feuerwerk/tests/core/parametric-eq.test.ts

/**
 * The Parametric EQ (#367): up to ten bands on one node, compiled to filters in a row, the curve the
 * editor draws from them, the curve in the node (#375), and the taps the spectrum is heard at (#374).
 */
import { describe, expect, it } from 'vitest';
import { CreateAssetCommand } from '../../src/core/commands/assetCommands';
import type { BehaviorAsset, SoundFxAsset } from '../../src/core/model/Asset';
import { compileSoundFx } from '../../src/core/soundfx/compile';
import { fxChainOf, SoundFxParametricEq, tapId } from '../../src/core/soundfx/nodes';
import {
  dbToY,
  type EqBand,
  eqBandResponse,
  eqBandsOf,
  eqCurves,
  fillShapes,
  frequencyToX,
  MAX_EQ_BANDS,
  withBandSet,
} from '../../src/core/soundfx/parametricEq';
import { SPECTRUM_FLOOR_DB, spectrumPeak, spectrumYs } from '../../src/editor/soundfx/eqView';
import { graphEditor, makeProject, roundTrip } from '../helpers';

const band = (change: Partial<EqBand>): EqBand => ({
  type: 'peaking',
  frequency: 1000,
  gain: 0,
  q: 1,
  slope: 12,
  ...change,
});

/** What one band does at a frequency, in dB, as the curves are worked out. */
const bandDb = (of: EqBand, frequency: number) => eqBandResponse(of)(frequency);

function eqLine(bands: unknown) {
  const f = makeProject();
  const command = new CreateAssetCommand('soundfx', 'EQ');
  f.stack.execute(command);
  const fx = command.asset as SoundFxAsset;
  const edit = graphEditor(f, fx as unknown as BehaviorAsset);
  const input = edit.addNode('SoundFxInput');
  const eq = edit.addNode('SoundFxParametricEq');
  eq.params.bands = bands as never;
  const output = edit.addNode('SoundFxOutput');
  edit.connect(input, 'out', eq, 'in');
  edit.connect(eq, 'out', output, 'in');
  return { ...f, fx, eq };
}

describe('the bands of a Parametric EQ', () => {
  it('are held to what the editor offers, at most ten of them', () => {
    const bands = eqBandsOf({
      bands: [
        { type: 'lowpass', frequency: 99999, gain: 3, q: 0, slope: 24 },
        { type: 'allpass', frequency: 5, gain: -99, q: 'x', slope: 7 },
        'not a band',
        ...Array.from({ length: 12 }, () => ({ type: 'peaking', frequency: 500 })),
      ],
    });
    expect(bands).toHaveLength(MAX_EQ_BANDS);
    expect(bands[0]).toEqual({ type: 'lowpass', frequency: 20000, gain: 3, q: 0.1, slope: 24 });
    expect(bands[1]).toEqual({ type: 'peaking', frequency: 20, gain: -24, q: Math.SQRT1_2, slope: 12 });
    expect(eqBandsOf({})).toEqual([]);
    expect(withBandSet([band({})], 0, { gain: 40 })[0]!.gain).toBe(24);
  });

  it('compile to one filter each, a steeper cut to more, and a flat peak to none', () => {
    const f = eqLine([
      band({ gain: 6 }),
      band({ type: 'highpass', frequency: 80, q: Math.SQRT1_2, slope: 24 }),
      band({ type: 'lowshelf', frequency: 200, gain: 0 }),
    ]);
    const build = compileSoundFx(f.fx.graph, undefined, f.fx.id);
    const id = tapId(f.fx.id, f.eq.id);
    expect(build.effects).toBe(1);
    expect(fxChainOf(build.compiled!).stages).toEqual([
      { kind: 'tap', id, at: 'in' },
      { kind: 'pass', filter: 'peaking', stages: 1, cutoff: 1000, q: 1, gain: 6 },
      { kind: 'pass', filter: 'highpass', stages: 2, cutoff: 80, q: 20 * Math.log10(Math.SQRT1_2), gain: 0 },
      { kind: 'tap', id, at: 'out' },
    ]);
    expect(roundTrip(f.project)).toEqual(f.project);
  });

  it('are tapped in front of the node and behind it, behind its Wet and when bypassed too', () => {
    const f = eqLine([band({ gain: 6 })]);
    const id = tapId(f.fx.id, f.eq.id);
    const kinds = () =>
      compileSoundFx(f.fx.graph, undefined, f.fx.id).compiled!.stages.map((s) =>
        s.kind === 'tap' ? `${s.at}:${s.id}` : s.kind,
      );
    f.eq.params.wet = 0.5;
    expect(kinds()).toEqual([`in:${id}`, 'wet', `out:${id}`]);
    f.eq.params.bypass = true;
    expect(kinds()).toEqual([`in:${id}`, `out:${id}`]);
  });

  it('draw the curve Web Audio plays', () => {
    const peak = band({ gain: 6 });
    expect(bandDb(peak, 1000)).toBeCloseTo(6, 3);
    expect(Math.abs(bandDb(peak, 20))).toBeLessThan(0.1);

    // A cut with no bump is 3 dB down at its frequency and falls 12 dB an octave below it.
    const cut = band({ type: 'highpass', frequency: 200, q: Math.SQRT1_2 });
    expect(bandDb(cut, 200)).toBeCloseTo(-3.01, 1);
    expect(bandDb(cut, 50) - bandDb(cut, 25)).toBeCloseTo(12, 0);
    const steeper = { ...cut, slope: 48 as const };
    expect(bandDb(steeper, 50) - bandDb(steeper, 25)).toBeCloseTo(48, 0);

    const shelf = band({ type: 'lowshelf', frequency: 200, gain: 6 });
    expect(bandDb(shelf, 20)).toBeCloseTo(6, 1);
    expect(bandDb(shelf, 200)).toBeCloseTo(3, 1);
    expect(bandDb(band({ type: 'notch' }), 1000)).toBeLessThan(-60);

