quicktime/ffmpeg/libavcodec/fft.c

   1 /*
   2  * FFT/IFFT transforms
   3  * Copyright (c) 2002 Fabrice Bellard.
   4  *
   5  * This library is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU Lesser General Public
   7  * License as published by the Free Software Foundation; either
   8  * version 2 of the License, or (at your option) any later version.
   9  *
  10  * This library is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  * Lesser General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU Lesser General Public
  16  * License along with this library; if not, write to the Free Software
  17  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  18  */
  19
  20 /**
  21  * @file fft.c
  22  * FFT/IFFT transforms.
  23  */
  24
  25 #include "dsputil.h"
  26
  27 /**
  28  * The size of the FFT is 2^nbits. If inverse is TRUE, inverse FFT is
  29  * done
  30  */
  31 int ff_fft_init(FFTContext *s, int nbits, int inverse)
  32 {
  33     int i, j, m, n;
  34     float alpha, c1, s1, s2;
  35
  36     s->nbits = nbits;
  37     n = 1 << nbits;
  38
  39     s->exptab = av_malloc((n / 2) * sizeof(FFTComplex));
  40     if (!s->exptab)
  41         goto fail;
  42     s->revtab = av_malloc(n * sizeof(uint16_t));
  43     if (!s->revtab)
  44         goto fail;
  45     s->inverse = inverse;
  46
  47     s2 = inverse ? 1.0 : -1.0;
  48
  49     for(i=0;i<(n/2);i++) {
  50         alpha = 2 * M_PI * (float)i / (float)n;
  51         c1 = cos(alpha);
  52         s1 = sin(alpha) * s2;
  53         s->exptab[i].re = c1;
  54         s->exptab[i].im = s1;
  55     }
  56     s->fft_calc = ff_fft_calc_c;
  57     s->exptab1 = NULL;
  58
  59     /* compute constant table for HAVE_SSE version */
  60 #if (defined(HAVE_MMX) && defined(HAVE_BUILTIN_VECTOR)) || defined(HAVE_ALTIVEC)
  61     {
  62         int has_vectors = 0;
  63
  64 #if defined(HAVE_MMX)
  65         has_vectors = mm_support() & MM_SSE;
  66 #endif
  67 #if defined(HAVE_ALTIVEC) && !defined(ALTIVEC_USE_REFERENCE_C_CODE)
  68         has_vectors = mm_support() & MM_ALTIVEC;
  69 #endif
  70         if (has_vectors) {
  71             int np, nblocks, np2, l;
  72             FFTComplex *q;
  73
  74             np = 1 << nbits;
  75             nblocks = np >> 3;
  76             np2 = np >> 1;
  77             s->exptab1 = av_malloc(np * 2 * sizeof(FFTComplex));
  78             if (!s->exptab1)
  79                 goto fail;
  80             q = s->exptab1;
  81             do {
  82                 for(l = 0; l < np2; l += 2 * nblocks) {
  83                     *q++ = s->exptab[l];
  84                     *q++ = s->exptab[l + nblocks];
  85
  86                     q->re = -s->exptab[l].im;
  87                     q->im = s->exptab[l].re;
  88                     q++;
  89                     q->re = -s->exptab[l + nblocks].im;
  90                     q->im = s->exptab[l + nblocks].re;
  91                     q++;
  92                 }
  93                 nblocks = nblocks >> 1;
  94             } while (nblocks != 0);
  95             av_freep(&s->exptab);
  96 #if defined(HAVE_MMX)
  97             s->fft_calc = ff_fft_calc_sse;
  98 #else
  99             s->fft_calc = ff_fft_calc_altivec;
 100 #endif
 101         }
 102     }
 103 #endif
 104
 105     /* compute bit reverse table */
 106
 107     for(i=0;i<n;i++) {
 108         m=0;
 109         for(j=0;j<nbits;j++) {
 110             m |= ((i >> j) & 1) << (nbits-j-1);
 111         }
 112         s->revtab[i]=m;
 113     }
 114     return 0;
 115  fail:
 116     av_freep(&s->revtab);
 117     av_freep(&s->exptab);
 118     av_freep(&s->exptab1);
 119     return -1;
 120 }
 121
 122 /* butter fly op */
 123 #define BF(pre, pim, qre, qim, pre1, pim1, qre1, qim1) \
 124 {\
 125   FFTSample ax, ay, bx, by;\
 126   bx=pre1;\
 127   by=pim1;\
 128   ax=qre1;\
 129   ay=qim1;\
 130   pre = (bx + ax);\
 131   pim = (by + ay);\
 132   qre = (bx - ax);\
 133   qim = (by - ay);\
 134 }
 135
 136 #define MUL16(a,b) ((a) * (b))
 137
 138 #define CMUL(pre, pim, are, aim, bre, bim) \
 139 {\
 140    pre = (MUL16(are, bre) - MUL16(aim, bim));\
 141    pim = (MUL16(are, bim) + MUL16(bre, aim));\
 142 }
 143
 144 /**
 145  * Do a complex FFT with the parameters defined in ff_fft_init(). The
 146  * input data must be permuted before with s->revtab table. No
 147  * 1.0/sqrt(n) normalization is done.
