ref: 5a036511227b01a6957fe8e42016b5552ac9f7a6
dir: /libfaad/mdct.c/
/*
** FAAD2 - Freeware Advanced Audio (AAC) Decoder including SBR decoding
** Copyright (C) 2003-2005 M. Bakker, Nero 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.
**
** The "appropriate copyright message" mentioned in section 2c of the GPLv2
** must read: "Code from FAAD2 is copyright (c) Nero AG, www.nero.com"
**
** Commercial non-GPL licensing of this software is possible.
** For more info contact Nero AG through [email protected].
**
** $Id: mdct.c,v 1.47 2007/11/01 12:33:31 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"
#include "mdct_tab.h"
mdct_info *faad_mdct_init(uint16_t N)
{
mdct_info *mdct = (mdct_info*)faad_malloc(sizeof(mdct_info));
assert(N % 8 == 0);
mdct->N = N;
/* NOTE: For "small framelengths" in FIXED_POINT the coefficients need to be
* scaled by sqrt("(nearest power of 2) > N" / N) */
/* 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)); */
/* scale is 1 for fixed point, sqrt(N) for floating point */
switch (N)
{
case 2048: mdct->sincos = (complex_t*)mdct_tab_2048; break;
case 256: mdct->sincos = (complex_t*)mdct_tab_256; break;
#ifdef LD_DEC
case 1024: mdct->sincos = (complex_t*)mdct_tab_1024; break;
#endif
#ifdef ALLOW_SMALL_FRAMELENGTH
case 1920: mdct->sincos = (complex_t*)mdct_tab_1920; break;
case 240: mdct->sincos = (complex_t*)mdct_tab_240; break;
#ifdef LD_DEC
case 960: mdct->sincos = (complex_t*)mdct_tab_960; break;
#endif
#endif
#ifdef SSR_DEC
case 512: mdct->sincos = (complex_t*)mdct_tab_512; break;
case 64: mdct->sincos = (complex_t*)mdct_tab_64; break;
#endif
}
/* initialise fft */
mdct->cfft = cffti(N/4);
#ifdef PROFILE
mdct->cycles = 0;
mdct->fft_cycles = 0;
#endif
return mdct;
}
void faad_mdct_end(mdct_info *mdct)
{
if (mdct != NULL)
{
#ifdef PROFILE
printf("MDCT[%.4d]: %I64d cycles\n", mdct->N, mdct->cycles);
printf("CFFT[%.4d]: %I64d cycles\n", mdct->N/4, mdct->fft_cycles);
#endif
cfftu(mdct->cfft);
faad_free(mdct);
}
}
void faad_imdct(mdct_info *mdct, real_t *X_in, real_t *X_out)
{
uint16_t k;
complex_t x;
#ifdef ALLOW_SMALL_FRAMELENGTH
#ifdef FIXED_POINT
real_t scale, b_scale = 0;
#endif
#endif
ALIGN 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;
#ifdef PROFILE
int64_t count1, count2 = faad_get_ts();
#endif
#ifdef ALLOW_SMALL_FRAMELENGTH
#ifdef FIXED_POINT
/* detect non-power of 2 */
if (N & (N-1))
{
/* adjust scale for non-power of 2 MDCT */
/* 2048/1920 */
b_scale = 1;
scale = COEF_CONST(1.0666666666666667);
}
#endif
#endif
/* 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]));
}
#ifdef PROFILE
count1 = faad_get_ts();
#endif
/* complex IFFT, any non-scaling FFT can be used here */
cfftb(mdct->cfft, Z1);
#ifdef PROFILE
count1 = faad_get_ts() - count1;
#endif
/* 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 ALLOW_SMALL_FRAMELENGTH
#ifdef FIXED_POINT
/* non-power of 2 MDCT scaling */
if (b_scale)
{
RE(Z1[k]) = MUL_C(RE(Z1[k]), scale);
IM(Z1[k]) = MUL_C(IM(Z1[k]), scale);
}
#endif
#endif
}
/* reordering */
for (k = 0; k < N8; k+=2)
{
X_out[ 2*k] = IM(Z1[N8 + k]);
X_out[ 2 + 2*k] = IM(Z1[N8 + 1 + k]);
X_out[ 1 + 2*k] = -RE(Z1[N8 - 1 - k]);
X_out[ 3 + 2*k] = -RE(Z1[N8 - 2 - k]);
X_out[N4 + 2*k] = RE(Z1[ k]);
X_out[N4 + + 2 + 2*k] = RE(Z1[ 1 + k]);
X_out[N4 + 1 + 2*k] = -IM(Z1[N4 - 1 - k]);
X_out[N4 + 3 + 2*k] = -IM(Z1[N4 - 2 - k]);
X_out[N2 + 2*k] = RE(Z1[N8 + k]);
X_out[N2 + + 2 + 2*k] = RE(Z1[N8 + 1 + k]);
X_out[N2 + 1 + 2*k] = -IM(Z1[N8 - 1 - k]);
X_out[N2 + 3 + 2*k] = -IM(Z1[N8 - 2 - k]);
X_out[N2 + N4 + 2*k] = -IM(Z1[ k]);
X_out[N2 + N4 + 2 + 2*k] = -IM(Z1[ 1 + k]);
X_out[N2 + N4 + 1 + 2*k] = RE(Z1[N4 - 1 - k]);
X_out[N2 + N4 + 3 + 2*k] = RE(Z1[N4 - 2 - k]);
}
#ifdef PROFILE
count2 = faad_get_ts() - count2;
mdct->fft_cycles += count1;
mdct->cycles += (count2 - count1);
#endif
}
#ifdef LTP_DEC
void faad_mdct(mdct_info *mdct, real_t *X_in, real_t *X_out)
{
uint16_t k;
complex_t x;
ALIGN 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
#ifdef ALLOW_SMALL_FRAMELENGTH
#ifdef FIXED_POINT
/* detect non-power of 2 */
if (N & (N-1))
{
/* adjust scale for non-power of 2 MDCT */
/* *= sqrt(2048/1920) */
scale = MUL_C(scale, COEF_CONST(1.0327955589886444));
}
#endif
#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