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// MQ Synthesizer
// Replica oscillator bank for sinusoidal synthesis
// Evaluate cubic bezier curve at time t
function evalBezier(curve, t) {
const dt = curve.t3 - curve.t0;
if (dt <= 0) return curve.v0;
let u = (t - curve.t0) / dt;
u = Math.max(0, Math.min(1, u));
const u1 = 1.0 - u;
return u1*u1*u1 * curve.v0 +
3*u1*u1*u * curve.v1 +
3*u1*u*u * curve.v2 +
u*u*u * curve.v3;
}
// Deterministic LCG PRNG
function randFloat(seed, min, max) {
seed = (1664525 * seed + 1013904223) % 0x100000000;
return min + (seed / 0x100000000) * (max - min);
}
// Synthesize audio from MQ partials
// partials: array of {freqCurve, ampCurve, replicas?}
// replicas: {offsets, decay_alpha, jitter, spread_above, spread_below}
// integratePhase: true = accumulate 2π*f/SR per sample (correct for varying freq)
// false = 2π*f*t (simpler, only correct for constant freq)
function synthesizeMQ(partials, sampleRate, duration, integratePhase = true) {
const numSamples = Math.floor(sampleRate * duration);
const pcm = new Float32Array(numSamples);
const defaultReplicas = {
offsets: [1.0],
decay_alpha: 0.1,
jitter: 0.05,
spread_above: 0.02,
spread_below: 0.02
};
// Pre-build per-partial configs with fixed spread/jitter and phase accumulators
const configs = [];
for (let p = 0; p < partials.length; ++p) {
const rep = partials[p].replicas != null ? partials[p].replicas : defaultReplicas;
const offsets = rep.offsets != null ? rep.offsets : [1.0];
const decay_alpha = rep.decay_alpha != null ? rep.decay_alpha : 0.0;
const jitter = rep.jitter != null ? rep.jitter : 0.0;
const spread_above = rep.spread_above != null ? rep.spread_above : 0.0;
const spread_below = rep.spread_below != null ? rep.spread_below : 0.0;
const replicaData = [];
for (let r = 0; r < offsets.length; ++r) {
// Fixed per-replica spread (frequency detuning) and initial phase (jitter)
const spread = randFloat(p * 67890 + r * 999, -spread_below, spread_above);
const initPhase = randFloat(p * 67890 + r, 0.0, 1.0) * jitter * 2.0 * Math.PI;
replicaData.push({ratio: offsets[r], spread, phase: initPhase});
}
configs.push({
fc: partials[p].freqCurve,
ac: partials[p].ampCurve,
decay_alpha,
replicaData
});
}
for (let i = 0; i < numSamples; ++i) {
const t = i / sampleRate;
let sample = 0.0;
for (let p = 0; p < configs.length; ++p) {
const {fc, ac, decay_alpha, replicaData} = configs[p];
if (t < fc.t0 || t > fc.t3) continue;
const f0 = evalBezier(fc, t);
const A0 = evalBezier(ac, t);
for (let r = 0; r < replicaData.length; ++r) {
const rep = replicaData[r];
const f = f0 * rep.ratio * (1.0 + rep.spread);
const A = A0 * Math.exp(-decay_alpha * Math.abs(f - f0));
let phase;
if (integratePhase) {
rep.phase += 2.0 * Math.PI * f / sampleRate;
phase = rep.phase;
} else {
phase = 2.0 * Math.PI * f * t + rep.phase;
}
sample += A * Math.sin(phase);
}
}
pcm[i] = sample;
}
// Normalize
let maxAbs = 0;
for (let i = 0; i < numSamples; ++i) maxAbs = Math.max(maxAbs, Math.abs(pcm[i]));
if (maxAbs > 1.0) {
for (let i = 0; i < numSamples; ++i) pcm[i] /= maxAbs;
}
return pcm;
}
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