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e_EQ.js
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e_EQ.js
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Playfield.register_experiment('EQ', function(_module) {
const tau = 2*Math.PI;
/** @typedef {number} FilterType */
const NODE_LPF = 0;
const NODE_HPF = 1;
/** @typedef {{ type: FilterType, cutoff: number, order: number, color?: Color, color_dim?: Color, color_light?: Color }} ParametricNode */
/** @type {Plotter} */
let plot;
/** @type {{ samres: number, nodes: ParametricNode[], legend: Legend }} */
let ctx;
function Color(r, g, b) {
if (new.target == null)
throw new Error('Color is a constructor');
this.r = r;
this.g = g;
this.b = b;
}
Color.Random = function RandomColor() {
return new Color(
Math.floor(Math.random()*255),
Math.floor(Math.random()*255),
Math.floor(Math.random()*255));
};
Color.prototype.Dim = function DimColor() {
let r = this.r;
let g = this.g;
let b = this.b;
r = Math.floor(r*0.8);
g = Math.floor(g*0.6);
b = Math.floor(b*0.8);
return new Color(r, g, b);
};
Color.prototype.Lighten = function DimColor() {
let r = this.r;
let g = this.g;
let b = this.b;
r = Math.min(Math.floor(r*1.2), 0xFF);
g = Math.min(Math.floor(g*1.5), 0xFF);
b = Math.min(Math.floor(b*1.2), 0xFF);
return new Color(r, g, b);
};
Color.prototype.toString = function() {
const r = this.r.toString(16).padStart(2, '0');
const g = this.g.toString(16).padStart(2, '0');
const b = this.b.toString(16).padStart(2, '0');
return `#${r}${g}${b}`;
};
// Complex Float32Buffer subarray wrapper
function CSubarray(buf, start, stride, size) {
this.buf = buf;
this.start = start;
this.stride = stride;
this.size = size;
}
CSubarray.prototype.get = function(i) {
return _cmp_buf(this.buf, this.start + i*this.stride);
};
CSubarray.prototype.set = function(i, v) {
this.buf[2*(this.start + i*this.stride)+0] = v.re;
this.buf[2*(this.start + i*this.stride)+1] = v.im;
};
CSubarray.prototype.sub = function(offset, stride, size) {
return new CSubarray(this.buf, this.start + offset*this.stride, this.stride*stride, size);
};
/** @summary One chunk of FFT: computes FFT of a subarray; Implements Cooley-Turkey algorithm.
* @param {CSubarray} buf Given source buffer
* @param {CSubarray} out Output buffer
*/
function FFT(buf, out) {
if (buf.size !== out.size)
throw new Error("Somethin's gon' wrong >:[");
const N = out.size;
if (N === 1) {
// out[0] := buf[0]
out.set(0, buf.get(0));
} else {
const n = N/2;
FFT(buf.sub(0, 2, n), out.sub(0, 1, n));
FFT(buf.sub(1, 2, n), out.sub(n, 1, n));
for (let k = 0; k < n; k++) {
// t := out[idx + k*s]
let t = out.get(k);
// c := expi(-tau k/N) * out[idx + (k+n)*s]
let c = _cmp_mul(_exp_i(-tau*k/N), out.get(k+n));
// out[idx + k*s] := t + exp(-i tau*k/N) * out[idx + (k+n)*s] = t + c;
out.set(k, _cmp_add(t, c));
// out[idx + (k+n)*s] := t - exp(-i tau*k/N) * out[idx + (k+n)*s] = t - c;
out.set(k+n, _cmp_sub(t, c));
}
}
}
/** @summary Computes FFT of a given chunk
* @param {Float32Array} buf Target buffer
* @param {number} offset Offset of the buffer (in samples)
* @param {number} size Number of samples to processs
* @returns {Float32Array} The FFT of `buf`
*/
function PerformFFT(buf, offset, size) {
// Is size a power of 2?
if (((size - 1) & size) !== 0)
throw new RangeError('Size must be a power of 2!');
let out = new Float32Array(2*size);
FFT(new CSubarray(buf.subarray(2*offset), 0, 1, size), new CSubarray(out, 0, 1, size));
// Scale the output
let s = 1 / Math.sqrt(size);
for (let i = 0; i < 2*size; i++) {
out[i] *= s;
}
return out;
}
function ConvertComplex2Polar(buf) {
const l = Math.floor(buf.length/2);
let out = new Float32Array(2*l);
for (let n = 0; n < l; n++) {
let r = buf[2*n+0], i = buf[2*n+1];
let mag = out[2*n+0] = Math.sqrt(r*r + i*i);
if (mag < Number.EPSILON)
out[2*n+1] = 0;
else
out[2*n+1] = Math.atan2(i, r);
}
return out;
}
function sinc(x) {
return x === 0 ? 1 : Math.sin(x) / x;
}
/*
F{LPF} ~= rect(s, cutoff)
F{HPF} ~= s - rect(s, cutoff) = s - F{LPF}
T{HPF} = l*ð - T{LPF}
*/
function ComputeFilter(node) {
if (node.type !== NODE_LPF && node.type !== NODE_HPF)
throw new Error('Unknown filter type');
const buffer = new Float32Array(2*ctx.samres);
// Use rectangular window
switch (node.type) {
case NODE_LPF:
buffer[0] = node.cutoff / ctx.samres;
for (let i = 1; i < node.order; ++i) {
