feuerwerk/tests/editor/compressor-view.test.ts

/**
 * What the tab of a Compressor draws (#378): its curve and the handles on it, the ratio a drag of
 * the end of the curve asks for, and the level picture tinted where the compressor works.
 */
import { describe, expect, it } from 'vitest';
import {
  type CompressorNumbers,
  compressorGainDb,
  curveDbAtX,
  curveDbAtY,
  curveOutDb,
  curveX,
  curveY,
  HISTORY_SECONDS,
  LevelHistory,
  levelY,
  ratioFor,
  ratioHandle,
  reductionOf,
  reductionShapes,
  thresholdHandle,
} from '../../src/editor/soundfx/compressorView';

const numbers: CompressorNumbers = {
  threshold: -24,
  knee: 0,
  ratio: 4,
  attack: 0.003,
  release: 0.25,
  makeup: 0,
  autoGain: 0,
};
const RATIO = { min: 1, max: 20, step: 0.1 };

describe('the curve of a Compressor', () => {
  it('leaves a level below the threshold as it is and squeezes one above it by the ratio', () => {
    expect(curveOutDb(-40, -24, 0, 4)).toBeCloseTo(-40, 6);
    // 24 dB over a threshold of -24 come out 6 dB over it at a ratio of 4.
    expect(curveOutDb(0, -24, 0, 4)).toBeCloseTo(-18, 1);
  });

  it('spans -60 to 0 dB on both axes, level out going up', () => {
    expect(curveX(-60, 300)).toBe(0);
    expect(curveX(0, 300)).toBe(300);
    expect(curveY(0, 300)).toBe(0);
    expect(curveDbAtX(150, 300)).toBe(-30);
    expect(curveDbAtY(100, 300)).toBe(-20);
  });

  it('has the threshold where it starts to bend and the ratio at its end', () => {
    expect(thresholdHandle(numbers, 300)).toEqual({ x: 180, y: 120 });
    const end = ratioHandle(numbers, 300);
    expect(end.x).toBe(300);
    expect(curveDbAtY(end.y, 300)).toBeCloseTo(-18, 1);
  });

  it('finds the ratio whose end is where it is dragged to, held to the range', () => {
    expect(ratioFor(-18, numbers, RATIO)).toBe(4);
    expect(ratioFor(-12, numbers, RATIO)).toBe(2);
    expect(ratioFor(5, numbers, RATIO)).toBe(1);
    expect(ratioFor(-40, numbers, RATIO)).toBe(20);
    // With a knee the curve ends lower than the straight line would, and the ratio found still lands there.
    const kneed = { ...numbers, knee: 6 };
    const ratio = ratioFor(-16, kneed, RATIO);
    expect(curveOutDb(0, -24, 6, ratio)).toBeCloseTo(-16, 0);
  });

  it('counts the makeup, the auto-gain or a blend of both as the gain after it', () => {
    expect(compressorGainDb({ ...numbers, makeup: 6 })).toBe(6);
    expect(compressorGainDb({ ...numbers, makeup: 6, autoGain: 1 })).toBeCloseTo(18, 1);
    expect(compressorGainDb({ ...numbers, makeup: 6, autoGain: 0.5 })).toBeCloseTo(12, 1);
  });
});

describe('the level picture of a Compressor', () => {
  it('spans +6 to -60 dB top to bottom, silence at the bottom', () => {
    expect(levelY(6, 660)).toBe(0);
    expect(levelY(-60, 660)).toBe(660);
    expect(levelY(-Infinity, 660)).toBe(660);
    expect(levelY(0, 660)).toBe(60);
  });

  it('keeps the readings of the last seconds and knows when all of them are silent', () => {
    const history = new LevelHistory();
    history.push(0, { in: -6, out: -9 });
    history.push(1, null);
    expect(history.heard).toBe(true);
    history.push(1 + HISTORY_SECONDS, null);
    expect(history.all.map((p) => p.t)).toEqual([1, 1 + HISTORY_SECONDS]);
    expect(history.heard).toBe(false);
  });

  it('takes away what came in less what went out, the gain after it left out', () => {
    expect(reductionOf({ in: -6, out: -12 }, 0)).toBe(6);
    expect(reductionOf({ in: -6, out: -6 }, 6)).toBe(6);
    expect(reductionOf({ in: -30, out: -29 }, 0)).toBe(0);
    expect(reductionOf({ in: -Infinity, out: -Infinity }, 0)).toBe(0);
  });

  it('tints from the level coming in down by what is taken away, one shape per stretch', () => {
    const points = [
      { t: 0, in: -6, out: -12 },
      { t: 1, in: -6, out: -12 },
      { t: 2, in: -30, out: -30 },
      { t: 3, in: 0, out: -3 },
      { t: 4, in: 0, out: -3 },
    ];
    const shapes = reductionShapes(points, 0, 4, 400, 660);
    expect(shapes).toHaveLength(2);
    // Along the level coming in, then back along it less what is taken away.
    expect(shapes[0]).toEqual([0, 120, 100, 120, 100, 180, 0, 180]);
    expect(shapes[1]).toEqual([300, 60, 400, 60, 400, 90, 300, 90]);
  });
});