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function waveToDataURL(wave){ | |
const f = n => '%' + (n >> 4).toString(16) + (n & 0xf).toString(16) | |
const f2 = n => f(n & 0xff) + f(n >> 8) | |
const f4 = n => f2(n & 0xffff) + f2(n >> 16) | |
return 'data:audio/wav,' + [ | |
'RIFF', | |
f4(wave.length * 2 + 32), | |
'WAVEfmt%20', | |
f4(16), | |
f4(0x10001), | |
f4(44100), | |
f4(88200), | |
f4(0x100004), | |
'data', | |
f4(wave.length * 2), | |
wave.map(v => { | |
v = Math.round(0x8000 * v); | |
return f2(v > 0x7fff ? 0x7fff : v < -0x7fff ? 0x8000 : v < 0 ? v + 0x10000 : v) | |
}).join('') | |
].join('') | |
} | |
audio=new Audio() | |
const waveData=new Array(44100 * 5).fill(0) | |
;[ | |
{ w: 2 / 24, hz: 441 * 1, fadein: 400, fadeout: 10000, delay: 0, volume: 1 }, | |
{ w: 4 / 24, hz: 441 * 1, fadein: 400, fadeout: 10000, delay: 0, volume: 1 }, | |
].forEach(({ w, hz, fadein, fadeout, delay, volume }) => { | |
const th = 2 * Math.PI * hz / 44100 | |
const ex = Math.exp(-w * hz / 44100 / 2) | |
const ac = ex * Math.cos(th) | |
const as = ex * Math.sin(th) | |
const bc = ex * ex * Math.cos(th) | |
const bs = ex * ex * Math.sin(th) | |
const scale = Math.sqrt(hz * w) * volume | |
let ar = 0, ai = 0 | |
let br = 0, bi = 0 | |
let sum2 = 0 | |
for(i = delay - 44100; i < waveData.length; i++) { | |
const r = 2 * Math.random() - 1 | |
let tmp | |
tmp = ar | |
ar = tmp * ac - ai * as + r | |
ai = ai * ac + tmp * as | |
tmp = br | |
br = tmp * bc - bi * bs + r | |
bi = bi * bc + tmp * bs | |
const j = i - delay | |
if (j < 0) continue | |
waveData[i] += (1 - Math.exp(-j / fadein)) * Math.exp(-j / fadeout) * (br - ar) * scale | |
} | |
console.log(w, hz, sum2) | |
}) | |
let max = 0; | |
waveData.forEach(v => { max = Math.max(max, Math.abs(v)) }) | |
waveData.forEach((_, i) => waveData[i] /= max) | |
console.log(max) | |
audio.src = waveToDataURL(waveData) | |
audio.play() |
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