feuerwerk/tests/core/pitch-player.test.ts

/**
 * The pitch of a sound FX in real time (#317): a sound played higher or lower keeps its length, also
 * while the pitch moves. Measured on a sine, whose pitch is the number of times it rises through zero
 * per second.
 */
import { describe, expect, it } from 'vitest';
import { PitchPlayer } from '../../src/core/soundfx/pitchPlayer';

const RATE = 48000;
const BLOCK = 128;
/** A frame at 48 kHz is 2048 samples, and a frame takes the pitch at the sample it starts on. */
const HALF_FRAME = 1024;

function sine(frequency: number, seconds: number, rate = RATE): Float32Array {
  const samples = new Float32Array(Math.round(rate * seconds));
  for (let i = 0; i < samples.length; i++) samples[i] = Math.sin((2 * Math.PI * frequency * i) / rate);
  return samples;
}

/** Plays the sound to its end block by block, as a worklet does, the pitch from `semitones(sample)`. */
function render(
  sound: Float32Array,
  semitones: number | ((at: number) => number),
  { step = 1, loop = false, blocks = Infinity } = {},
): Float32Array {
  const player = new PitchPlayer([sound], step, RATE, loop);
  const out: number[] = [];
  const block = new Float32Array(BLOCK);
  const pitch = new Float32Array(BLOCK);
  for (let b = 0; b < blocks; b++) {
    for (let i = 0; i < BLOCK; i++)
      pitch[i] = typeof semitones === 'number' ? semitones : semitones(out.length + i);
    const going = player.render([block], typeof semitones === 'number' ? [semitones] : pitch);
    out.push(...block);
    if (!going) break;
  }
  return Float32Array.from(out);
}

/** Rises through zero per second between two samples. */
function frequencyOf(
  samples: Float32Array,
  from = samples.length / 4,
  to = (samples.length * 3) / 4,
): number {
  let rises = 0;
  for (let i = Math.floor(from) + 1; i < to; i++) if (samples[i - 1]! < 0 && samples[i]! >= 0) rises++;
  return rises / ((to - from) / RATE);
}

const loudest = (samples: Float32Array) => samples.reduce((max, v) => Math.max(max, Math.abs(v)), 0);

/** The last sample that is not silence, plus one: how long the sound is heard. */
function heard(samples: Float32Array): number {
  let last = samples.length;
  while (last > 0 && Math.abs(samples[last - 1]!) <= 1e-4) last--;
  return last;
}

describe('the pitch player', () => {
  it.each([
    [12, 880],
    [-12, 220],
    [7, 440 * 2 ** (7 / 12)],
    [0.5, 440 * 2 ** (0.5 / 12)],
    [-30.5, 440 * 2 ** (-30.5 / 12)],
  ])('moves a 440 Hz tone by %d semitones to about %d Hz, at the same length', (semitones, expected) => {
    const tone = sine(440, 1);
    const shifted = render(tone, semitones);
    expect(shifted.length).toBeGreaterThanOrEqual(tone.length);
    expect(heard(shifted)).toBeLessThanOrEqual(tone.length);
    expect(heard(shifted)).toBeGreaterThan(tone.length - 50);
    expect(frequencyOf(shifted)).toBeGreaterThan(expected * 0.98);
    expect(frequencyOf(shifted)).toBeLessThan(expected * 1.02);
    expect(loudest(shifted)).toBeLessThan(1.2);
    expect(loudest(shifted.subarray(RATE / 4, (RATE * 3) / 4))).toBeGreaterThan(0.7);
  });

  it('plays a sound at 0 semitones as it is, from the very first sample', () => {
    const tone = sine(440, 0.5);
    const same = render(tone, 0);
    let off = 0;
    for (let i = 0; i < tone.length; i++) off = Math.max(off, Math.abs(same[i]! - tone[i]!));
    expect(off).toBeLessThan(1e-5);
    expect(heard(same)).toBe(tone.length);
  });

  it('starts the pitched sound at once rather than after a frame', () => {
    const shifted = render(sine(440, 0.5), 12);
    expect(loudest(shifted.subarray(0, 480))).toBeGreaterThan(0.3);
  });

  it('keeps the length while the pitch sweeps down, the pitch half a frame behind the sweep', () => {
    // A blip of a quarter second taken down two octaves over its own length.
    const tone = sine(880, 0.25);
    const sweep = (at: number) => (-24 * at) / tone.length;
    const swept = render(tone, sweep);
    expect(heard(swept)).toBeLessThanOrEqual(tone.length);
    expect(heard(swept)).toBeGreaterThan(tone.length - 50);
    for (const at of [tone.length / 4, (tone.length * 3) / 4]) {
      const expected = 880 * 2 ** (sweep(at - HALF_FRAME) / 12);
      const heardThere = frequencyOf(swept, at - 1200, at + 1200);
      expect(heardThere).toBeGreaterThan(expected * 0.95);
      expect(heardThere).toBeLessThan(expected * 1.05);
    }
  });

  it('reads a sound at its own rate: an 8 kHz tone comes out at its pitch and length', () => {
    const tone = sine(440, 0.5, 8000);
    const played = render(tone, 12, { step: 8000 / RATE });
    expect(heard(played)).toBeGreaterThan(RATE / 2 - 50);
    expect(heard(played)).toBeLessThanOrEqual(RATE / 2);
    expect(frequencyOf(played)).toBeGreaterThan(880 * 0.98);
    expect(frequencyOf(played)).toBeLessThan(880 * 1.02);
  });

  it('reads on across the end of a looping sound, so its seam does not fade out, and never ends', () => {
    const tone = sine(500, 0.25);
    const looped = render(tone, 12, { loop: true, blocks: Math.ceil((tone.length * 2) / BLOCK) });
    for (let from = tone.length - 960; from < tone.length + 960; from += 96)
      expect(loudest(looped.subarray(from, from + 96))).toBeGreaterThan(0.8);
    expect(heard(looped)).toBe(looped.length);
    expect(heard(render(tone, 12))).toBeLessThanOrEqual(tone.length);
  });

  it('goes from 0 semitones to a pitch and back without a dip, and then plays the sound as it is', () => {
    const tone = sine(440, 2);
    // Up to 5 over 0.1 s from a third in, back down over 0.1 s from two thirds.
    const ramp = (at: number) => Math.max(0, Math.min(1, (at - RATE / 3) / (RATE / 10)));
    const moved = render(tone, (at) => 5 * (ramp(at) - ramp(at - RATE / 3)));
    for (let from = 0; from + 480 <= tone.length; from += 480)
      expect(loudest(moved.subarray(from, from + 480))).toBeGreaterThan(0.8);
    const up = frequencyOf(moved, RATE * 0.5, RATE * 0.6);
    expect(up).toBeGreaterThan(440 * 2 ** (5 / 12) * 0.98);
    expect(up).toBeLessThan(440 * 2 ** (5 / 12) * 1.02);
    let off = 0;
    for (let i = RATE * 1.5; i < RATE * 2 - 50; i++) off = Math.max(off, Math.abs(moved[i]! - tone[i]!));
    expect(off).toBeLessThan(1e-5);
  });
});