) throw new Error('one way');
    expect(chain.acid).toMatchObject({ cutoff: 12000, resonance: 1, decay: 0.2 });
  });
});