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/*
* Common code between AC3 encoder and decoder
* Copyright (c) 2000 Fabrice Bellard.
*
* This file is part of FFmpeg.
*
* FFmpeg 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.
*
* FFmpeg 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 FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
/**
* @file ac3.c
* Common code between AC3 encoder and decoder.
*/
#include "avcodec.h"
#include "ac3.h"
#include "ac3tab.h"
static inline int calc_lowcomp1(int a, int b0, int b1, int c)
{
if ((b0 + 256) == b1) {
a = c;
} else if (b0 > b1) {
a = FFMAX(a - 64, 0);
}
return a;
}
static inline int calc_lowcomp(int a, int b0, int b1, int bin)
{
if (bin < 7) {
return calc_lowcomp1(a, b0, b1, 384);
} else if (bin < 20) {
return calc_lowcomp1(a, b0, b1, 320);
} else {
return FFMAX(a - 128, 0);
}
}
/* AC3 bit allocation. The algorithm is the one described in the AC3
spec. */
void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap,
int8_t *exp, int start, int end,
int snroffset, int fgain, int is_lfe,
int deltbae,int deltnseg,
uint8_t *deltoffst, uint8_t *deltlen, uint8_t *deltba)
{
int bin,i,j,k,end1,v,bndstrt,bndend,lowcomp,begin;
int fastleak,slowleak,address,tmp;
int16_t psd[256]; /* scaled exponents */
int16_t bndpsd[50]; /* interpolated exponents */
int16_t excite[50]; /* excitation */
int16_t mask[50]; /* masking value */
/* exponent mapping to PSD */
for(bin=start;bin<end;bin++) {
psd[bin]=(3072 - (exp[bin] << 7));
}
/* PSD integration */
j=start;
k=masktab[start];
do {
v=psd[j];
j++;
end1 = FFMIN(bndtab[k+1], end);
for(i=j;i<end1;i++) {
/* logadd */
int adr = FFMIN(FFABS(v - psd[j]) >> 1, 255);
v = FFMAX(v, psd[j]) + latab[adr];
j++;
}
bndpsd[k]=v;
k++;
} while (end > bndtab[k]);
/* excitation function */
bndstrt = masktab[start];
bndend = masktab[end-1] + 1;
if (bndstrt == 0) {
lowcomp = 0;
lowcomp = calc_lowcomp1(lowcomp, bndpsd[0], bndpsd[1], 384);
excite[0] = bndpsd[0] - fgain - lowcomp;
lowcomp = calc_lowcomp1(lowcomp, bndpsd[1], bndpsd[2], 384);
excite[1] = bndpsd[1] - fgain - lowcomp;
begin = 7;
for (bin = 2; bin < 7; bin++) {
if (!(is_lfe && bin == 6))
lowcomp = calc_lowcomp1(lowcomp, bndpsd[bin], bndpsd[bin+1], 384);
fastleak = bndpsd[bin] - fgain;
slowleak = bndpsd[bin] - s->sgain;
excite[bin] = fastleak - lowcomp;
if (!(is_lfe && bin == 6)) {
if (bndpsd[bin] <= bndpsd[bin+1]) {
begin = bin + 1;
break;
}
}
}
end1=bndend;
if (end1 > 22) end1=22;
for (bin = begin; bin < end1; bin++) {
if (!(is_lfe && bin == 6))
lowcomp = calc_lowcomp(lowcomp, bndpsd[bin], bndpsd[bin+1], bin);
fastleak = FFMAX(fastleak - s->fdecay, bndpsd[bin] - fgain);
slowleak = FFMAX(slowleak - s->sdecay, bndpsd[bin] - s->sgain);
excite[bin] = FFMAX(fastleak - lowcomp, slowleak);
}
begin = 22;
} else {
/* coupling channel */
begin = bndstrt;
fastleak = (s->cplfleak << 8) + 768;
slowleak = (s->cplsleak << 8) + 768;
}
for (bin = begin; bin < bndend; bin++) {
fastleak = FFMAX(fastleak - s->fdecay, bndpsd[bin] - fgain);
slowleak = FFMAX(slowleak - s->sdecay, bndpsd[bin] - s->sgain);
excite[bin] = FFMAX(fastleak, slowleak);
}
/* compute masking curve */
for (bin = bndstrt; bin < bndend; bin++) {
tmp = s->dbknee - bndpsd[bin];
if (tmp > 0) {
excite[bin] += tmp >> 2;
}
mask[bin] = FFMAX(hth[bin >> s->halfratecod][s->fscod], excite[bin]);
}
/* delta bit allocation */
if (deltbae == 0 || deltbae == 1) {
int band, seg, delta;
band = 0;
for (seg = 0; seg < deltnseg; seg++) {
band += deltoffst[seg];
if (deltba[seg] >= 4) {
delta = (deltba[seg] - 3) << 7;
} else {
delta = (deltba[seg] - 4) << 7;
}
for (k = 0; k < deltlen[seg]; k++) {
mask[band] += delta;
band++;
}
}
}
/* compute bit allocation */
i = start;
j = masktab[start];
do {
v = (FFMAX(mask[j] - snroffset - s->floor, 0) & 0x1FE0) + s->floor;
end1 = FFMIN(bndtab[j] + bndsz[j], end);
for (k = i; k < end1; k++) {
address = av_clip((psd[i] - v) >> 5, 0, 63);
bap[i] = baptab[address];
i++;
}
} while (end > bndtab[j++]);
}
void ac3_common_init(void)
{
int i, j, k, l, v;
/* compute bndtab and masktab from bandsz */
k = 0;
l = 0;
for(i=0;i<50;i++) {
bndtab[i] = l;
v = bndsz[i];
for(j=0;j<v;j++) masktab[k++]=i;
l += v;
}
bndtab[50] = l;
}
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