/* * FFT/IFFT transforms * Copyright (c) 2002 Fabrice Bellard. * * This file is part of FFmpeg. * * FFmpeg is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2.1 of the License, or (at your option) any later version. * * FFmpeg is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with FFmpeg; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ /** * @file fft.c * FFT/IFFT transforms. */ #include "dsputil.h" /** * The size of the FFT is 2^nbits. If inverse is TRUE, inverse FFT is * done */ int ff_fft_init(FFTContext *s, int nbits, int inverse) { int i, j, m, n; float alpha, c1, s1, s2; s->nbits = nbits; n = 1 << nbits; s->exptab = av_malloc((n / 2) * sizeof(FFTComplex)); if (!s->exptab) goto fail; s->revtab = av_malloc(n * sizeof(uint16_t)); if (!s->revtab) goto fail; s->inverse = inverse; s2 = inverse ? 1.0 : -1.0; for(i=0;i<(n/2);i++) { alpha = 2 * M_PI * (float)i / (float)n; c1 = cos(alpha); s1 = sin(alpha) * s2; s->exptab[i].re = c1; s->exptab[i].im = s1; } s->fft_calc = ff_fft_calc_c; s->imdct_calc = ff_imdct_calc; s->exptab1 = NULL; /* compute constant table for HAVE_SSE version */ #if defined(HAVE_MMX) \ || (defined(HAVE_ALTIVEC) && !defined(ALTIVEC_USE_REFERENCE_C_CODE)) { int has_vectors = mm_support(); if (has_vectors) { #if defined(HAVE_MMX) if (has_vectors & MM_3DNOWEXT) { /* 3DNowEx for K7/K8 */ s->imdct_calc = ff_imdct_calc_3dn2; s->fft_calc = ff_fft_calc_3dn2; } else if (has_vectors & MM_3DNOW) { /* 3DNow! for K6-2/3 */ s->fft_calc = ff_fft_calc_3dn; } else if (has_vectors & MM_SSE) { /* SSE for P3/P4 */ s->imdct_calc = ff_imdct_calc_sse; s->fft_calc = ff_fft_calc_sse; } #else /* HAVE_MMX */ if (has_vectors & MM_ALTIVEC) s->fft_calc = ff_fft_calc_altivec; #endif } if (s->fft_calc != ff_fft_calc_c) { int np, nblocks, np2, l; FFTComplex *q; np = 1 << nbits; nblocks = np >> 3; np2 = np >> 1; s->exptab1 = av_malloc(np * 2 * sizeof(FFTComplex)); if (!s->exptab1) goto fail; q = s->exptab1; do { for(l = 0; l < np2; l += 2 * nblocks) { *q++ = s->exptab[l]; *q++ = s->exptab[l + nblocks]; q->re = -s->exptab[l].im; q->im = s->exptab[l].re; q++; q->re = -s->exptab[l + nblocks].im; q->im = s->exptab[l + nblocks].re; q++; } nblocks = nblocks >> 1; } while (nblocks != 0); av_freep(&s->exptab); } } #endif /* compute bit reverse table */ for(i=0;i<n;i++) { m=0; for(j=0;j<nbits;j++) { m |= ((i >> j) & 1) << (nbits-j-1); } s->revtab[i]=m; } return 0; fail: av_freep(&s->revtab); av_freep(&s->exptab); av_freep(&s->exptab1); return -1; } /* butter fly op */ #define BF(pre, pim, qre, qim, pre1, pim1, qre1, qim1) \ {\ FFTSample ax, ay, bx, by;\ bx=pre1;\ by=pim1;\ ax=qre1;\ ay=qim1;\ pre = (bx + ax);\ pim = (by + ay);\ qre = (bx - ax);\ qim = (by - ay);\ } #define MUL16(a,b) ((a) * (b)) #define CMUL(pre, pim, are, aim, bre, bim) \ {\ pre = (MUL16(are, bre) - MUL16(aim, bim));\ pim = (MUL16(are, bim) + MUL16(bre, aim));\ } /** * Do a complex FFT with the parameters defined in ff_fft_init(). The * input data must be permuted before with s->revtab table. No * 1.0/sqrt(n) normalization is done. */ void ff_fft_calc_c(FFTContext *s, FFTComplex *z) { int ln = s->nbits; int j, np, np2; int nblocks, nloops; register FFTComplex *p, *q; FFTComplex *exptab = s->exptab; int l; FFTSample tmp_re, tmp_im; np = 1 << ln; /* pass 0 */ p=&z[0]; j=(np >> 1); do { BF(p[0].re, p[0].im, p[1].re, p[1].im, p[0].re, p[0].im, p[1].re, p[1].im); p+=2; } while (--j != 0); /* pass 1 */ p=&z[0]; j=np >> 2; if (s->inverse) { do { BF(p[0].re, p[0].im, p[2].re, p[2].im, p[0].re, p[0].im, p[2].re, p[2].im); BF(p[1].re, p[1].im, p[3].re, p[3].im, p[1].re, p[1].im, -p[3].im, p[3].re); p+=4; } while (--j != 0); } else { do { BF(p[0].re, p[0].im, p[2].re, p[2].im, p[0].re, p[0].im, p[2].re, p[2].im); BF(p[1].re, p[1].im, p[3].re, p[3].im, p[1].re, p[1].im, p[3].im, -p[3].re); p+=4; } while (--j != 0); } /* pass 2 .. ln-1 */ nblocks = np >> 3; nloops = 1 << 2; np2 = np >> 1; do { p = z; q = z + nloops; for (j = 0; j < nblocks; ++j) { BF(p->re, p->im, q->re, q->im, p->re, p->im, q->re, q->im); p++; q++; for(l = nblocks; l < np2; l += nblocks) { CMUL(tmp_re, tmp_im, exptab[l].re, exptab[l].im, q->re, q->im); BF(p->re, p->im, q->re, q->im, p->re, p->im, tmp_re, tmp_im); p++; q++; } p += nloops; q += nloops; } nblocks = nblocks >> 1; nloops = nloops << 1; } while (nblocks != 0); } /** * Do the permutation needed BEFORE calling ff_fft_calc() */ void ff_fft_permute(FFTContext *s, FFTComplex *z) { int j, k, np; FFTComplex tmp; const uint16_t *revtab = s->revtab; /* reverse */ np = 1 << s->nbits; for(j=0;j<np;j++) { k = revtab[j]; if (k < j) { tmp = z[k]; z[k] = z[j]; z[j] = tmp; } } } void ff_fft_end(FFTContext *s) { av_freep(&s->revtab); av_freep(&s->exptab); av_freep(&s->exptab1); }