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new generic FFT/MDCT code for audio codecs 

Originally committed as revision 1088 to svn://svn.ffmpeg.org/ffmpeg/trunk
tags/v0.5
Fabrice Bellard 23 years ago
parent
6d29182097
commit
bb6f569072
5 changed files with 869 additions and 1 deletions
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  1. +48
    -1
      libavcodec/dsputil.h
  2. +294
    -0
      libavcodec/fft-test.c
  3. +229
    -0
      libavcodec/fft.c
  4. +128
    -0
      libavcodec/i386/fft_sse.c
  5. +170
    -0
      libavcodec/mdct.c

+ 48
- 1
libavcodec/dsputil.h View File

@@ -221,5 +221,52 @@ struct unaligned_32 { uint32_t l; } __attribute__((packed));
void get_psnr(UINT8 *orig_image[3], UINT8 *coded_image[3],
int orig_linesize[3], int coded_linesize,
AVCodecContext *avctx);

/* FFT computation */

/* NOTE: soon integer code will be added, so you must use the
FFTSample type */
typedef float FFTSample;

typedef struct FFTComplex {
FFTSample re, im;
} FFTComplex;

typedef struct FFTContext {
int nbits;
int inverse;
uint16_t *revtab;
FFTComplex *exptab;
FFTComplex *exptab1; /* only used by SSE code */
void (*fft_calc)(struct FFTContext *s, FFTComplex *z);
} FFTContext;

int fft_init(FFTContext *s, int nbits, int inverse);
void fft_permute(FFTContext *s, FFTComplex *z);
void fft_calc_c(FFTContext *s, FFTComplex *z);
void fft_calc_sse(FFTContext *s, FFTComplex *z);
static inline void fft_calc(FFTContext *s, FFTComplex *z)
{
s->fft_calc(s, z);
}
void fft_end(FFTContext *s);

/* MDCT computation */

typedef struct MDCTContext {
int n; /* size of MDCT (i.e. number of input data * 2) */
int nbits; /* n = 2^nbits */
/* pre/post rotation tables */
FFTSample *tcos;
FFTSample *tsin;
FFTContext fft;
} MDCTContext;

int mdct_init(MDCTContext *s, int nbits, int inverse);
void imdct_calc(MDCTContext *s, FFTSample *output,
const FFTSample *input, FFTSample *tmp);
void mdct_calc(MDCTContext *s, FFTSample *out,
const FFTSample *input, FFTSample *tmp);
void mdct_end(MDCTContext *s);

#endif

+ 294
- 0
libavcodec/fft-test.c View File

@@ -0,0 +1,294 @@
/* FFT and MDCT tests */
#include "dsputil.h"
#include <math.h>
#include <getopt.h>
#include <sys/time.h>

int mm_flags;

void *av_malloc(int size)
{
void *ptr;
ptr = malloc(size);
return ptr;
}

void av_free(void *ptr)
{
/* XXX: this test should not be needed on most libcs */
if (ptr)
free(ptr);
}

/* cannot call it directly because of 'void **' casting is not automatic */
void __av_freep(void **ptr)
{
av_free(*ptr);
*ptr = NULL;
}

/* reference fft */

#define MUL16(a,b) ((a) * (b))

#define CMAC(pre, pim, are, aim, bre, bim) \
{\
pre += (MUL16(are, bre) - MUL16(aim, bim));\
pim += (MUL16(are, bim) + MUL16(bre, aim));\
}

FFTComplex *exptab;

void fft_ref_init(int nbits, int inverse)
{
int n, i;
float c1, s1, alpha;

n = 1 << nbits;
exptab = av_malloc((n / 2) * sizeof(FFTComplex));

for(i=0;i<(n/2);i++) {
alpha = 2 * M_PI * (float)i / (float)n;
c1 = cos(alpha);
s1 = sin(alpha);
if (!inverse)
s1 = -s1;
exptab[i].re = c1;
exptab[i].im = s1;
}
}

void fft_ref(FFTComplex *tabr, FFTComplex *tab, int nbits)
{
int n, i, j, k, n2;
float tmp_re, tmp_im, s, c;
FFTComplex *q;

n = 1 << nbits;
n2 = n >> 1;
for(i=0;i<n;i++) {
tmp_re = 0;
tmp_im = 0;
q = tab;
for(j=0;j<n;j++) {
k = (i * j) & (n - 1);
if (k >= n2) {
c = -exptab[k - n2].re;
s = -exptab[k - n2].im;
} else {
c = exptab[k].re;
s = exptab[k].im;
}
CMAC(tmp_re, tmp_im, c, s, q->re, q->im);
q++;
}
tabr[i].re = tmp_re;
tabr[i].im = tmp_im;
}
}

void imdct_ref(float *out, float *in, int n)
{
int k, i, a;
float sum, f;

for(i=0;i<n;i++) {
sum = 0;
for(k=0;k<n/2;k++) {
a = (2 * i + 1 + (n / 2)) * (2 * k + 1);
f = cos(M_PI * a / (double)(2 * n));
sum += f * in[k];
}
out[i] = -sum;
}
}

