mirror of https://git.ffmpeg.org/ffmpeg.git
251 lines
6.1 KiB
C
251 lines
6.1 KiB
C
/*
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* FFT/IFFT transforms
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* Copyright (c) 2002 Fabrice Bellard.
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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/**
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* @file fft.c
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* FFT/IFFT transforms.
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*/
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#include "dsputil.h"
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/**
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* The size of the FFT is 2^nbits. If inverse is TRUE, inverse FFT is
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* done
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*/
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int fft_init(FFTContext *s, int nbits, int inverse)
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{
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int i, j, m, n;
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float alpha, c1, s1, s2;
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s->nbits = nbits;
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n = 1 << nbits;
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s->exptab = av_malloc((n / 2) * sizeof(FFTComplex));
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if (!s->exptab)
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goto fail;
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s->revtab = av_malloc(n * sizeof(uint16_t));
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if (!s->revtab)
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goto fail;
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s->inverse = inverse;
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s2 = inverse ? 1.0 : -1.0;
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for(i=0;i<(n/2);i++) {
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alpha = 2 * M_PI * (float)i / (float)n;
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c1 = cos(alpha);
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s1 = sin(alpha) * s2;
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s->exptab[i].re = c1;
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s->exptab[i].im = s1;
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}
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s->fft_calc = fft_calc_c;
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s->exptab1 = NULL;
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/* compute constant table for HAVE_SSE version */
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#if (defined(HAVE_MMX) && defined(HAVE_BUILTIN_VECTOR)) || defined(HAVE_ALTIVEC)
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{
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int has_vectors = 0;
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#if defined(HAVE_MMX)
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has_vectors = mm_support() & MM_SSE;
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#endif
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#if defined(HAVE_ALTIVEC) && !defined(ALTIVEC_USE_REFERENCE_C_CODE)
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has_vectors = mm_support() & MM_ALTIVEC;
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#endif
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if (has_vectors) {
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int np, nblocks, np2, l;
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FFTComplex *q;
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np = 1 << nbits;
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nblocks = np >> 3;
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np2 = np >> 1;
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s->exptab1 = av_malloc(np * 2 * sizeof(FFTComplex));
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if (!s->exptab1)
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goto fail;
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q = s->exptab1;
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do {
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for(l = 0; l < np2; l += 2 * nblocks) {
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*q++ = s->exptab[l];
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*q++ = s->exptab[l + nblocks];
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q->re = -s->exptab[l].im;
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q->im = s->exptab[l].re;
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q++;
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q->re = -s->exptab[l + nblocks].im;
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q->im = s->exptab[l + nblocks].re;
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q++;
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}
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nblocks = nblocks >> 1;
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} while (nblocks != 0);
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av_freep(&s->exptab);
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#if defined(HAVE_MMX)
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s->fft_calc = fft_calc_sse;
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#else
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s->fft_calc = fft_calc_altivec;
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#endif
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}
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}
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#endif
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/* compute bit reverse table */
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for(i=0;i<n;i++) {
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m=0;
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for(j=0;j<nbits;j++) {
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m |= ((i >> j) & 1) << (nbits-j-1);
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}
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s->revtab[i]=m;
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}
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return 0;
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fail:
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av_freep(&s->revtab);
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av_freep(&s->exptab);
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av_freep(&s->exptab1);
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return -1;
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}
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/* butter fly op */
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#define BF(pre, pim, qre, qim, pre1, pim1, qre1, qim1) \
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{\
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FFTSample ax, ay, bx, by;\
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bx=pre1;\
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by=pim1;\
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ax=qre1;\
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ay=qim1;\
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pre = (bx + ax);\
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pim = (by + ay);\
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qre = (bx - ax);\
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qim = (by - ay);\
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}
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#define MUL16(a,b) ((a) * (b))
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#define CMUL(pre, pim, are, aim, bre, bim) \
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{\
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pre = (MUL16(are, bre) - MUL16(aim, bim));\
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pim = (MUL16(are, bim) + MUL16(bre, aim));\
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}
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/**
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* Do a complex FFT with the parameters defined in fft_init(). The
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* input data must be permuted before with s->revtab table. No
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* 1.0/sqrt(n) normalization is done.
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*/
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void fft_calc_c(FFTContext *s, FFTComplex *z)
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{
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int ln = s->nbits;
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int j, np, np2;
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int nblocks, nloops;
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register FFTComplex *p, *q;
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FFTComplex *exptab = s->exptab;
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int l;
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FFTSample tmp_re, tmp_im;
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np = 1 << ln;
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/* pass 0 */
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p=&z[0];
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j=(np >> 1);
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do {
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BF(p[0].re, p[0].im, p[1].re, p[1].im,
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p[0].re, p[0].im, p[1].re, p[1].im);
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p+=2;
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} while (--j != 0);
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/* pass 1 */
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p=&z[0];
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j=np >> 2;
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if (s->inverse) {
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do {
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BF(p[0].re, p[0].im, p[2].re, p[2].im,
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p[0].re, p[0].im, p[2].re, p[2].im);
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BF(p[1].re, p[1].im, p[3].re, p[3].im,
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p[1].re, p[1].im, -p[3].im, p[3].re);
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p+=4;
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} while (--j != 0);
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} else {
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do {
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BF(p[0].re, p[0].im, p[2].re, p[2].im,
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p[0].re, p[0].im, p[2].re, p[2].im);
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BF(p[1].re, p[1].im, p[3].re, p[3].im,
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p[1].re, p[1].im, p[3].im, -p[3].re);
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p+=4;
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} while (--j != 0);
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}
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/* pass 2 .. ln-1 */
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nblocks = np >> 3;
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nloops = 1 << 2;
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np2 = np >> 1;
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do {
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p = z;
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q = z + nloops;
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for (j = 0; j < nblocks; ++j) {
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BF(p->re, p->im, q->re, q->im,
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p->re, p->im, q->re, q->im);
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p++;
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q++;
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for(l = nblocks; l < np2; l += nblocks) {
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CMUL(tmp_re, tmp_im, exptab[l].re, exptab[l].im, q->re, q->im);
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BF(p->re, p->im, q->re, q->im,
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p->re, p->im, tmp_re, tmp_im);
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p++;
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q++;
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}
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p += nloops;
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q += nloops;
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}
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nblocks = nblocks >> 1;
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nloops = nloops << 1;
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} while (nblocks != 0);
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}
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/**
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* Do the permutation needed BEFORE calling fft_calc()
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*/
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void fft_permute(FFTContext *s, FFTComplex *z)
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{
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int j, k, np;
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FFTComplex tmp;
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const uint16_t *revtab = s->revtab;
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/* reverse */
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np = 1 << s->nbits;
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for(j=0;j<np;j++) {
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k = revtab[j];
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if (k < j) {
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tmp = z[k];
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z[k] = z[j];
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z[j] = tmp;
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}
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}
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}
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void fft_end(FFTContext *s)
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{
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av_freep(&s->revtab);
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av_freep(&s->exptab);
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av_freep(&s->exptab1);
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}
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