RepoMirrors
/
ffmpeg
mirror of https://git.ffmpeg.org/ffmpeg.git
1
0
Fork 0
Code Issues Projects Releases Wiki Activity
ffmpeg/libavcodec/fft.c

271 lines
6.8 KiB
C
Raw Blame History

/*
* FFT/IFFT transforms
* Copyright (c) 2002 Fabrice Bellard.
*
* This library 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 of the License, or (at your option) any later version.
*
* This library 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 this library; 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->exptab1 = NULL;
/* compute constant table for HAVE_SSE version */
#if (defined(HAVE_MMX) && (defined(HAVE_BUILTIN_VECTOR) || defined(HAVE_MM3DNOW))) || defined(HAVE_ALTIVEC)
{
int has_vectors = 0;
#if defined(HAVE_MMX)
#ifdef HAVE_MM3DNOW
has_vectors = mm_support() & (MM_3DNOW | MM_3DNOWEXT | MM_SSE | MM_SSE2);
#else
has_vectors = mm_support() & (MM_SSE | MM_SSE2);
#endif
#endif
#if defined(HAVE_ALTIVEC) && !defined(ALTIVEC_USE_REFERENCE_C_CODE)
has_vectors = mm_support() & MM_ALTIVEC;
#endif
if (has_vectors) {
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);
#if defined(HAVE_MMX)
#ifdef HAVE_MM3DNOW
if (has_vectors & MM_3DNOWEXT)
/* 3DNowEx for Athlon(XP) */
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;
#endif
#ifdef HAVE_BUILTIN_VECTOR
if (has_vectors & MM_SSE2)
/* SSE for P4/K8 */
s->fft_calc = ff_fft_calc_sse;
else if ((has_vectors & MM_SSE) &&
s->fft_calc == ff_fft_calc_c)
/* SSE for P3 */
s->fft_calc = ff_fft_calc_sse;
#endif
#else /* HAVE_MMX */
s->fft_calc = ff_fft_calc_altivec;
#endif
}
}
#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);
}
Reference in New Issue View Git Blame Copy Permalink