home-server/services/observer-effect/site/sound.js

/* Optional soundscape for the player screen — the "flutes and drums" the
   scenario keeps describing. Silent until the player clicks to enable it
   (browsers block audio without a gesture). All synthesized; no asset files. */
(function () {
  "use strict";

  let ctx = null;
  let master = null;
  let droneGain = null;

  // Pre-rendered ffmpeg SFX (see sfx/generate.sh). Decoded into buffers on
  // enable; if a file fails to load we fall back to the synth below.
  const FILES = {
    pulse: "sfx/pulse.mp3",
    communion: "sfx/communion.mp3",
    whisper: "sfx/whisper.mp3",
    relay: "sfx/relay.wav",
  };
  const buffers = {};

  function loadBuffers() {
    for (const [name, url] of Object.entries(FILES)) {
      fetch(new URL(url, location.href))
        .then((r) => (r.ok ? r.arrayBuffer() : Promise.reject()))
        .then((data) => ctx.decodeAudioData(data))
        .then((buf) => (buffers[name] = buf))
        .catch(() => {});
    }
  }

  function play(name) {
    const buf = buffers[name];
    if (!buf || !ctx) return false;
    const src = ctx.createBufferSource();
    src.buffer = buf;
    src.connect(master);
    src.start();
    return true;
  }

  function enable() {
    if (ctx) return true;
    const AC = window.AudioContext || window.webkitAudioContext;
    if (!AC) return false;
    ctx = new AC();
    master = ctx.createGain();
    master.gain.value = 0.8;
    master.connect(ctx.destination);

    // A near-subaudible drone that swells as communion nears (see setDread).
    droneGain = ctx.createGain();
    droneGain.gain.value = 0;
    droneGain.connect(master);
    const drone = ctx.createOscillator();
    drone.type = "sine";
    drone.frequency.value = 33;
    const drone2 = ctx.createOscillator();
    drone2.type = "sine";
    drone2.frequency.value = 33.4; // beat against the first for unease
    drone.connect(droneGain);
    drone2.connect(droneGain);
    drone.start();
    drone2.start();

    // Mains hum: this is a high-voltage 1964 nixie device, so it's never truly
    // silent. A 60 Hz transformer hum with harmonics plus a faint HV whine,
    // synthesized live so it loops seamlessly. Constant while sound is on.
    const humGain = ctx.createGain();
    humGain.gain.value = 0.07;
    humGain.connect(master);
    const humLfo = ctx.createOscillator(); // slow amplitude waver
    humLfo.frequency.value = 0.5;
    const humLfoGain = ctx.createGain();
    humLfoGain.gain.value = 0.012;
    humLfo.connect(humLfoGain).connect(humGain.gain);
    humLfo.start();
    const humLp = ctx.createBiquadFilter();
    humLp.type = "lowpass";
    humLp.frequency.value = 500;
    humLp.connect(humGain);
    [[60, 0.5], [120, 0.32], [180, 0.12]].forEach(([f, g]) => {
      const o = ctx.createOscillator();
      o.type = "sine";
      o.frequency.value = f;
      const og = ctx.createGain();
      og.gain.value = g;
      o.connect(og).connect(humLp);
      o.start();
    });
    const whine = ctx.createOscillator(); // high-voltage supply whine
    whine.type = "sine";
    whine.frequency.value = 15000;
    const whineGain = ctx.createGain();
    whineGain.gain.value = 0.015;
    whine.connect(whineGain).connect(humGain);
    whine.start();

    loadBuffers();
    return true;
  }

  function enabled() {
    return !!ctx;
  }

  // Low drum thump + a thin flute whistle: one "pulse" of Azathoth's court.
  function synthPulse() {
    if (!ctx) return;
    const t = ctx.currentTime;

    const drum = ctx.createOscillator();
    const dg = ctx.createGain();
    drum.type = "sine";
    drum.frequency.setValueAtTime(64, t);
    drum.frequency.exponentialRampToValueAtTime(34, t + 0.5);
    dg.gain.setValueAtTime(0.0001, t);
    dg.gain.exponentialRampToValueAtTime(0.9, t + 0.02);
    dg.gain.exponentialRampToValueAtTime(0.0001, t + 0.7);
    drum.connect(dg).connect(master);
    drum.start(t);
    drum.stop(t + 0.75);

