mirror of
https://git.ffmpeg.org/ffmpeg.git
synced 2024-12-15 11:44:49 +00:00
242 lines
7.6 KiB
C
242 lines
7.6 KiB
C
/*
|
|
* Common code between the AC-3 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 the AC-3 encoder and decoder.
|
|
*/
|
|
|
|
#include "avcodec.h"
|
|
#include "ac3.h"
|
|
#include "bitstream.h"
|
|
|
|
static uint8_t band_start_tab[51];
|
|
static uint8_t bin_to_band_tab[253];
|
|
|
|
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);
|
|
}
|
|
}
|
|
|
|
void ff_ac3_bit_alloc_calc_psd(int8_t *exp, int start, int end, int16_t *psd,
|
|
int16_t *band_psd)
|
|
{
|
|
int bin, i, j, k, end1, v;
|
|
|
|
/* exponent mapping to PSD */
|
|
for(bin=start;bin<end;bin++) {
|
|
psd[bin]=(3072 - (exp[bin] << 7));
|
|
}
|
|
|
|
/* PSD integration */
|
|
j=start;
|
|
k=bin_to_band_tab[start];
|
|
do {
|
|
v=psd[j];
|
|
j++;
|
|
end1 = FFMIN(band_start_tab[k+1], end);
|
|
for(i=j;i<end1;i++) {
|
|
/* logadd */
|
|
int adr = FFMIN(FFABS(v - psd[j]) >> 1, 255);
|
|
v = FFMAX(v, psd[j]) + ff_ac3_log_add_tab[adr];
|
|
j++;
|
|
}
|
|
band_psd[k]=v;
|
|
k++;
|
|
} while (end > band_start_tab[k]);
|
|
}
|
|
|
|
void ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *band_psd,
|
|
int start, int end, int fast_gain, int is_lfe,
|
|
int dba_mode, int dba_nsegs, uint8_t *dba_offsets,
|
|
uint8_t *dba_lengths, uint8_t *dba_values,
|
|
int16_t *mask)
|
|
{
|
|
int16_t excite[50]; /* excitation */
|
|
int bin, k;
|
|
int bndstrt, bndend, begin, end1, tmp;
|
|
int lowcomp, fastleak, slowleak;
|
|
|
|
/* excitation function */
|
|
bndstrt = bin_to_band_tab[start];
|
|
bndend = bin_to_band_tab[end-1] + 1;
|
|
|
|
if (bndstrt == 0) {
|
|
lowcomp = 0;
|
|
lowcomp = calc_lowcomp1(lowcomp, band_psd[0], band_psd[1], 384);
|
|
excite[0] = band_psd[0] - fast_gain - lowcomp;
|
|
lowcomp = calc_lowcomp1(lowcomp, band_psd[1], band_psd[2], 384);
|
|
excite[1] = band_psd[1] - fast_gain - lowcomp;
|
|
begin = 7;
|
|
for (bin = 2; bin < 7; bin++) {
|
|
if (!(is_lfe && bin == 6))
|
|
lowcomp = calc_lowcomp1(lowcomp, band_psd[bin], band_psd[bin+1], 384);
|
|
fastleak = band_psd[bin] - fast_gain;
|
|
slowleak = band_psd[bin] - s->slow_gain;
|
|
excite[bin] = fastleak - lowcomp;
|
|
if (!(is_lfe && bin == 6)) {
|
|
if (band_psd[bin] <= band_psd[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, band_psd[bin], band_psd[bin+1], bin);
|
|
|
|
fastleak = FFMAX(fastleak - s->fast_decay, band_psd[bin] - fast_gain);
|
|
slowleak = FFMAX(slowleak - s->slow_decay, band_psd[bin] - s->slow_gain);
|
|
excite[bin] = FFMAX(fastleak - lowcomp, slowleak);
|
|
}
|
|
begin = 22;
|
|
} else {
|
|
/* coupling channel */
|
|
begin = bndstrt;
|
|
|
|
fastleak = (s->cpl_fast_leak << 8) + 768;
|
|
slowleak = (s->cpl_slow_leak << 8) + 768;
|
|
}
|
|
|
|
for (bin = begin; bin < bndend; bin++) {
|
|
fastleak = FFMAX(fastleak - s->fast_decay, band_psd[bin] - fast_gain);
