Crystal/tests/audio.test.ts

import { describe, expect, it } from "vitest";
import { existsSync, readFileSync, writeFileSync } from "node:fs";
import { Apu, CPU_HZ, FRAME_CYCLES } from "../src/game/audio/apu";
import { AudioEngine } from "../src/game/audio/engine";
import { SOUND } from "../src/game/audio/constants";
import { RomReader } from "../src/game/rom/reader";
import { CrystalAssets } from "../src/game/rom/assets";
import { GameWorld } from "../src/game/world/world";

const RATE = 48000;
const romPath =
  process.env.CRYSTAL_ROM_PATH ??
  "Pokemon - Crystal Version (UE) (V1.1) [C][!].gbc";

function render(apu: Apu, seconds: number) {
  const count = Math.round(RATE * seconds);
  const left = new Float32Array(count),
    right = new Float32Array(count);
  apu.render(left, right, 0, count);
  return { left, right };
}
const rms = (samples: Float32Array, from = 0, to = samples.length) => {
  let sum = 0;
  for (let i = from; i < to; i++) sum += samples[i] * samples[i];
  return Math.sqrt(sum / Math.max(1, to - from));
};
/** Upward zero crossings per second. */
const pitch = (samples: Float32Array) => {
  let crossings = 0;
  for (let i = 1; i < samples.length; i++) if (samples[i - 1] < 0 && samples[i] >= 0) crossings++;
  return crossings / (samples.length / RATE);
};
const on = (apu: Apu) => {
  apu.write(0x16, 0x80); // NR52: power
  apu.write(0x14, 0x77); // NR50: full volume
  apu.write(0x15, 0xff); // NR51: every channel to both sides
};

describe("sound channels (apu.ts)", () => {
  it("plays a pulse note at 131072 / (2048 - frequency) Hz", () => {
    const apu = new Apu(RATE);
    on(apu);
    apu.write(0x01, 0x80); // 50% duty
    apu.write(0x02, 0xf0); // volume 15, no envelope
    apu.write(0x03, 1750 & 0xff);
    apu.write(0x04, 0x80 | (1750 >> 8));
    const { left } = render(apu, 1);
    expect(pitch(left)).toBeGreaterThan(436);
    expect(pitch(left)).toBeLessThan(444);
    expect(rms(left)).toBeGreaterThan(0.05);
  });
  it("fades a decreasing envelope out in 15 steps of 1/64 s", () => {
    const apu = new Apu(RATE);
    on(apu);
    apu.write(0x06, 0x80);
    apu.write(0x07, 0xf1); // volume 15, decrease every 1/64 s
    apu.write(0x08, 0x00);
    apu.write(0x09, 0x87);
    const { left } = render(apu, 0.5);
    expect(rms(left, 0, 2400)).toBeGreaterThan(0.05);
    // After 15/64 s the channel is silent but for the filter's settling.
    expect(rms(left, Math.round(RATE * 0.3))).toBeLessThan(0.01);
  });
  it("routes channels by NR51 and mutes the wave channel at level 0", () => {
    const apu = new Apu(RATE);
    on(apu);
    apu.write(0x15, 0x04); // wave channel to the right side only
    for (let i = 0; i < 16; i++) apu.write(0x20 + i, i < 8 ? 0xff : 0x00);
    apu.write(0x0a, 0x80);
    apu.write(0x0c, 0x20); // full level
    apu.write(0x0d, 0x00);
    apu.write(0x0e, 0x87);
    const { left, right } = render(apu, 0.25);
    expect(rms(left)).toBe(0);
    expect(rms(right)).toBeGreaterThan(0.05);
    apu.write(0x0c, 0x00);
    const quiet = render(apu, 0.25);
    expect(rms(quiet.right, 2400)).toBeLessThan(0.01);
  });
  it("plays noise without a steady pitch", () => {
    const apu = new Apu(RATE);
    on(apu);
    apu.write(0x11, 0xf0);
    apu.write(0x12, 0x32);
    apu.write(0x13, 0x80);
    const { left } = render(apu, 0.25);
    expect(rms(left)).toBeGreaterThan(0.05);
  });
  it("has 70224 cycles in a video frame of the 4 MiHz clock", () => {
    expect(CPU_HZ / FRAME_CYCLES).toBeCloseTo(59.7275, 3);
  });
});

describe.skipIf(!existsSync(romPath))("music from the local ROM", () => {
  const rom = () => new Uint8Array(readFileSync(romPath));
  it("renders Route 29's music through the engine and the channels", () => {
    const engine = new AudioEngine(new RomReader(rom()));
    const apu = new Apu(RATE);
    engine.initSound();
    engine.playMusic(SOUND.MUSIC_ROUTE_29);
    const seconds = 4;
    const samplesPerFrame = (RATE * FRAME_CYCLES) / CPU_HZ;
    const total = Math.round(RATE * seconds);
    const left = new Float32Array(total),
      right = new Float32Array(total);
    let done = 0,
      due = 0;
    while (done < total) {
      engine.updateSound();
      for (const write of engine.drain()) apu.write(write >> 8, write & 0xff);
      due += samplesPerFrame;
      const count = Math.min(total - done, Math.floor(due) - done);
      if (count > 0) apu.render(left, right, done, count);
      done += Math.max(0, count);
    }
    expect(rms(left)).toBeGreaterThan(0.03);
    expect(rms(right)).toBeGreaterThan(0.03);
    // A listening copy, for comparing with the original by ear.
    if (process.env.AUDIO_WAV) writeFileSync(process.env.AUDIO_WAV, wav(left, right));
  });
  it("plays each map's music on entry and fades between maps", () => {
    const world = new GameWorld(new CrystalAssets(rom()));
    world.restore({ ...world.save(), map: "24:3", x: 50, y: 10 });
    for (let tick = 0; tick < 4; tick++) world.tick();
    expect(world.sound.engine.mapMusic).toBe(SOUND.MUSIC_ROUTE_29);
    expect(world.sound.engine.channelMusicId(0)).toBe(SOUND.MUSIC_ROUTE_29);
    expect(world.mapMusicId()).toBe(SOUND.MUSIC_ROUTE_29);
  });
});

/** 16-bit stereo WAV. */
function wav(left: Float32Array, right: Float32Array) {
  const frames = left.length;
  const buffer = Buffer.alloc(44 + frames * 4);
  buffer.write("RIFF", 0);
  buffer.writeUInt32LE(36 + frames * 4, 4);
  buffer.write("WAVEfmt ", 8);
  buffer.writeUInt32LE(16, 16);
  buffer.writeUInt16LE(1, 20);
  buffer.writeUInt16LE(2, 22);
  buffer.writeUInt32LE(RATE, 24);
  buffer.writeUInt32LE(RATE * 4, 28);
  buffer.writeUInt16LE(4, 32);
  buffer.writeUInt16LE(16, 34);
  buffer.write("data", 36);
  buffer.writeUInt32LE(frames * 4, 40);
  for (let i = 0; i < frames; i++) {
    buffer.writeInt16LE(Math.max(-1, Math.min(1, left[i])) * 32767, 44 + i * 4);
    buffer.writeInt16LE(Math.max(-1, Math.min(1, right[i])) * 32767, 46 + i * 4);
  }
  return buffer;
}