ref: 4f9a9087f16b92662389be3dc0589629359ac8a4
dir: /libfaad/mdct.c/
/*
** FAAD - Freeware Advanced Audio Decoder
** Copyright (C) 2002 M. Bakker
**
** 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.
**
** $Id: mdct.c,v 1.7 2002/04/07 21:26:04 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.
* Thanks to the FFTW library this (I)MDCT can now be used for any data
* size n, where n is divisible by 8.
*
*/
#include "common.h"
#include <stdlib.h>
#include <assert.h>
/* uses fftw (http://www.fftw.org) for very fast arbitrary-n FFT and IFFT */
#include <fftw.h>
#include "mdct.h"
void faad_mdct_init(mdct_info *mdct, uint16_t N)
{
uint16_t k;
assert(N % 8 == 0);
mdct->N = N;
mdct->sincos = (faad_sincos*)malloc(N/4*sizeof(faad_sincos));
mdct->Z1 = (fftw_complex*)malloc(N/4*sizeof(faad_complex));
mdct->Z2 = (fftw_complex*)malloc(N/4*sizeof(faad_complex));
for (k = 0; k < N/4; k++)
{
real_t angle = 2.0 * M_PI * (k + 1.0/8.0)/(real_t)N;
mdct->sincos[k].sin = -sin(angle);
mdct->sincos[k].cos = -cos(angle);
}
mdct->plan_backward = fftw_create_plan(N/4, FFTW_BACKWARD, FFTW_ESTIMATE);
#ifdef LTP_DEC
mdct->plan_forward = fftw_create_plan(N/4, FFTW_FORWARD, FFTW_ESTIMATE);
#endif
}
void faad_mdct_end(mdct_info *mdct)
{
fftw_destroy_plan(mdct->plan_backward);
#ifdef LTP_DEC
fftw_destroy_plan(mdct->plan_forward);
#endif
if (mdct->Z2) free(mdct->Z2);
if (mdct->Z1) free(mdct->Z1);
if (mdct->sincos) free(mdct->sincos);
}
void faad_imdct(mdct_info *mdct, real_t *X_in, real_t *X_out)
{
uint16_t k;
fftw_complex *Z1 = mdct->Z1;
fftw_complex *Z2 = mdct->Z2;
faad_sincos *sincos = mdct->sincos;
uint16_t N = mdct->N;
uint16_t N2 = N >> 1;
uint16_t N4 = N >> 2;
uint16_t N8 = N >> 3;
real_t fac = 2.0/(real_t)N;
/* pre-IFFT complex multiplication */
for (k = 0; k < N4; k++)
{
uint16_t n = k << 1;
real_t x0 = X_in[ n];
real_t x1 = X_in[N2 - 1 - n];
Z1[k].re = x1 * sincos[k].cos - x0 * sincos[k].sin;
Z1[k].im = x0 * sincos[k].cos + x1 * sincos[k].sin;
}
/* complex IFFT */
fftw_one(mdct->plan_backward, Z1, Z2);
/* post-IFFT complex multiplication */
for (k = 0; k < N4; k++)
{
real_t zr = Z2[k].re;
real_t zi = Z2[k].im;
Z2[k].re = fac * (zr * sincos[k].cos - zi * sincos[k].sin);
Z2[k].im = fac * (zi * sincos[k].cos + zr * sincos[k].sin);
}
/* reordering */
for (k = 0; k < N8; k++)
{
uint16_t n = k << 1;
X_out[ n] = -Z2[N8 + k].im;
X_out[ 1 + n] = Z2[N8 - 1 - k].re;
X_out[N4 + n] = -Z2[ k].re;
X_out[N4 + 1 + n] = Z2[N4 - 1 - k].im;
X_out[N2 + n] = -Z2[N8 + k].re;
X_out[N2 + 1 + n] = Z2[N8 - 1 - k].im;
X_out[N2 + N4 + n] = Z2[ k].im;
X_out[N2 + N4 + 1 + n] = -Z2[N4 - 1 - k].re;
}
}
#ifdef LTP_DEC
void faad_mdct(mdct_info *mdct, real_t *X_in, real_t *X_out)
{
uint16_t k;
fftw_complex *Z1 = mdct->Z1;
fftw_complex *Z2 = mdct->Z2;
faad_sincos *sincos = mdct->sincos;
uint16_t N = mdct->N;
uint16_t N2 = N >> 1;
uint16_t N4 = N >> 2;
uint16_t N8 = N >> 3;
/* pre-FFT complex multiplication */
for (k = 0; k < N8; k++)
{
uint16_t n = k << 1;
real_t zr = X_in[N - N4 - 1 - n] + X_in[N - N4 + n];
real_t zi = X_in[ N4 + n] - X_in[ N4 - 1 - n];
Z1[k ].re = -zr * sincos[k ].cos - zi * sincos[k ].sin;
Z1[k ].im = -zi * sincos[k ].cos + zr * sincos[k ].sin;
zr = X_in[ N2 - 1 - n] - X_in[ n];
zi = X_in[ N2 + n] + X_in[N - 1 - n];
Z1[k + N8].re = -zr * sincos[k + N8].cos - zi * sincos[k + N8].sin;
Z1[k + N8].im = -zi * sincos[k + N8].cos + zr * sincos[k + N8].sin;
}
/* complex FFT */
fftw_one(mdct->plan_forward, Z1, Z2);
/* post-FFT complex multiplication */
for (k = 0; k < N4; k++)
{
uint16_t n = k << 1;
real_t zr = 2.0 * (Z2[k].re * sincos[k].cos + Z2[k].im * sincos[k].sin);
real_t zi = 2.0 * (Z2[k].im * sincos[k].cos - Z2[k].re * sincos[k].sin);
X_out[ n] = -zr;
X_out[N2 - 1 - n] = zi;
X_out[N2 + n] = -zi;
X_out[N - 1 - n] = zr;
}
}
#endif