88 lines
2.4 KiB
C
88 lines
2.4 KiB
C
#include <math.h>
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#include <stdio.h>
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#include <complex.h>
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#include <stdint.h>
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#include <stdlib.h>
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#include "../wav/wav.h"
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complex float* fft(complex float* p, uint32_t N) {
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complex float w = cexpf(-2 * I * M_PI / N);
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if (N == 1)
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return p;
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complex float* pe = (complex float*)malloc(sizeof(complex float) * (N / 2));
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complex float* po = (complex float*)malloc(sizeof(complex float) * (N / 2));
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for (int i = 0; i < N - 1; i += 2) {
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pe[i / 2] = p[i];
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po[i / 2] = p[i + 1];
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}
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complex float* xe = fft(pe, N / 2);
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complex float* xo = fft(po, N / 2);
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complex float* ps = (complex float*)malloc(sizeof(complex float) * N);
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for (int i = 0; i < N / 2; i++) {
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ps[i] = xe[i] + cpowf(w, (complex float)i) * xo[i];
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ps[i + N / 2] = xe[i] - cpowf(w, (complex float)i) * xo[i];
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}
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return ps;
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}
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complex float* ifft(complex float* p, uint32_t N) {
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complex float w = ((complex float)1 / N) * cexpf(2 * I * M_PI / N);
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if (N == 1)
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return p;
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complex float* pe = (complex float*)malloc(sizeof(complex float) * (N / 2));
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complex float* po = (complex float*)malloc(sizeof(complex float) * (N / 2));
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for (int i = 0; i < N - 1; i += 2) {
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pe[i / 2] = p[i];
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po[i / 2] = p[i + 1];
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}
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complex float* xe = fft(pe, N / 2);
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complex float* xo = fft(po, N / 2);
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complex float* ps = (complex float*)malloc(sizeof(complex float) * N);
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for (int i = 0; i < N / 2; i++) {
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ps[i] = xe[i] + cpowf(w, (complex float)i) * xo[i];
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ps[i + N / 2] = xe[i] - cpowf(w, (complex float)i) * xo[i];
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}
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return ps;
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}
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int main() {
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int wav_len;
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double* wav_data = read_wav("s.wav", &wav_len);
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int fsize = 1 << (int)floorf(log2f((float)wav_len));
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complex float* cwav_data = (complex float*)malloc(sizeof(complex float) * fsize);
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for (int i = 0; i < fsize; i++)
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cwav_data[i] = (complex float)wav_data[i];
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complex float* ft = fft(cwav_data, fsize);
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FILE *gnuplot = popen("gnuplot -persistent", "w");
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fprintf(gnuplot, "set title 'fft'\n");
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fprintf(gnuplot, "set logscale x\n");
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fprintf(gnuplot, "set logscale y\n");
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fprintf(gnuplot, "plot '-' with linespoints title 'fft'\n");
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for (int i = 0; i < fsize; i++) {
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fprintf(gnuplot, "%f %f\n",((float)i / fsize) * (float)44100 ,cabsf(ft[i]));
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}
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fprintf(gnuplot, "e\n");
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pclose(gnuplot);
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return 0;
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}
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