ref: dbdd0f664f37a11b8e06e07905d12527509e2723
dir: /libfaad/mdct.c/
/*
** FAAD2 - Freeware Advanced Audio (AAC) Decoder including SBR decoding
** Copyright (C) 2003 M. Bakker, Ahead Software AG, http://www.nero.com
**
** This program is free software; you can redistribute it and/or modify
** it under the terms of the GNU General Public License as published by
** the Free Software Foundation; either version 2 of the License, or
** (at your option) any later version.
**
** This program 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 General Public License for more details.
**
** You should have received a copy of the GNU General Public License
** along with this program; if not, write to the Free Software
** Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
**
** Any non-GPL usage of this software or parts of this software is strictly
** forbidden.
**
** Commercial non-GPL licensing of this software is possible.
** For more info contact Ahead Software through Mpeg4AAClicense@nero.com.
**
** $Id: mdct.c,v 1.34 2003/11/12 20:47:58 menno Exp $
**/
/*
* Fast (I)MDCT Implementation using (I)FFT ((Inverse) Fast Fourier Transform)
* and consists of three steps: pre-(I)FFT complex multiplication, complex
* (I)FFT, post-(I)FFT complex multiplication,
*
* As described in:
* P. Duhamel, Y. Mahieux, and J.P. Petit, "A Fast Algorithm for the
* Implementation of Filter Banks Based on 'Time Domain Aliasing
* Cancellation�," IEEE Proc. on ICASSP�91, 1991, pp. 2209-2212.
*
*
* As of April 6th 2002 completely rewritten.
* This (I)MDCT can now be used for any data size n, where n is divisible by 8.
*
*/
#include "common.h"
#include "structs.h"
#include <stdlib.h>
#ifdef _WIN32_WCE
#define assert(x)
#else
#include <assert.h>
#endif
#include "cfft.h"
#include "mdct.h"
/* const_tab[]:
0: sqrt(2 / N)
1: cos(2 * PI / N)
2: sin(2 * PI / N)
3: cos(2 * PI * (1/8) / N)
4: sin(2 * PI * (1/8) / N)
*/
#ifdef FIXED_POINT
real_t const_tab[][5] =
{
{ /* 2048 */
COEF_CONST(1),
FRAC_CONST(0.99999529380957619),
FRAC_CONST(0.0030679567629659761),
FRAC_CONST(0.99999992646571789),
FRAC_CONST(0.00038349518757139556)
}, { /* 1920 */
COEF_CONST(/* sqrt(1024/960) */ 1.0327955589886444),
FRAC_CONST(0.99999464540169647),
FRAC_CONST(0.0032724865065266251),
FRAC_CONST(0.99999991633432805),
FRAC_CONST(0.00040906153202803459)
}, { /* 1024 */
COEF_CONST(1),
FRAC_CONST(0.99998117528260111),
FRAC_CONST(0.0061358846491544753),
FRAC_CONST(0.99999970586288223),
FRAC_CONST(0.00076699031874270449)
}, { /* 960 */
COEF_CONST(/* sqrt(512/480) */ 1.0327955589886444),
FRAC_CONST(0.99997858166412923),
FRAC_CONST(0.0065449379673518581),
FRAC_CONST(0.99999966533732598),
FRAC_CONST(0.00081812299560725323)
}, { /* 256 */
COEF_CONST(1),
FRAC_CONST(0.99969881869620425),
FRAC_CONST(0.024541228522912288),
FRAC_CONST(0.99999529380957619),
FRAC_CONST(0.0030679567629659761)
}, { /* 240 */
COEF_CONST(/* sqrt(256/240) */ 1.0327955589886444),
FRAC_CONST(0.99965732497555726),
FRAC_CONST(0.026176948307873149),
FRAC_CONST(0.99999464540169647),
FRAC_CONST(0.0032724865065266251)
}
#ifdef SSR_DEC
,{ /* 512 */
COEF_CONST(1),
FRAC_CONST(0.9999247018391445),
FRAC_CONST(0.012271538285719925),
FRAC_CONST(0.99999882345170188),
FRAC_CONST(0.0015339801862847655)
}, { /* 64 */
COEF_CONST(1),
FRAC_CONST(0.99518472667219693),
FRAC_CONST(0.098017140329560604),
FRAC_CONST(0.9999247018391445),
FRAC_CONST(0.012271538285719925)
}
#endif
};
#endif
uint8_t map_N_to_idx(uint16_t N)
{
/* gives an index into const_tab above */
/* for normal AAC deocding (eg. no scalable profile) only */
/* index 0 and 4 will be used */
switch(N)
{
case 2048: return 0;
case 1920: return 1;
case 1024: return 2;
case 960: return 3;
case 256: return 4;
case 240: return 5;
#ifdef SSR_DEC
case 512: return 6;
case 64: return 7;
#endif
}
return 0;
}
mdct_info *faad_mdct_init(uint16_t N)
{
uint16_t k;
#ifdef FIXED_POINT
uint16_t N_idx;
