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/*
* WMA compatible decoder
* Copyright (c) 2002 The FFmpeg Project.
*
* 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 "wmafixed.h"
#include "mdct.h"
fixed32 tcos0[1024], tsin0[1024]; //these are the sin and cos rotations used by the MDCT
uint16_t revtab0[1024];
/**
* init MDCT or IMDCT computation.
*/
int ff_mdct_init(MDCTContext *s, int nbits, int inverse)
{
int n;
// fixed32 alpha;
memset(s, 0, sizeof(*s));
n = 1 << nbits; //nbits ranges from 12 to 8 inclusive
s->nbits = nbits;
s->n = n;
(&s->fft)->nbits = nbits-2;
(&s->fft)->inverse = inverse;
return 0;
}
/**
* Compute inverse MDCT of size N = 2^nbits
* @param output N samples
* @param input N/2 samples
* @param tmp N/2 samples
*/
void ff_imdct_calc(MDCTContext *s,
fixed32 *output,
fixed32 *input)
{
int k, n8, n4, n2, n, j,scale;
const fixed32 *in1, *in2;
FFTComplex *z1 = (FFTComplex *)output;
FFTComplex *z2 = (FFTComplex *)input;
int revtabshift = 12 - s->nbits;
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++)
{
int kshift = k<<revtabshift;
j=revtab0[kshift];
CMUL(&z1[j].re, &z1[j].im, *in2, *in1, tcos0[kshift], tsin0[kshift]);
in1 += 2;
in2 -= 2;
}
scale = fft_calc_unscaled(&s->fft, z1);
/* post rotation + reordering */
for(k = 0; k < n4; k++)
{
int kshift = k<<revtabshift;
CMUL(&z2[k].re, &z2[k].im, (z1[k].re), (z1[k].im), tcos0[kshift], tsin0[kshift]);
}
for(k = 0; k < n8; k++)
{
fixed32 r1,r2,r3,r4,r1n,r2n,r3n;
r1 = z2[n8 + k].im;
r1n = r1 * -1;
r2 = z2[n8-1-k].re;
r2n = r2 * -1;
r3 = z2[k+n8].re;
r3n = r3 * -1;
r4 = z2[n8-k-1].im;
output[2*k] = r1n;
output[n2-1-2*k] = r1;
output[2*k+1] = r2;
output[n2-1-2*k-1] = r2n;
output[n2 + 2*k]= r3n;
output[n-1- 2*k]= r3n;
output[n2 + 2*k+1]= r4;
output[n-2 - 2 * k] = r4;
}
}
int mdct_init_global(void)
{
int i,j,m;
/* init the MDCT bit reverse table here rather then in fft_init */
for(i=0;i<1024;i++) /*hard coded to a 2048 bit rotation*/
{ /*smaller sizes can reuse the largest*/
m=0;
for(j=0;j<10;j++)
{
m |= ((i >> j) & 1) << (10-j-1);
}
revtab0[i]=m;
}
for(i=0;i<1024;i++)
{
//fixed32 pi2 = fixmul32(0x20000, M_PI_F);
fixed32 ip = itofix32(i) + 0x2000;
ip = ip >> 12;
//ip = fixdiv32(ip,itofix32(n)); // PJJ optimize
//alpha = fixmul32(TWO_M_PI_F, ip);
//s->tcos[i] = -fixcos32(alpha); //alpha between 0 and pi/2
//s->tsin[i] = -fixsin32(alpha);
//I can't remember why this works, but it seems to agree for ~24 bits, maybe more!
tsin0[i] = - fsincos(ip<<16, &(tcos0[i]));
tcos0[i] *=-1;
}
fft_init_global();
return 0;
}
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