ref: dd88a3bf36323b1917aad54943766529bcfbe9d0
dir: /modules/scrambler.c/
/* This code is placed in the public domain. */ #include <math.h> #include "soundpipe.h" #include "kiss_fftr.h" #ifndef M_PI #define M_PI 3.14159265358979323846 #endif int sp_gen_scrambler(sp_data *sp, sp_ftbl *src, sp_ftbl **dest) { uint32_t size; sp_ftbl *dst; kiss_fftr_cfg fft, ifft; kiss_fft_cpx *tmp; uint32_t i; SPFLOAT mag, phs; SPFLOAT max; SPFLOAT val; size = (src->size % 2 == 0) ? src->size : src->size - 1; sp_ftbl_create(sp, &dst, size); /* set up kissfft */ fft = kiss_fftr_alloc(size, 0, NULL, NULL); ifft = kiss_fftr_alloc(size, 1, NULL, NULL); tmp = malloc(sizeof(kiss_fft_cpx) * size); memset(tmp, 0, sizeof(SPFLOAT) * size); kiss_fftr(fft, src->tbl, tmp); for(i = 0; i < size / 2; i++) { mag = sqrt(tmp[i].r * tmp[i].r + tmp[i].i * tmp[i].i) / size; phs = ((SPFLOAT)sp_rand(sp) / SP_RANDMAX) * 2 * M_PI; tmp[i].r = mag * cos(phs); tmp[i].i = mag * sin(phs); } tmp[0].r = 0; tmp[0].i = 0; tmp[size / 2 - 1].r = 0; tmp[size / 2 - 1].i = 0; kiss_fftri(ifft, tmp, dst->tbl); max = -1; val = 0; for(i = 0; i < size; i++) { val = fabs(dst->tbl[i]); if(val > max) { max = val; } } for(i = 0; i < size; i++) { dst->tbl[i] /= max; } kiss_fftr_free(fft); kiss_fftr_free(ifft); KISS_FFT_FREE(tmp); *dest = dst; return SP_OK; }