ffmpeg / libavcodec / fft.c @ 5509bffa
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/*


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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., 51 Franklin Street, Fifth Floor, Boston, MA 021101301 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 ff_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 = ff_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 = ff_fft_calc_sse; 
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#else

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s>fft_calc = ff_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) << (nbitsj1); 
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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 ff_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 ff_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 .. ln1 */

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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 ff_fft_calc()

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*/

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void ff_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 ff_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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