    const flute = ctx.createOscillator();
    const fg = ctx.createGain();
    flute.type = "triangle";
    flute.frequency.setValueAtTime(1900, t);
    flute.frequency.exponentialRampToValueAtTime(3300, t + 0.6);
    fg.gain.setValueAtTime(0.0001, t);
    fg.gain.exponentialRampToValueAtTime(0.12, t + 0.05);
    fg.gain.exponentialRampToValueAtTime(0.0001, t + 0.65);
    flute.connect(fg).connect(master);
    flute.start(t);
    flute.stop(t + 0.7);
  }

  function noise(dur) {
    const len = Math.floor(ctx.sampleRate * dur);
    const buf = ctx.createBuffer(1, len, ctx.sampleRate);
    const data = buf.getChannelData(0);
    for (let i = 0; i < len; i++) data[i] = Math.random() * 2 - 1;
    return buf;
  }

  // The full extrusion: a rising roar and noise swell that detonate into a
  // sub-bass impact, then a cluster of screaming flutes over a void drone.
  // Timed so the impact lands with the visual blast (~1.6s in).
  function synthCommunion() {
    if (!ctx) return;
    const t = ctx.currentTime;
    const blast = t + 1.6;

    // rising roar into the blast
    const roar = ctx.createOscillator();
    const rg = ctx.createGain();
    roar.type = "sawtooth";
    roar.frequency.setValueAtTime(26, t);
    roar.frequency.exponentialRampToValueAtTime(64, blast);
    roar.frequency.exponentialRampToValueAtTime(30, blast + 2.6);
    rg.gain.setValueAtTime(0.0001, t);
    rg.gain.exponentialRampToValueAtTime(0.5, blast);
    rg.gain.exponentialRampToValueAtTime(0.0001, blast + 3.2);
    roar.connect(rg).connect(master);
    roar.start(t);
    roar.stop(blast + 3.4);

    // reverse-cymbal noise swell sucking up into the blast
    const sw = ctx.createBufferSource();
    sw.buffer = noise(2);
    const swf = ctx.createBiquadFilter();
    swf.type = "highpass";
    swf.frequency.setValueAtTime(200, t);
    swf.frequency.exponentialRampToValueAtTime(9000, blast);
    const swg = ctx.createGain();
    swg.gain.setValueAtTime(0.0001, t);
    swg.gain.exponentialRampToValueAtTime(0.22, blast);
    swg.gain.exponentialRampToValueAtTime(0.0001, blast + 0.4);
    sw.connect(swf).connect(swg).connect(master);
    sw.start(t);
    sw.stop(blast + 0.5);

    // THE IMPACT: a plunging sub-bass body + a broadband burst
    const imp = ctx.createOscillator();
    const ig = ctx.createGain();
    imp.type = "sine";
    imp.frequency.setValueAtTime(82, blast);
    imp.frequency.exponentialRampToValueAtTime(18, blast + 0.8);
    ig.gain.setValueAtTime(0.0001, blast);
    ig.gain.exponentialRampToValueAtTime(0.95, blast + 0.03);
    ig.gain.exponentialRampToValueAtTime(0.0001, blast + 1.4);
    imp.connect(ig).connect(master);
    imp.start(blast);
    imp.stop(blast + 1.5);

    const burst = ctx.createBufferSource();
    burst.buffer = noise(1);
    const bf = ctx.createBiquadFilter();
    bf.type = "bandpass";
    bf.frequency.value = 1100;
    bf.Q.value = 0.4;
    const bg = ctx.createGain();
    bg.gain.setValueAtTime(0.55, blast);
    bg.gain.exponentialRampToValueAtTime(0.0001, blast + 0.6);
    burst.connect(bf).connect(bg).connect(master);
    burst.start(blast);
    burst.stop(blast + 0.7);