/* NOTE: no normalisation by 1 / N is done */
void mdct_ref(float *output, float *input, int n)
{
int k, i;
float a, s;

/* do it by hand */
for(k=0;k<n/2;k++) {
s = 0;
for(i=0;i<n;i++) {
a = (2*M_PI*(2*i+1+n/2)*(2*k+1) / (4 * n));
s += input[i] * cos(a);
}
output[k] = s;
}
}


float frandom(void)
{
return (float)((random() & 0xffff) - 32768) / 32768.0;
}

INT64 gettime(void)
{
struct timeval tv;
gettimeofday(&tv,NULL);
return (INT64)tv.tv_sec * 1000000 + tv.tv_usec;
}

void check_diff(float *tab1, float *tab2, int n)
{
int i;

for(i=0;i<n;i++) {
if (fabsf(tab1[i] - tab2[i]) >= 1e-3) {
printf("ERROR %d: %f %f\n",
i, tab1[i], tab2[i]);
}
}
}


void help(void)
{
printf("usage: fft-test [-h] [-s] [-i] [-n b]\n"
"-h print this help\n"
"-s speed test\n"
"-m (I)MDCT test\n"
"-i inverse transform test\n"
"-n b set the transform size to 2^b\n"
);
exit(1);
}



int main(int argc, char **argv)
{
FFTComplex *tab, *tab1, *tab_ref;
FFTSample *tabtmp, *tab2;
int it, i, c;
int do_speed = 0;
int do_mdct = 0;
int do_inverse = 0;
FFTContext s1, *s = &s1;
MDCTContext m1, *m = &m1;
int fft_nbits, fft_size;

mm_flags = 0;
fft_nbits = 9;
for(;;) {
c = getopt(argc, argv, "hsimn:");
if (c == -1)
break;
switch(c) {
case 'h':
help();
break;
case 's':
do_speed = 1;
break;
case 'i':
do_inverse = 1;
break;
case 'm':
do_mdct = 1;
break;
case 'n':
fft_nbits = atoi(optarg);
break;
}
}

fft_size = 1 << fft_nbits;
tab = av_malloc(fft_size * sizeof(FFTComplex));
tab1 = av_malloc(fft_size * sizeof(FFTComplex));
tab_ref = av_malloc(fft_size * sizeof(FFTComplex));
tabtmp = av_malloc(fft_size / 2 * sizeof(FFTSample));
tab2 = av_malloc(fft_size * sizeof(FFTSample));

if (do_mdct) {
if (do_inverse)
printf("IMDCT");
else
printf("MDCT");
mdct_init(m, fft_nbits, do_inverse);
} else {
if (do_inverse)
printf("IFFT");
else
printf("FFT");
fft_init(s, fft_nbits, do_inverse);
fft_ref_init(fft_nbits, do_inverse);
}
printf(" %d test\n", fft_size);

/* generate random data */

for(i=0;i<fft_size;i++) {
tab1[i].re = frandom();
tab1[i].im = frandom();
}

/* checking result */
printf("Checking...\n");

if (do_mdct) {
if (do_inverse) {
imdct_ref((float *)tab_ref, (float *)tab1, fft_size);
imdct_calc(m, tab2, (float *)tab1, tabtmp);
check_diff((float *)tab_ref, tab2, fft_size);
} else {
mdct_ref((float *)tab_ref, (float *)tab1, fft_size);
mdct_calc(m, tab2, (float *)tab1, tabtmp);

check_diff((float *)tab_ref, tab2, fft_size / 2);
}
} else {
memcpy(tab, tab1, fft_size * sizeof(FFTComplex));
fft_permute(s, tab);
fft_calc(s, tab);
fft_ref(tab_ref, tab1, fft_nbits);
check_diff((float *)tab_ref, (float *)tab, fft_size * 2);
}

/* do a speed test */

if (do_speed) {
INT64 time_start, duration;
int nb_its;

printf("Speed test...\n");
/* we measure during about 1 seconds */
nb_its = 1;
for(;;) {
time_start = gettime();
for(it=0;it<nb_its;it++) {
if (do_mdct) {
if (do_inverse) {
imdct_calc(m, (float *)tab, (float *)tab1, tabtmp);
} else {
mdct_calc(m, (float *)tab, (float *)tab1, tabtmp);
}
} else {
memcpy(tab, tab1, fft_size * sizeof(FFTComplex));
fft_calc(s, tab);
}
}
duration = gettime() - time_start;
if (duration >= 1000000)
break;
nb_its *= 2;
}
printf("time: %0.1f us/transform [total time=%0.2f s its=%d]\n",
(double)duration / nb_its,
(double)duration / 1000000.0,
nb_its);
}
if (do_mdct) {
mdct_end(m);
} else {
fft_end(s);
}
return 0;
}

