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test_fft.html
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test_fft.html
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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width,initial-scale=1">
<title>Oscilloscope</title>
<script src="fft_testdata.js"></script>
</script>
<script>
window.addEventListener('load', function() {
re = x.slice(0, 512);
im = new Float32Array(512);
miniFFT(re, im);
P = [];
for(var i = 0; i < re.length; i++)
P.push(re[i] * re[i] + im[i] * im[i]);
document.body.innerHTML = P.join(',')
});
miniFFT = function(re, im) {
var N = re.length;
var i, j, h, k;
for (i = 0; i < N; i++) {
for(j = 0, h = i, k = N; k >>= 1; h >>= 1){ // eslint-disable-line no-cond-assign
j = (j << 1) | (h & 1);
}
if (j > i) {
re[j] = [re[i], re[i] = re[j]][0];
im[j] = [im[i], im[i] = im[j]][0];
}
}
for(var hN = 1; hN * 2 <= N; hN *= 2){
for (i = 0; i < N; i += hN * 2){
for (j = i; j < i + hN; j++) {
var cos = Math.cos(Math.PI * (j - i) / hN);
var sin = Math.sin(Math.PI * (j - i) / hN);
var tre = re[j+hN] * cos + im[j+hN] * sin;
var tim = -re[j+hN] * sin + im[j+hN] * cos;
re[j + hN] = re[j] - tre; im[j + hN] = im[j] - tim;
re[j] += tre; im[j] += tim;
}
}
}
};
</script>
</head>
<body>
</body>
</html>