    // screaming flute cluster after the rupture
    [1700, 2050, 2390, 2900, 3550, 4200].forEach((f, i) => {
      const o = ctx.createOscillator();
      const g = ctx.createGain();
      o.type = "triangle";
      o.frequency.setValueAtTime(f, blast);
      o.frequency.linearRampToValueAtTime(f * 1.22, blast + 2.6);
      g.gain.setValueAtTime(0.0001, blast + i * 0.06);
      g.gain.exponentialRampToValueAtTime(0.06, blast + 0.3 + i * 0.06);
      g.gain.exponentialRampToValueAtTime(0.0001, blast + 3);
      o.connect(g).connect(master);
      o.start(blast + i * 0.06);
      o.stop(blast + 3.2);
    });

    // void drone tail (two detuned sines, beating)
    const vg = ctx.createGain();
    vg.gain.setValueAtTime(0.0001, blast + 0.2);
    vg.gain.exponentialRampToValueAtTime(0.3, blast + 1);
    vg.gain.exponentialRampToValueAtTime(0.0001, blast + 4);
    vg.connect(master);
    [40, 40.5].forEach((f) => {
      const o = ctx.createOscillator();
      o.type = "sine";
      o.frequency.value = f;
      o.connect(vg);
      o.start(blast);
      o.stop(blast + 4.2);
    });
  }

  // level 0..1 — swells the drone with tension, but cuts cleanly to silence
  // once tension is spent so the deep pulse doesn't hang around.
  function setDread(level) {
    if (!ctx || !droneGain) return;
    const clamped = Math.max(0, Math.min(1, level));
    const now = ctx.currentTime;
    if (clamped <= 0.08) {
      droneGain.gain.cancelScheduledValues(now);
      droneGain.gain.setTargetAtTime(0, now, 0.3);
      return;
    }
    droneGain.gain.setTargetAtTime(clamped * 0.22, now, 1.5);
  }

  // File first, synth as fallback.
  function pulse() {
    if (!play("pulse")) synthPulse();
  }
  function communion() {
    if (!play("communion")) synthCommunion();
  }
  function message() {
    play("whisper");
  }

  // Per-second stepping relay — consistent level, no variation. Optionally
  // scheduled at a future AudioContext time (`when`) so ticks keep firing while
  // the tab is backgrounded. Pending clicks are tracked so they can be canceled.
  let pendingTicks = [];
  function step(when) {
    if (!ctx) return;
    const at = when || ctx.currentTime;
    const g = ctx.createGain();
    g.gain.value = 0.4;
    g.connect(master);
    let node;
    if (buffers.relay) {
      node = ctx.createBufferSource();
      node.buffer = buffers.relay;
      node.connect(g);
      node.start(at);
    } else {
      node = ctx.createOscillator();
      node.type = "square";
      node.frequency.value = 1800;
      const e = ctx.createGain();
      e.gain.setValueAtTime(0.0001, at);
      e.gain.exponentialRampToValueAtTime(0.4, at + 0.002);
      e.gain.exponentialRampToValueAtTime(0.0001, at + 0.03);
      node.connect(e).connect(g);
      node.start(at);
      node.stop(at + 0.04);
    }
    pendingTicks.push({ node, at });
    if (pendingTicks.length > 64) {
      pendingTicks = pendingTicks.filter((p) => p.at > ctx.currentTime - 1);
    }
  }

  // Stop any clicks scheduled for the future (e.g. on pause or a clock jump).
  function cancelTicks() {
    if (!ctx) return;
    const t = ctx.currentTime;
    for (const p of pendingTicks) {
      if (p.at > t) {
        try {
          p.node.stop(t);
        } catch (_) {}
      }
    }
    pendingTicks = pendingTicks.filter((p) => p.at > t);
  }

  function audioNow() {
    return ctx ? ctx.currentTime : 0;
  }

  window.OESound = {
    enable,
    enabled,
    pulse,
    communion,
    message,
    step,
    cancelTicks,
    now: audioNow,
    setDread,
  };
})();