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/*
* TwoLAME: an optimized MPEG Audio Layer Two encoder
*
* Copyright (C) 2001-2004 Michael Cheng
* Copyright (C) 2004-2006 The TwoLAME 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 2.1 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
*
* $Id$
*
*/
#include <stdio.h>
#include <string.h>
#include <math.h>
#include "twolame.h"
#include "common.h"
#include "mem.h"
#include "bitbuffer.h"
#include "enwindow.h"
#include "subband.h"
static void create_dct_matrix(FLOAT filter[16][32])
{
register int i, k;
for (i = 0; i < 16; i++)
for (k = 0; k < 32; k++) {
if ((filter[i][k] = 1e9 * cos((FLOAT) ((2 * i + 1) * k * PI64))) >= 0)
modf(filter[i][k] + 0.5, &filter[i][k]);
else
modf(filter[i][k] - 0.5, &filter[i][k]);
filter[i][k] *= 1e-9;
}
}
int init_subband(subband_mem * smem)
{
register int i, j;
smem->off[0] = 0;
smem->off[1] = 0;
smem->half[0] = 0;
smem->half[1] = 0;
for (i = 0; i < 2; i++)
for (j = 0; j < 512; j++)
smem->x[i][j] = 0;
create_dct_matrix(smem->m);
return 0;
}
void window_filter_subband(subband_mem * smem, short *pBuffer, int ch, FLOAT s[SBLIMIT])
{
register int i, j;
int pa, pb, pc, pd, pe, pf, pg, ph;
FLOAT t;
FLOAT *dp, *dp2;
const FLOAT *pEnw;
FLOAT y[64];
FLOAT yprime[32];
dp = smem->x[ch] + smem->off[ch] + smem->half[ch] * 256;
/* replace 32 oldest samples with 32 new samples */
for (i = 0; i < 32; i++)
dp[(31 - i) * 8] = (FLOAT) pBuffer[i] / SCALE;
// looks like "school example" but does faster ...
dp = (smem->x[ch] + smem->half[ch] * 256);
pa = smem->off[ch];
pb = (pa + 1) % 8;
pc = (pa + 2) % 8;
pd = (pa + 3) % 8;
pe = (pa + 4) % 8;
pf = (pa + 5) % 8;
pg = (pa + 6) % 8;
ph = (pa + 7) % 8;
for (i = 0; i < 32; i++) {
dp2 = dp + i * 8;
pEnw = enwindow + i;
t = dp2[pa] * pEnw[0];
t += dp2[pb] * pEnw[64];
t += dp2[pc] * pEnw[128];
t += dp2[pd] * pEnw[192];
t += dp2[pe] * pEnw[256];
t += dp2[pf] * pEnw[320];
t += dp2[pg] * pEnw[384];
t += dp2[ph] * pEnw[448];
y[i] = t;
}
yprime[0] = y[16]; // Michael Chen's dct filter
dp = smem->half[ch] ? smem->x[ch] : (smem->x[ch] + 256);
pa = smem->half[ch] ? (smem->off[ch] + 1) & 7 : smem->off[ch];
pb = (pa + 1) % 8;
pc = (pa + 2) % 8;
pd = (pa + 3) % 8;
pe = (pa + 4) % 8;
pf = (pa + 5) % 8;
pg = (pa + 6) % 8;
ph = (pa + 7) % 8;
for (i = 0; i < 32; i++) {
dp2 = dp + i * 8;
pEnw = enwindow + i + 32;
t = dp2[pa] * pEnw[0];
t += dp2[pb] * pEnw[64];
t += dp2[pc] * pEnw[128];
t += dp2[pd] * pEnw[192];
t += dp2[pe] * pEnw[256];
t += dp2[pf] * pEnw[320];
t += dp2[pg] * pEnw[384];
t += dp2[ph] * pEnw[448];
y[i + 32] = t;
// 1st pass on Michael Chen's dct filter
if (i > 0 && i < 17)
yprime[i] = y[i + 16] + y[16 - i];
}
// 2nd pass on Michael Chen's dct filter
for (i = 17; i < 32; i++)
yprime[i] = y[i + 16] - y[80 - i];
for (i = 15; i >= 0; i--) {
register FLOAT s0 = 0.0, s1 = 0.0;
register FLOAT *mp = smem->m[i];
register FLOAT *xinp = yprime;
for (j = 0; j < 8; j++) {
s0 += *mp++ * *xinp++;
s1 += *mp++ * *xinp++;
s0 += *mp++ * *xinp++;
s1 += *mp++ * *xinp++;
}
s[i] = s0 + s1;
s[31 - i] = s0 - s1;
}
smem->half[ch] = (smem->half[ch] + 1) & 1;
if (smem->half[ch] == 1)
smem->off[ch] = (smem->off[ch] + 7) & 7;
}
// vim:ts=4:sw=4:nowrap:
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