real_t cangle, sangle, c, s, cold;
#endif
real_t scale;
mdct_info *mdct = (mdct_info*)malloc(sizeof(mdct_info));
assert(N % 8 == 0);
mdct->N = N;
mdct->sincos = (complex_t*)malloc(N/4*sizeof(complex_t));
#ifdef FIXED_POINT
N_idx = map_N_to_idx(N);
scale = const_tab[N_idx][0];
cangle = const_tab[N_idx][1];
sangle = const_tab[N_idx][2];
c = const_tab[N_idx][3];
s = const_tab[N_idx][4];
#else
scale = (real_t)sqrt(2.0 / (real_t)N);
#endif
/* (co)sine table build using recurrence relations */
/* this can also be done using static table lookup or */
/* some form of interpolation */
for (k = 0; k < N/4; k++)
{
#ifdef FIXED_POINT
RE(mdct->sincos[k]) = c; //MUL_C_C(c,scale);
IM(mdct->sincos[k]) = s; //MUL_C_C(s,scale);
cold = c;
c = MUL_F(c,cangle) - MUL_F(s,sangle);
s = MUL_F(s,cangle) + MUL_F(cold,sangle);
#else
/* no recurrence, just sines */
RE(mdct->sincos[k]) = scale*(real_t)(cos(2.0*M_PI*(k+1./8.) / (real_t)N));
IM(mdct->sincos[k]) = scale*(real_t)(sin(2.0*M_PI*(k+1./8.) / (real_t)N));
#endif
}
/* initialise fft */
mdct->cfft = cffti(N/4);
return mdct;
}
void faad_mdct_end(mdct_info *mdct)
{
if (mdct != NULL)
{
cfftu(mdct->cfft);
if (mdct->sincos) free(mdct->sincos);
free(mdct);
}
}
void faad_imdct(mdct_info *mdct, real_t *X_in, real_t *X_out)
{
uint16_t k;
complex_t x;
complex_t Z1[512];
complex_t *sincos = mdct->sincos;
uint16_t N = mdct->N;
uint16_t N2 = N >> 1;
uint16_t N4 = N >> 2;
uint16_t N8 = N >> 3;
/* pre-IFFT complex multiplication */
for (k = 0; k < N4; k++)
{
ComplexMult(&IM(Z1[k]), &RE(Z1[k]),
X_in[2*k], X_in[N2 - 1 - 2*k], RE(sincos[k]), IM(sincos[k]));
}
/* complex IFFT, any non-scaling FFT can be used here */
cfftb(mdct->cfft, Z1);
/* post-IFFT complex multiplication */
for (k = 0; k < N4; k++)
{
RE(x) = RE(Z1[k]);
IM(x) = IM(Z1[k]);
ComplexMult(&IM(Z1[k]), &RE(Z1[k]),
IM(x), RE(x), RE(sincos[k]), IM(sincos[k]));
#ifdef FIXED_POINT
#if (REAL_BITS == 16)
if (abs(RE(Z1[k])) > REAL_CONST(16383.5))
{
if (RE(Z1[k]) > 0) RE(Z1[k]) = REAL_CONST(32767.0);
else RE(Z1[k]) = REAL_CONST(-32767.0);
} else {
RE(Z1[k]) *= 2;
}
if (abs(IM(Z1[k])) > REAL_CONST(16383.5))
{
if (IM(Z1[k]) > 0) IM(Z1[k]) = REAL_CONST(32767.0);
else IM(Z1[k]) = REAL_CONST(-32767.0);
} else {
IM(Z1[k]) *= 2;
}
#endif
#endif
}
/* reordering */
for (k = 0; k < N8; k++)
{
X_out[ 2*k] = IM(Z1[N8 + k]);
X_out[ 1 + 2*k] = -RE(Z1[N8 - 1 - k]);
X_out[N4 + 2*k] = RE(Z1[ k]);
X_out[N4 + 1 + 2*k] = -IM(Z1[N4 - 1 - k]);
X_out[N2 + 2*k] = RE(Z1[N8 + k]);
X_out[N2 + 1 + 2*k] = -IM(Z1[N8 - 1 - k]);
X_out[N2 + N4 + 2*k] = -IM(Z1[ k]);
X_out[N2 + N4 + 1 + 2*k] = RE(Z1[N4 - 1 - k]);
}
}
#ifdef LTP_DEC
void faad_mdct(mdct_info *mdct, real_t *X_in, real_t *X_out)
{
uint16_t k;
complex_t x;
complex_t Z1[512];
complex_t *sincos = mdct->sincos;
uint16_t N = mdct->N;
uint16_t N2 = N >> 1;
uint16_t N4 = N >> 2;
uint16_t N8 = N >> 3;
#ifndef FIXED_POINT
real_t scale = REAL_CONST(N);
#else
real_t scale = REAL_CONST(4.0/N);
#endif
/* pre-FFT complex multiplication */
for (k = 0; k < N8; k++)
{
uint16_t n = k << 1;
RE(x) = X_in[N - N4 - 1 - n] + X_in[N - N4 + n];
IM(x) = X_in[ N4 + n] - X_in[ N4 - 1 - n];
ComplexMult(&RE(Z1[k]), &IM(Z1[k]),
RE(x), IM(x), RE(sincos[k]), IM(sincos[k]));
RE(Z1[k]) = MUL_R(RE(Z1[k]), scale);
IM(Z1[k]) = MUL_R(IM(Z1[k]), scale);
RE(x) = X_in[N2 - 1 - n] - X_in[ n];
IM(x) = X_in[N2 + n] + X_in[N - 1 - n];
ComplexMult(&RE(Z1[k + N8]), &IM(Z1[k + N8]),
RE(x), IM(x), RE(sincos[k + N8]), IM(sincos[k + N8]));
RE(Z1[k + N8]) = MUL_R(RE(Z1[k + N8]), scale);
IM(Z1[k + N8]) = MUL_R(IM(Z1[k + N8]), scale);
}
/* complex FFT, any non-scaling FFT can be used here */
cfftf(mdct->cfft, Z1);
/* post-FFT complex multiplication */
for (k = 0; k < N4; k++)
{
uint16_t n = k << 1;
ComplexMult(&RE(x), &IM(x),
RE(Z1[k]), IM(Z1[k]), RE(sincos[k]), IM(sincos[k]));
X_out[ n] = -RE(x);
X_out[N2 - 1 - n] = IM(x);
X_out[N2 + n] = -IM(x);
X_out[N - 1 - n] = RE(x);
}
}
#endif