buffer[2*(ctx.samres - i)] =
buffer[2*i] = Math.sin(i*Math.PI*node.cutoff/ctx.samres) / (i*Math.PI);
}
break;
case NODE_HPF:
buffer[0] = 1-node.cutoff / ctx.samres;
for (let i = 1; i < node.order; ++i) {
buffer[2*(ctx.samres - i)] =
buffer[2*i] = -Math.sin(i*Math.PI*node.cutoff/ctx.samres) / (i*Math.PI);
}
break;
}
/*for (let i = node.order; i <= ctx.samres - node.order; ++i)
buffer[2*i] = 1;*/
return buffer;
}
function ConvolveFilters(nodes) {
/** @todo */
}
function ComputeFunctions() {
ctx.impres = ComputeFilter(ctx.nodes[0]);
ctx.impres_polar = ConvertComplex2Polar(ctx.impres);
ctx.trans = PerformFFT(ctx.impres, 0, ctx.samres);
ctx.trans_polar = ConvertComplex2Polar(ctx.trans);
let peak = 0;
for (let idx = 0; idx < ctx.samres/2; ++idx) {
const sam = ctx.trans_polar[2*idx];
if (sam > peak)
peak = sam;
}
ctx.trans_peak = peak;
//console.log(ctx.trans_polar);
}
_module.init = function init() {
plot = new Plotter(_module.canvas);
ctx = {
samres: 1024, // Sample resolution
nodes: [],
legend: plot.CreateLegend(),
mouse: { target: null, dragging: false },
};
ctx.nodes.push({
type: NODE_LPF,
cutoff: 700,
order: 200,
});
ctx.color = plot.RegisterLegendLabel(ctx.legend, 'Transform function', '#02E028');
ctx.impcolor = plot.RegisterLegendLabel(ctx.legend, 'Impulse response', '#10D0FF');
ctx.phcolor = plot.RegisterLegendLabel(ctx.legend, 'Transform phase shift', '#D050C0');
ComputeFunctions();
Playfield.register_handler(_module, 'mousedown', ev => {
if (Math.abs(ev.offsetY - _module.canvas.height + 80) < 20) {
ev.preventDefault();
let idx = Math.floor((ev.offsetX - 5) / 40);
if (idx >= 0 && idx < ctx.nodes.length) {
ctx.nodes[idx].type = 1 - ctx.nodes[idx].type;
ComputeFunctions();
}
return;
}
if (ctx.mouse.target === null)
return;
ctx.mouse.dragging = true;
});
Playfield.register_handler(_module, 'mousemove', ev => {
const cutoff = ev.offsetX / _module.canvas.width * ctx.samres;
if (ctx.mouse.dragging) {
if (ctx.mouse.target)
ctx.mouse.target.cutoff = cutoff;
} else {
let target = null;
if (Math.abs(ev.offsetY - _module.canvas.height * 0.35) <= 15) {
for (let handle of ctx.nodes) {
if (Math.abs(handle.cutoff - cutoff) > 50)
continue;
if (target === null || Math.abs(handle.cutoff - cutoff) < Math.abs(target.cutoff - cutoff))
target = handle;
}
}
ctx.mouse.target = target;
}
});
Playfield.register_handler(_module, 'mouseup', ev => {
if (!ctx.mouse.dragging)
return;
ctx.mouse.dragging = false;
ComputeFunctions();
});
};
_module.render = function render() {
const {cnv, ctx: dctx} = plot;
dctx.clearRect(0, 0, cnv.width, cnv.height);
dctx.strokeStyle = '#000000';
dctx.beginPath();
dctx.moveTo(0, cnv.height/2);
dctx.lineTo(cnv.width, cnv.height/2);
dctx.stroke();
//plot.PlotBuffer(ctx.trans, {scale: 10*Math.sqrt(ctx.samres), color: ctx.legend.colors[ctx.color], start: 0, incr: 2, size: ctx.samres/2});
plot.PlotBuffer(ctx.impres, {scale: 10, color: ctx.legend.colors[ctx.impcolor], start: 0, incr: 2, size: ctx.samres});
plot.PlotBuffer(ctx.trans_polar, {scale: 10*Math.sqrt(ctx.samres), color: ctx.legend.colors[ctx.color], start: 0, incr: 2, size: ctx.samres/2});
plot.PlotBuffer(ctx.trans_polar, {scale: 10/Math.PI, color: ctx.legend.colors[ctx.phcolor], start: 1, incr: 2, size: ctx.samres/2});
plot.DrawLegend(ctx.legend, {x: 100, y: 15});
dctx.fillStyle = '#000000';
dctx.fillText(`Cutoff: ${ctx.nodes[0].cutoff}`, 550, 15);
dctx.fillText(`Peak: ${ctx.trans_peak}`, 550, 35);
const ctl = { x: 5, y: cnv.height - 100 };
dctx.font = 'bold 17px sans-serif';
for (const node of ctx.nodes) {
if (node.color === undefined) {
node.color = Color.Random();
node.color_dim = node.color.Dim();
node.color_light = node.color.Lighten();
}
dctx.fillStyle = node === ctx.mouse.target ? node.color : node.color_light;
dctx.beginPath();
dctx.arc(node.cutoff / ctx.samres * cnv.width, cnv.height * 0.35, 10, 0, 2*Math.PI);
dctx.fill();
dctx.fillStyle = node.color_dim;
dctx.beginPath();
dctx.arc(node.cutoff / ctx.samres * cnv.width, cnv.height * 0.35, 4, 0, 2*Math.PI);
dctx.fill();
dctx.fillStyle = dctx.strokeStyle = node.color;
dctx.text
switch (node.type) {
case NODE_LPF:
dctx.strokeRect(ctl.x, ctl.y, 38, 20);
dctx.fillText('LPF', ctl.x+3, ctl.y+17, 40);
ctl.x += 40;
break;
case NODE_HPF:
dctx.strokeRect(ctl.x, ctl.y, 38, 20);
dctx.fillText('HPF', ctl.x+3, ctl.y+17, 40);
ctl.x += 40;
break;
}
}
};
});