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Test jsfft
author Chris Cannam
date Thu, 01 Oct 2015 17:33:28 +0100
parents 1c027151f7ec
children b3243c84ccb3
rev   line source
Chris@1 1 <html>
Chris@2 2 <meta charset="UTF-8">
Chris@1 3 <body>
Chris@1 4 <p>If 2150 iterations of real-to-complex FFT of size 2048 takes less than 10 seconds, then we may be able to make a high quality real-time phase vocoder (just).</p>
Chris@1 5
Chris@1 6 <p>A phase-vocoder of course must use overlapped
Chris@1 7 windowed FFT (although you can choose the size, within limits), IFFT,
Chris@1 8 and cartesian-polar conversion to calculate the phase for the
Chris@1 9 instantaneous frequency.</p>
Chris@1 10
Chris@1 11 <p>A reasonable estimate of CPU cost for the whole thing is somewhere
Chris@1 12 around 10x the cost of simple non-overlapping short-time forward
Chris@1 13 Fourier transforms across the signal. </p>
Chris@1 14
Chris@1 15 <p>2150 iterations corresponds to 100 seconds of audio non-overlapped at
Chris@1 16 44.1kHz, so if that takes less than 10 second, then in theory we might
Chris@1 17 be OK.</p>
Chris@2 18
Chris@1 19 <script src="nayuki/fft.js"></script>
Chris@1 20 <script>
Chris@1 21
Chris@1 22 /* for a phase vocoder, we probably want 2048-point real-to-complex
Chris@1 23 * FFTs (if available) */
Chris@1 24
Chris@1 25 function inputReals(size) {
Chris@1 26 var result = new Array(size);
Chris@1 27 for (var i = 0; i < result.length; i++)
Chris@1 28 result[i] = (i % 20) / 10.0 - 1.0;
Chris@1 29 return result;
Chris@1 30 }
Chris@1 31
Chris@1 32 function zeroReals(size) {
Chris@1 33 var result = new Array(size);
Chris@1 34 for (var i = 0; i < result.length; i++)
Chris@1 35 result[i] = 0.0;
Chris@1 36 return result;
Chris@1 37 }
Chris@1 38
Chris@1 39 function inputReal64s(size) {
Chris@1 40 var result = new Float64Array(size);
Chris@1 41 for (var i = 0; i < result.length; i++)
Chris@1 42 result[i] = (i % 20) / 10.0 - 1.0;
Chris@1 43 return result;
Chris@1 44 }
Chris@1 45
Chris@1 46 var iterations = 2150;
Chris@1 47 var size = 2048;
Chris@1 48
Chris@1 49 var start = performance.now();
Chris@1 50
Chris@1 51 var total = 0.0;
Chris@1 52
Chris@1 53 for (var i = 0; i < iterations; ++i) {
Chris@1 54 var real = inputReals(size);
Chris@1 55 var imag = zeroReals(size);
Chris@1 56 transform(real, imag);
Chris@1 57 for (var j = 0; j < size; ++j) {
Chris@1 58 total += real[j] + imag[j];
Chris@1 59 }
Chris@1 60 }
Chris@1 61
Chris@1 62 document.write("total = " + total + "<br>");
Chris@1 63
Chris@1 64 var end = performance.now();
Chris@1 65
Chris@2 66 document.write("nayuki fft.js: " + iterations + " iterations at size " + size + " took " + (end - start) + "ms (" + (1000.0 / ((end - start) / iterations)) + " iterations/sec)<br><br>");
Chris@1 67
Chris@1 68 </script>
Chris@1 69 <script src="fft.js/lib/complex.js"></script>
Chris@1 70 <script>
Chris@1 71
Chris@1 72 var fft = new FFT.complex(size, false);
Chris@1 73
Chris@1 74 start = performance.now();
Chris@1 75
Chris@1 76 total = 0.0;
Chris@1 77
Chris@1 78 for (var i = 0; i < iterations; ++i) {
Chris@1 79 var ri = inputReal64s(size);
Chris@1 80 var co = new Float64Array(2 * size);
Chris@1 81 fft.simple(co, ri, 'real');
Chris@1 82 for (var j = 0; j < 2 * size; ++j) {
Chris@1 83 total += co[j];
Chris@1 84 }
Chris@1 85 }
Chris@1 86
Chris@1 87 document.write("total = " + total + "<br>");
Chris@1 88
Chris@1 89 var end = performance.now();
Chris@1 90
Chris@2 91 document.write("nockert fft.js: " + iterations + " iterations at size " + size + " took " + (end - start) + "ms (" + (1000.0 / ((end - start) / iterations)) + " iterations/sec)<br><br>");
Chris@1 92
Chris@1 93 </script>
Chris@2 94 <script src="jsfft/lib/complex_array.js"></script><script src="jsfft/lib/fft.js"></script>
Chris@2 95 <script>
Chris@2 96
Chris@2 97 function inputComplexArray(size) {
Chris@2 98 var result = new complex_array.ComplexArray(size);
Chris@2 99 for (var i = 0; i < size; i++) {
Chris@2 100 result.real[i] = (i % 20) / 10.0 - 1.0;
Chris@2 101 result.imag[i] = 0.0;
Chris@2 102 }
Chris@2 103 return result;
Chris@2 104 }
Chris@2 105
Chris@2 106 start = performance.now();
Chris@2 107
Chris@2 108 total = 0.0;
Chris@2 109
Chris@2 110 for (var i = 0; i < iterations; ++i) {
Chris@2 111 var ci = inputComplexArray(size);
Chris@2 112 var co = ci.FFT();
Chris@2 113 for (var j = 0; j < size; ++j) {
Chris@2 114 total += co.real[j] + co.imag[j];
Chris@2 115 }
Chris@2 116 }
Chris@2 117
Chris@2 118 document.write("total = " + total + "<br>");
Chris@2 119
Chris@2 120 var end = performance.now();
Chris@2 121
Chris@2 122 document.write("dntj jsfft: " + iterations + " iterations at size " + size + " took " + (end - start) + "ms (" + (1000.0 / ((end - start) / iterations)) + " iterations/sec)<br><br>");
Chris@2 123
Chris@2 124 </script>
Chris@2 125
Chris@1 126 </body>
Chris@1 127