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 #include "dsputil.h"
  20
  21 /**
  22  * The size of the FFT is 2^nbits. If inverse is TRUE, inverse FFT is
  23  * done
  24  */
  25 int fft_init(FFTContext *s, int nbits, int inverse)
  26 {
  27     int i, j, m, n;
  28     float alpha, c1, s1, s2;
  29
  30     s->nbits = nbits;
  31     n = 1 << nbits;
  32
  33     s->exptab = av_malloc((n / 2) * sizeof(FFTComplex));
  34     if (!s->exptab)
  35         goto fail;
  36     s->revtab = av_malloc(n * sizeof(uint16_t));
  37     if (!s->revtab)
  38         goto fail;
  39     s->inverse = inverse;
  40
  41     s2 = inverse ? 1.0 : -1.0;
  42
  43     for(i=0;i<(n/2);i++) {
  44         alpha = 2 * M_PI * (float)i / (float)n;
  45         c1 = cos(alpha);
  46         s1 = sin(alpha) * s2;
  47         s->exptab[i].re = c1;
  48         s->exptab[i].im = s1;
  49     }
  50     s->fft_calc = fft_calc_c;
  51     s->exptab1 = NULL;
  52
  53     /* compute constant table for HAVE_SSE version */
  54 #if defined(HAVE_MMX) && defined(HAVE_BUILTIN_VECTOR)
  55     if (mm_support() & MM_SSE) {
  56         int np, nblocks, np2, l;
  57         FFTComplex *q;
  58
  59         np = 1 << nbits;
  60         nblocks = np >> 3;
  61         np2 = np >> 1;
  62         s->exptab1 = av_malloc(np * 2 * sizeof(FFTComplex));
  63         if (!s->exptab1)
  64             goto fail;
  65         q = s->exptab1;
  66         do {
  67             for(l = 0; l < np2; l += 2 * nblocks) {
  68                 *q++ = s->exptab[l];
  69                 *q++ = s->exptab[l + nblocks];
  70
  71                 q->re = -s->exptab[l].im;
  72                 q->im = s->exptab[l].re;
  73                 q++;
  74                 q->re = -s->exptab[l + nblocks].im;
  75                 q->im = s->exptab[l + nblocks].re;
  76                 q++;
  77             }
  78             nblocks = nblocks >> 1;
  79         } while (nblocks != 0);
  80         av_freep(&s->exptab);
  81         s->fft_calc = fft_calc_sse;
  82     }
  83 #endif
  84
  85     /* compute bit reverse table */
  86
  87     for(i=0;i<n;i++) {
  88         m=0;
  89         for(j=0;j<nbits;j++) {
  90             m |= ((i >> j) & 1) << (nbits-j-1);
  91         }
  92         s->revtab[i]=m;
  93     }
  94     return 0;
  95  fail:
  96     av_freep(&s->revtab);
  97     av_freep(&s->exptab);
  98     av_freep(&s->exptab1);
  99     return -1;
 100 }
 101
 102 /* butter fly op */
 103 #define BF(pre, pim, qre, qim, pre1, pim1, qre1, qim1) \
 104 {\
 105   FFTSample ax, ay, bx, by;\
 106   bx=pre1;\
 107   by=pim1;\
 108   ax=qre1;\
 109   ay=qim1;\
 110   pre = (bx + ax);\
 111   pim = (by + ay);\
 112   qre = (bx - ax);\
 113   qim = (by - ay);\
 114 }
 115
 116 #define MUL16(a,b) ((a) * (b))
 117
 118 #define CMUL(pre, pim, are, aim, bre, bim) \
 119 {\
 120    pre = (MUL16(are, bre) - MUL16(aim, bim));\
 121    pim = (MUL16(are, bim) + MUL16(bre, aim));\
 122 }
 123
 124 /**
 125  * Do a complex FFT with the parameters defined in fft_init(). The
 126  * input data must be permuted before with s->revtab table. No
 127  * 1.0/sqrt(n) normalization is done.
 128  */
 129 void fft_calc_c(FFTContext *s, FFTComplex *z)
 130 {
 131     int ln = s->nbits;
 132     int j, np, np2;
 133     int nblocks, nloops;
 134     register FFTComplex *p, *q;
 135     FFTComplex *exptab = s->exptab;
 136     int l;
 137     FFTSample tmp_re, tmp_im;
 138
 139     np = 1 << ln;
 140
 141     /* pass 0 */
 142
 143     p=&z[0];
 144     j=(np >> 1);
 145     do {
 146         BF(p[0].re, p[0].im, p[1].re, p[1].im,
 147            p[0].re, p[0].im, p[1].re, p[1].im);
 148         p+=2;
 149     } while (--j != 0);
 150
 151     /* pass 1 */
 152
 153
 154     p=&z[0];
 155     j=np >> 2;
 156     if (s->inverse) {
 157         do {
 158             BF(p[0].re, p[0].im, p[2].re, p[2].im,
 159                p[0].re, p[0].im, p[2].re, p[2].im);
 160             BF(p[1].re, p[1].im, p[3].re, p[3].im,
 161                p[1].re, p[1].im, -p[3].im, p[3].re);
 162             p+=4;
 163         } while (--j != 0);
 164     } else {
 165         do {
 166             BF(p[0].re, p[0].im, p[2].re, p[2].im,
 167                p[0].re, p[0].im, p[2].re, p[2].im);
 168             BF(p[1].re, p[1].im, p[3].re, p[3].im,
 169                p[1].re, p[1].im, p[3].im, -p[3].re);
 170             p+=4;
 171         } while (--j != 0);
 172     }
 173     /* pass 2 .. ln-1 */
 174
 175     nblocks = np >> 3;
 176     nloops = 1 << 2;
 177     np2 = np >> 1;
 178     do {
 179         p = z;
 180         q = z + nloops;
 181         for (j = 0; j < nblocks; ++j) {
 182             BF(p->re, p->im, q->re, q->im,
 183                p->re, p->im, q->re, q->im);
 184
 185             p++;
 186             q++;
 187             for(l = nblocks; l < np2; l += nblocks) {
 188                 CMUL(tmp_re, tmp_im, exptab[l].re, exptab[l].im, q->re, q->im);
 189                 BF(p->re, p->im, q->re, q->im,
 190                    p->re, p->im, tmp_re, tmp_im);
 191                 p++;
 192                 q++;
 193             }
 194
 195             p += nloops;
 196             q += nloops;
 197         }
 198         nblocks = nblocks >> 1;
 199         nloops = nloops << 1;
 200     } while (nblocks != 0);
 201 }
 202
 203 /**
 204  * Do the permutation needed BEFORE calling fft_calc()
 205  */
 206 void fft_permute(FFTContext *s, FFTComplex *z)
 207 {
 208     int j, k, np;
 209     FFTComplex tmp;
 210     const uint16_t *revtab = s->revtab;
 211
 212     /* reverse */
 213     np = 1 << s->nbits;
 214     for(j=0;j<np;j++) {
 215         k = revtab[j];
 216         if (k < j) {
 217             tmp = z[k];
 218             z[k] = z[j];
 219             z[j] = tmp;
 220         }
 221     }
 222 }
 223
 224 void fft_end(FFTContext *s)
 225 {
 226     av_freep(&s->revtab);
 227     av_freep(&s->exptab);
 228     av_freep(&s->exptab1);
 229 }
 230