+ 229
- 0
libavcodec/fft.c View File

@@ -0,0 +1,229 @@
/*
* 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include "dsputil.h"

/**
* The size of the FFT is 2^nbits. If inverse is TRUE, inverse FFT is
* done
*/
int 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 = fft_calc_c;
s->exptab1 = NULL;

/* compute constant table for HAVE_SSE version */
#if defined(HAVE_MMX) && 0
if (mm_flags & MM_SSE) {
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);
}
#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 fft_init(). The
* input data must be permuted before with s->revtab table. No
* 1.0/sqrt(n) normalization is done.
*/
void 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 fft_calc()
*/
void 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 fft_end(FFTContext *s)
{
av_freep(&s->revtab);
av_freep(&s->exptab);
av_freep(&s->exptab1);
}


+ 128
- 0
libavcodec/i386/fft_sse.c View File

@@ -0,0 +1,128 @@
/*
* FFT/MDCT transform with SSE optimizations
* 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include "../dsputil.h"
#include <math.h>

#include <xmmintrin.h>

static const float p1p1p1m1[4] __attribute__((aligned(16))) =
{ 1.0, 1.0, 1.0, -1.0 };

static const float p1p1m1m1[4] __attribute__((aligned(16))) =
{ 1.0, 1.0, -1.0, -1.0 };

#if 0
static void print_v4sf(const char *str, __m128 a)
{
float *p = (float *)&a;
printf("%s: %f %f %f %f\n",
str, p[0], p[1], p[2], p[3]);
}
#endif

/* XXX: handle reverse case */
void fft_calc_sse(FFTContext *s, FFTComplex *z)
{
int ln = s->nbits;
int j, np, np2;
int nblocks, nloops;
register FFTComplex *p, *q;
FFTComplex *cptr, *cptr1;
int k;

np = 1 << ln;

{
__m128 *r, a, b, a1, c1, c2;

r = (__m128 *)&z[0];
c1 = *(__m128 *)p1p1m1m1;
c2 = *(__m128 *)p1p1p1m1;
j = (np >> 2);
do {
a = r[0];
b = _mm_shuffle_ps(a, a, _MM_SHUFFLE(1, 0, 3, 2));
a = _mm_mul_ps(a, c1);
/* do the pass 0 butterfly */
a = _mm_add_ps(a, b);

a1 = r[1];
b = _mm_shuffle_ps(a1, a1, _MM_SHUFFLE(1, 0, 3, 2));
a1 = _mm_mul_ps(a1, c1);
/* do the pass 0 butterfly */
b = _mm_add_ps(a1, b);

/* multiply third by -i */
b = _mm_shuffle_ps(b, b, _MM_SHUFFLE(2, 3, 1, 0));
b = _mm_mul_ps(b, c2);

/* do the pass 1 butterfly */
r[0] = _mm_add_ps(a, b);
r[1] = _mm_sub_ps(a, b);
r += 2;
} while (--j != 0);
}
/* pass 2 .. ln-1 */

nblocks = np >> 3;
nloops = 1 << 2;
np2 = np >> 1;

cptr1 = s->exptab1;
do {
p = z;
q = z + nloops;
j = nblocks;
do {
cptr = cptr1;
k = nloops >> 1;
do {
__m128 a, b, c, t1, t2;

a = *(__m128 *)p;
b = *(__m128 *)q;
/* complex mul */
c = *(__m128 *)cptr;
/* cre*re cim*re */
t1 = _mm_mul_ps(c,
_mm_shuffle_ps(b, b, _MM_SHUFFLE(2, 2, 0, 0)));
c = *(__m128 *)(cptr + 2);
/* -cim*im cre*im */
t2 = _mm_mul_ps(c,
_mm_shuffle_ps(b, b, _MM_SHUFFLE(3, 3, 1, 1)));
b = _mm_add_ps(t1, t2);
/* butterfly */
*(__m128 *)p = _mm_add_ps(a, b);
*(__m128 *)q = _mm_sub_ps(a, b);
p += 2;
q += 2;
cptr += 4;
} while (--k);
p += nloops;
q += nloops;
} while (--j);
cptr1 += nloops * 2;
nblocks = nblocks >> 1;
nloops = nloops << 1;
} while (nblocks != 0);
}

+ 170
- 0
libavcodec/mdct.c View File

@@ -0,0 +1,170 @@
/*
* MDCT/IMDCT 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include "dsputil.h"