|
|
slowleak = FFMAX(slowleak - s->slow_decay, band_psd[bin] - s->slow_gain);
|
|
excite[bin] = FFMAX(fastleak, slowleak);
|
|
}
|
|
|
|
/* compute masking curve */
|
|
|
|
for (bin = bndstrt; bin < bndend; bin++) {
|
|
tmp = s->db_per_bit - band_psd[bin];
|
|
if (tmp > 0) {
|
|
excite[bin] += tmp >> 2;
|
|
}
|
|
mask[bin] = FFMAX(ff_ac3_hearing_threshold_tab[bin >> s->sr_shift][s->sr_code], excite[bin]);
|
|
}
|
|
|
|
/* delta bit allocation */
|
|
|
|
if (dba_mode == DBA_REUSE || dba_mode == DBA_NEW) {
|
|
int band, seg, delta;
|
|
band = 0;
|
|
for (seg = 0; seg < FFMIN(8, dba_nsegs); seg++) {
|
|
band = FFMIN(49, band + dba_offsets[seg]);
|
|
if (dba_values[seg] >= 4) {
|
|
delta = (dba_values[seg] - 3) << 7;
|
|
} else {
|
|
delta = (dba_values[seg] - 4) << 7;
|
|
}
|
|
for (k = 0; k < dba_lengths[seg]; k++) {
|
|
mask[band] += delta;
|
|
band++;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
void ff_ac3_bit_alloc_calc_bap(int16_t *mask, int16_t *psd, int start, int end,
|
|
int snr_offset, int floor,
|
|
const uint8_t *bap_tab, uint8_t *bap)
|
|
{
|
|
int i, j, k, end1, v, address;
|
|
|
|
/* special case, if snr offset is -960, set all bap's to zero */
|
|
if(snr_offset == -960) {
|
|
memset(bap, 0, 256);
|
|
return;
|
|
}
|
|
|
|
i = start;
|
|
j = bin_to_band_tab[start];
|
|
do {
|
|
v = (FFMAX(mask[j] - snr_offset - floor, 0) & 0x1FE0) + floor;
|
|
end1 = FFMIN(band_start_tab[j] + ff_ac3_critical_band_size_tab[j], end);
|
|
for (k = i; k < end1; k++) {
|
|
address = av_clip((psd[i] - v) >> 5, 0, 63);
|
|
bap[i] = bap_tab[address];
|
|
i++;
|
|
}
|
|
} while (end > band_start_tab[j++]);
|
|
}
|
|
|
|
/* AC-3 bit allocation. The algorithm is the one described in the AC-3
|
|
spec. */
|
|
void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap,
|
|
int8_t *exp, int start, int end,
|
|
int snr_offset, int fast_gain, int is_lfe,
|
|
int dba_mode, int dba_nsegs,
|
|
uint8_t *dba_offsets, uint8_t *dba_lengths,
|
|
uint8_t *dba_values)
|
|
{
|
|
int16_t psd[256]; /* scaled exponents */
|
|
int16_t band_psd[50]; /* interpolated exponents */
|
|
int16_t mask[50]; /* masking value */
|
|
|
|
ff_ac3_bit_alloc_calc_psd(exp, start, end, psd, band_psd);
|
|
|
|
ff_ac3_bit_alloc_calc_mask(s, band_psd, start, end, fast_gain, is_lfe,
|
|
dba_mode, dba_nsegs, dba_offsets, dba_lengths, dba_values,
|
|
mask);
|
|
|
|
ff_ac3_bit_alloc_calc_bap(mask, psd, start, end, snr_offset, s->floor,
|
|
ff_ac3_bap_tab, bap);
|
|
}
|
|
|
|
/**
|
|
* Initializes some tables.
|
|
* note: This function must remain thread safe because it is called by the
|
|
* AVParser init code.
|
|
*/
|
|
av_cold 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++) {
|
|
band_start_tab[i] = l;
|
|
v = ff_ac3_critical_band_size_tab[i];
|
|
for(j=0;j<v;j++) bin_to_band_tab[k++]=i;
|
|
l += v;
|
|
}
|
|
band_start_tab[50] = l;
|
|
}
|