ffmpeg做fft

#define inline _inline#include <math.h>#include <stdio.h>#include <stdlib.h>#include <string.h>#include "libavcodec/fft.h"int main(){    float a[8] = { 0, 1, 2, 3, 4, 5, 6, 7 };    FFTComplex *tab;    FFTContext s;    int i;    int do_inverse = 0;    int fft_nbits = 3, fft_size;    fft_size = 1 << fft_nbits;    tab = av_malloc_array(fft_size, sizeof(FFTComplex));    if (!(tab))        goto cleanup;    ff_fft_init(&s, fft_nbits, do_inverse);    for (i = 0; i < fft_size; i++) {        tab[i].re = a[i];        tab[i].im = 0;    }    s.fft_permute(&s, tab);    s.fft_calc(&s, tab);    ff_fft_end(&s);    for (i = 0; i < fft_size; i++)    {        printf("%f %fi\n", tab[i].re, tab[i].im);    }    cleanup:    av_free(tab);    return 0;}