/*
* init MDCT or IMDCT computation
*/
int mdct_init(MDCTContext *s, int nbits, int inverse)
{
int n, n4, i;
float alpha;

memset(s, 0, sizeof(*s));
n = 1 << nbits;
s->nbits = nbits;
s->n = n;
n4 = n >> 2;
s->tcos = malloc(n4 * sizeof(FFTSample));
if (!s->tcos)
goto fail;
s->tsin = malloc(n4 * sizeof(FFTSample));
if (!s->tsin)
goto fail;

for(i=0;i<n4;i++) {
alpha = 2 * M_PI * (i + 1.0 / 8.0) / n;
s->tcos[i] = -cos(alpha);
s->tsin[i] = -sin(alpha);
}
if (fft_init(&s->fft, s->nbits - 2, inverse) < 0)
goto fail;
return 0;
fail:
av_freep(&s->tcos);
av_freep(&s->tsin);
return -1;
}

/* complex multiplication: p = a * b */
#define CMUL(pre, pim, are, aim, bre, bim) \
{\
float _are = (are);\
float _aim = (aim);\
float _bre = (bre);\
float _bim = (bim);\
(pre) = _are * _bre - _aim * _bim;\
(pim) = _are * _bim + _aim * _bre;\
}

/**
* Compute inverse MDCT of size N = 2^nbits
* @param output N samples
* @param input N/2 samples
* @param tmp N/2 samples
*/
void imdct_calc(MDCTContext *s, FFTSample *output,
const FFTSample *input, FFTSample *tmp)
{
int k, n8, n4, n2, n, j;
const uint16_t *revtab = s->fft.revtab;
const FFTSample *tcos = s->tcos;
const FFTSample *tsin = s->tsin;
const FFTSample *in1, *in2;
FFTComplex *z = (FFTComplex *)tmp;

n = 1 << s->nbits;
n2 = n >> 1;
n4 = n >> 2;
n8 = n >> 3;

/* pre rotation */
in1 = input;
in2 = input + n2 - 1;
for(k = 0; k < n4; k++) {
j=revtab[k];
CMUL(z[j].re, z[j].im, *in2, *in1, tcos[k], tsin[k]);
in1 += 2;
in2 -= 2;
}
fft_calc(&s->fft, z);

/* post rotation + reordering */
/* XXX: optimize */
for(k = 0; k < n4; k++) {
CMUL(z[k].re, z[k].im, z[k].re, z[k].im, tcos[k], tsin[k]);
}
for(k = 0; k < n8; k++) {
output[2*k] = -z[n8 + k].im;
output[n2-1-2*k] = z[n8 + k].im;

output[2*k+1] = z[n8-1-k].re;
output[n2-1-2*k-1] = -z[n8-1-k].re;

output[n2 + 2*k]=-z[k+n8].re;
output[n-1- 2*k]=-z[k+n8].re;

output[n2 + 2*k+1]=z[n8-k-1].im;
output[n-2 - 2 * k] = z[n8-k-1].im;
}
}

/**
* Compute MDCT of size N = 2^nbits
* @param input N samples
* @param out N/2 samples
* @param tmp temporary storage of N/2 samples
*/
void mdct_calc(MDCTContext *s, FFTSample *out,
const FFTSample *input, FFTSample *tmp)
{
int i, j, n, n8, n4, n2, n3;
FFTSample re, im, re1, im1;
const uint16_t *revtab = s->fft.revtab;
const FFTSample *tcos = s->tcos;
const FFTSample *tsin = s->tsin;
FFTComplex *x = (FFTComplex *)tmp;

n = 1 << s->nbits;
n2 = n >> 1;
n4 = n >> 2;
n8 = n >> 3;
n3 = 3 * n4;

/* pre rotation */
for(i=0;i<n8;i++) {
re = -input[2*i+3*n4] - input[n3-1-2*i];
im = -input[n4+2*i] + input[n4-1-2*i];
j = revtab[i];
CMUL(x[j].re, x[j].im, re, im, -tcos[i], tsin[i]);

re = input[2*i] - input[n2-1-2*i];
im = -(input[n2+2*i] + input[n-1-2*i]);
j = revtab[n8 + i];
CMUL(x[j].re, x[j].im, re, im, -tcos[n8 + i], tsin[n8 + i]);
}

fft_calc(&s->fft, x);
/* post rotation */
for(i=0;i<n4;i++) {
re = x[i].re;
im = x[i].im;
CMUL(re1, im1, re, im, -tsin[i], -tcos[i]);
out[2*i] = im1;
out[n2-1-2*i] = re1;
}
}

void mdct_end(MDCTContext *s)
{
av_freep(&s->tcos);
av_freep(&s->tsin);
fft_end(&s->fft);
}

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