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renderer.js
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renderer.js
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importScripts(
"lib/bezier-easing.js",
"lib/fft.js",
"lib/mersenne-twister.js",
"delay.js",
"envelope.js",
"resampler.js",
)
function normalize(wave) {
var max = 0.0
for (var t = 0; t < wave.length; ++t) {
var value = Math.abs(wave[t])
if (max < value) {
max = value
}
}
if (max === 0.0) {
console.log("renderer.js normalize(): max === 0.")
return wave
}
var amp = 1.0 / max
for (var t = 0; t < wave.length; ++t) {
wave[t] *= amp
}
return wave
}
// Karplus-Strong string synthesis.
class KSString {
constructor(sampleRate, frequency, filterBias) {
this.delay = new Delay(sampleRate, 1.0 / frequency)
this.lowpass = new OneZeroLP(filterBias)
this.highpass = new RCHP(0.5)
this.feedback = 0
}
process(input) {
var output = this.delay.process(input + this.feedback)
this.feedback = this.lowpass.process(output)
return this.highpass.process(output)
}
}
class OneZeroLP {
// One-Zero filter
// https://ccrma.stanford.edu/~jos/filters/One_Zero.html
//
// b1 = [-1, 1]
constructor(b1) {
this.z1 = 0
this.b1 = b1
}
process(input) {
// var output = this.b1 * (this.z1 - input) + input
var output = this.b1 * (input - this.z1) + this.z1
this.z1 = input
return output
}
}
class AverageFilter {
constructor(bufferSize) {
this.buffer = new Array(bufferSize).fill(0)
this.sum = 0.0
this.denom = bufferSize + 1
}
process(input) {
var output = (this.sum + input) / this.denom
this.buffer.unshift(input)
this.sum += input - this.buffer.pop()
return output
}
}
class RCHP {
// https://en.wikipedia.org/wiki/High-pass_filter
// alpha is smoothing factor.
constructor(alpha) {
this.alpha = alpha
this.y = 0
this.z1 = 0
}
process(input) {
this.y = this.alpha * this.y + this.alpha * (input - this.z1)
this.z1 = input
return this.y
}
}
function toFrequency(semitone) {
return 440.0 * Math.pow(2.0, semitone / 12.0)
}
function render(params, tone, sampleRate, waveLength, rnd) {
var wave = new Array(waveLength).fill(0)
var frequency = toFrequency(params.transpose + params.chord[tone])
// Render excitation.
var preFilter = []
for (var i = 0; i < 8; ++i) {
preFilter.push(new Comb(
sampleRate,
params.pickCombTime / frequency * rnd.random(),
-1,
params.pickCombFB
))
}
var period = Math.floor(sampleRate / frequency) * params.pickTime
var delay = Math.floor(
tone * params.delayTime * (params.jitter * rnd.random() + 1) * sampleRate)
var attackLength = period / 2
var attackTime = delay + attackLength
var endPick = delay + period
endPick = (endPick < wave.length) ? endPick : wave.length
for (var i = delay; i < endPick; ++i) {
wave[i] = rnd.random() - 0.5
}
for (var i = delay; i < wave.length; ++i) {
var sig = wave[i]
if (i < attackTime) {
sig *= (1 - Math.cos((i - delay) * Math.PI / attackLength)) / 2
}
for (f of preFilter) {
sig = f.process(sig)
}
wave[i] = sig
}
// Render string.
var string = []
for (var i = 0; i < params.stack; ++i) {
string.push(new KSString(
sampleRate,
frequency * Math.pow(params.stackDetune, i),
0.5
))
}
var phase = new Array(string.length)
for (var i = 0; i < phase.length; ++i) {
phase[i] = (params.stackDetune < 1.1)
? Math.floor(period * rnd.random())
: Math.floor(rnd.random()) // 乱数を消費。
}
var waveLastIndex = wave.length - 1
for (var i = 0; i < wave.length; ++i) {
var sig = 0
for (var j = 0; j < string.length; ++j) {
var index = Math.min(i + phase[j], waveLastIndex)
sig += string[j].process(wave[index])
}
wave[i] += sig
}
if (params.cutoff < 1.0) {
var lowpass = new SVFStack(sampleRate, 4)
lowpass.cutoff = params.cutoff
+ params.cutoffVariation * (1.0 - params.cutoff) * rnd.random()
lowpass.q = params.qVariation * rnd.random()
for (var i = 0; i < wave.length; ++i) {
wave[i] = lowpass.lowpass(wave[i])
}
}
return wave
}
// params = {
// length,
// sampleRate,
// overSampling,
// transpose,
// seed,
// chord,
// delayTime,
// jitter,
// stack,
// stackDetune,
// cutoff,
// cutoffVariation,
// qVariation,
// pickTime,
// pickCombFB,
// pickCombTime,
// }
onmessage = (event) => {
var params = event.data
// console.log(params)
var sampleRate = params.sampleRate * params.overSampling
var waveLength = Math.floor(sampleRate * params.length)
var wave = new Array(waveLength).fill(0)
var rnd = new MersenneTwister(params.seed)
for (var tone = 0; tone < params.chord.length; ++tone) {
var waveTemp = render(params, tone, sampleRate, waveLength, rnd)
for (var i = 0; i < wave.length; ++i) {
wave[i] += waveTemp[i]
}
}
// down sampling.
if (params.overSampling > 1) {
wave = Resampler.pass(wave, sampleRate, params.sampleRate)
}
postMessage(wave)
}