    // Together they add up in dB; a band that does nothing is drawn but not counted.
    const flat = band({ type: 'peaking', frequency: 300, gain: 0 });
    const curves = eqCurves([peak, flat, shelf], [300, 3000]);
    expect(curves.bands[1]).toHaveLength(2);
    expect(curves.bands[2]![0]).toBeCloseTo(bandDb(shelf, 300), 6);
    expect(curves.sum[0]).toBeCloseTo(bandDb(peak, 300) + bandDb(shelf, 300), 6);
    expect(curves.sum[1]).toBeCloseTo(bandDb(peak, 3000) + bandDb(shelf, 3000), 6);
  });

  it('fills a curve that crosses 0 dB with one shape for each side, meeting on the line', () => {
    // From 10 above the line at y 50 to 10 below and back: it crosses twice, at x 15 and x 45.
    const shapes = fillShapes([0, 10, 20, 30, 40, 50, 60], [40, 40, 60, 60, 60, 40, 40], 50);
    expect(shapes).toEqual([
      [0, 50, 0, 40, 10, 40, 15, 50],
      [15, 50, 20, 60, 30, 60, 40, 60, 45, 50],
      [45, 50, 50, 40, 60, 40, 60, 50],
    ]);
    // On one side all along it stays one shape.
    expect(fillShapes([0, 10, 20], [40, 30, 40], 50)).toEqual([[0, 50, 0, 40, 10, 30, 20, 40, 20, 50]]);
  });
});

describe('the curve in the node (#375)', () => {
  const picture = SoundFxParametricEq.picture!;
  const W = 164;
  const area = { w: W, h: picture.height };
  const lineOf = (bands: unknown) => picture.shapes({ bands } as never, W).find((s) => s.kind === 'line')!;

  it('has its highest point where the peak is, as high as its gain', () => {
    const line = lineOf([band({ gain: 6 })]);
    let top = 1;
    for (let i = 3; i < line.points.length; i += 2) if (line.points[i]! < line.points[top]!) top = i;
    expect(Math.abs(line.points[top - 1]! - frequencyToX(1000, area))).toBeLessThanOrEqual(W / 96);
    expect(line.points[top]).toBeCloseTo(dbToY(6, area), 1);
    expect(line.points.length).toBe(97 * 2);
  });

  it('keeps its box without a band, flat on the 0 dB line', () => {
    const shapes = picture.shapes({}, W);
    const zero = dbToY(0, area);
    expect(picture.height).toBe(60);
    expect(shapes[0]).toEqual({ kind: 'guide', points: [0, zero, W, zero] });
    const line = shapes.find((s) => s.kind === 'line')!;
    expect(line.points.filter((_, i) => i % 2 === 1).every((y) => y === zero)).toBe(true);
  });

  it('stays inside its box however deep a cut goes', () => {
    const line = lineOf([band({ type: 'highpass', frequency: 2000, slope: 48 })]);
    const ys = line.points.filter((_, i) => i % 2 === 1);
    expect(Math.max(...ys)).toBe(picture.height);
    expect(Math.min(...ys)).toBeGreaterThanOrEqual(0);
  });
});

describe('the spectrum behind the curve (#374)', () => {
  const BIN = 48000 / 8192;
  const area = { w: 600, h: 300 };
  const xs = Array.from({ length: 301 }, (_, i) => i * 2);
  /** All silence but one loud bin at about 1 kHz. */
  const sine = () => {
    const dbs = new Float32Array(4096).fill(-Infinity);
    dbs[Math.round(1000 / BIN)] = -12;
    return dbs;
  };

  it('finds the loudest bin, and nothing in silence', () => {
    expect(spectrumPeak(sine(), BIN)!.hz).toBeCloseTo(Math.round(1000 / BIN) * BIN, 6);
    expect(spectrumPeak(sine(), BIN)!.db).toBe(-12);
    expect(spectrumPeak(new Float32Array(4096).fill(-Infinity), BIN)).toBeNull();
  });

  it('draws the loud bin where 1 kHz is, at its level, and silence on the floor', () => {
    const ys = spectrumYs(sine(), BIN, xs, area);
    const top = ys.indexOf(Math.min(...ys));
    expect(Math.abs(xs[top]! - frequencyToX(1000, area))).toBeLessThanOrEqual(2);
    expect(ys[top]).toBeCloseTo((-12 / SPECTRUM_FLOOR_DB) * area.h, 6);
    expect(ys.filter((y) => y === area.h).length).toBeGreaterThan(xs.length - 4);
  });

  it('down in the bass, where bins lie further apart than the points, goes between them', () => {
    const dbs = new Float32Array(4096).fill(-60);
    dbs[4] = -20;
    const at = (hz: number) => spectrumYs(dbs, BIN, [frequencyToX(hz, area)], area)[0]!;
    // Bin 4 is 23.4 Hz, bin 5 29.3 Hz: halfway the level is halfway.
    expect(at(4 * BIN)).toBeCloseTo((-20 / SPECTRUM_FLOOR_DB) * area.h, 6);
    expect(at(4.5 * BIN)).toBeCloseTo((-40 / SPECTRUM_FLOOR_DB) * area.h, 6);
  });
});