 148  */
 149 void ff_fft_calc_c(FFTContext *s, FFTComplex *z)
 150 {
 151     int ln = s->nbits;
 152     int j, np, np2;
 153     int nblocks, nloops;
 154     register FFTComplex *p, *q;
 155     FFTComplex *exptab = s->exptab;
 156     int l;
 157     FFTSample tmp_re, tmp_im;
 158
 159     np = 1 << ln;
 160
 161     /* pass 0 */
 162
 163     p=&z[0];
 164     j=(np >> 1);
 165     do {
 166         BF(p[0].re, p[0].im, p[1].re, p[1].im,
 167            p[0].re, p[0].im, p[1].re, p[1].im);
 168         p+=2;
 169     } while (--j != 0);
 170
 171     /* pass 1 */
 172
 173
 174     p=&z[0];
 175     j=np >> 2;
 176     if (s->inverse) {
 177         do {
 178             BF(p[0].re, p[0].im, p[2].re, p[2].im,
 179                p[0].re, p[0].im, p[2].re, p[2].im);
 180             BF(p[1].re, p[1].im, p[3].re, p[3].im,
 181                p[1].re, p[1].im, -p[3].im, p[3].re);
 182             p+=4;
 183         } while (--j != 0);
 184     } else {
 185         do {
 186             BF(p[0].re, p[0].im, p[2].re, p[2].im,
 187                p[0].re, p[0].im, p[2].re, p[2].im);
 188             BF(p[1].re, p[1].im, p[3].re, p[3].im,
 189                p[1].re, p[1].im, p[3].im, -p[3].re);
 190             p+=4;
 191         } while (--j != 0);
 192     }
 193     /* pass 2 .. ln-1 */
 194
 195     nblocks = np >> 3;
 196     nloops = 1 << 2;
 197     np2 = np >> 1;
 198     do {
 199         p = z;
 200         q = z + nloops;
 201         for (j = 0; j < nblocks; ++j) {
 202             BF(p->re, p->im, q->re, q->im,
 203                p->re, p->im, q->re, q->im);
 204
 205             p++;
 206             q++;
 207             for(l = nblocks; l < np2; l += nblocks) {
 208                 CMUL(tmp_re, tmp_im, exptab[l].re, exptab[l].im, q->re, q->im);
 209                 BF(p->re, p->im, q->re, q->im,
 210                    p->re, p->im, tmp_re, tmp_im);
 211                 p++;
 212                 q++;
 213             }
 214
 215             p += nloops;
 216             q += nloops;
 217         }
 218         nblocks = nblocks >> 1;
 219         nloops = nloops << 1;
 220     } while (nblocks != 0);
 221 }
 222
 223 /**
 224  * Do the permutation needed BEFORE calling ff_fft_calc()
 225  */
 226 void ff_fft_permute(FFTContext *s, FFTComplex *z)
 227 {
 228     int j, k, np;
 229     FFTComplex tmp;
 230     const uint16_t *revtab = s->revtab;
 231
 232     /* reverse */
 233     np = 1 << s->nbits;
 234     for(j=0;j<np;j++) {
 235         k = revtab[j];
 236         if (k < j) {
 237             tmp = z[k];
 238             z[k] = z[j];
 239             z[j] = tmp;
 240         }
 241     }
 242 }
 243
 244 void ff_fft_end(FFTContext *s)
 245 {
 246     av_freep(&s->revtab);
 247     av_freep(&s->exptab);
 248     av_freep(&s->exptab1);
 249 }
 250