mirror of https://github.com/FFmpeg/FFmpeg.git
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
281 lines
8.3 KiB
281 lines
8.3 KiB
/* |
|
* 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" |
|
#include "bitstream.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); |
|
} |
|
} |
|
|
|
void ff_ac3_bit_alloc_calc_psd(int8_t *exp, int start, int end, int16_t *psd, |
|
int16_t *bndpsd) |
|
{ |
|
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=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]); |
|
} |
|
|
|
void ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *bndpsd, |
|
int start, int end, int fgain, int is_lfe, |
|
int deltbae, int deltnseg, uint8_t *deltoffst, |
|
uint8_t *deltlen, uint8_t *deltba, |
|
int16_t *mask) |
|
{ |
|
int16_t excite[50]; /* excitation */ |
|
int bin, k; |
|
int bndstrt, bndend, begin, end1, tmp; |
|
int lowcomp, fastleak, slowleak; |
|
|
|
/* 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++; |
|
} |
|
} |
|
} |
|
} |
|
|
|
void ff_ac3_bit_alloc_calc_bap(int16_t *mask, int16_t *psd, int start, int end, |
|
int snroffset, int floor, uint8_t *bap) |
|
{ |
|
int i, j, k, end1, v, address; |
|
|
|
i = start; |
|
j = masktab[start]; |
|
do { |
|
v = (FFMAX(mask[j] - snroffset - floor, 0) & 0x1FE0) + 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++]); |
|
} |
|
|
|
/* 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) |
|
{ |
|
int16_t psd[256]; /* scaled exponents */ |
|
int16_t bndpsd[50]; /* interpolated exponents */ |
|
int16_t mask[50]; /* masking value */ |
|
|
|
ff_ac3_bit_alloc_calc_psd(exp, start, end, psd, bndpsd); |
|
|
|
ff_ac3_bit_alloc_calc_mask(s, bndpsd, start, end, fgain, is_lfe, |
|
deltbae, deltnseg, deltoffst, deltlen, deltba, |
|
mask); |
|
|
|
ff_ac3_bit_alloc_calc_bap(mask, psd, start, end, snroffset, s->floor, bap); |
|
} |
|
|
|
/** |
|
* Initializes some tables. |
|
* note: This function must remain thread safe because it is called by the |
|
* AVParser init code. |
|
*/ |
|
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; |
|
} |
|
|
|
int ff_ac3_parse_header(const uint8_t buf[7], AC3HeaderInfo *hdr) |
|
{ |
|
GetBitContext gbc; |
|
|
|
memset(hdr, 0, sizeof(*hdr)); |
|
|
|
init_get_bits(&gbc, buf, 54); |
|
|
|
hdr->sync_word = get_bits(&gbc, 16); |
|
if(hdr->sync_word != 0x0B77) |
|
return -1; |
|
|
|
/* read ahead to bsid to make sure this is AC-3, not E-AC-3 */ |
|
hdr->bsid = show_bits_long(&gbc, 29) & 0x1F; |
|
if(hdr->bsid > 10) |
|
return -2; |
|
|
|
hdr->crc1 = get_bits(&gbc, 16); |
|
hdr->fscod = get_bits(&gbc, 2); |
|
if(hdr->fscod == 3) |
|
return -3; |
|
|
|
hdr->frmsizecod = get_bits(&gbc, 6); |
|
if(hdr->frmsizecod > 37) |
|
return -4; |
|
|
|
skip_bits(&gbc, 5); // skip bsid, already got it |
|
|
|
hdr->bsmod = get_bits(&gbc, 3); |
|
hdr->acmod = get_bits(&gbc, 3); |
|
if((hdr->acmod & 1) && hdr->acmod != 1) { |
|
hdr->cmixlev = get_bits(&gbc, 2); |
|
} |
|
if(hdr->acmod & 4) { |
|
hdr->surmixlev = get_bits(&gbc, 2); |
|
} |
|
if(hdr->acmod == 2) { |
|
hdr->dsurmod = get_bits(&gbc, 2); |
|
} |
|
hdr->lfeon = get_bits1(&gbc); |
|
|
|
hdr->halfratecod = FFMAX(hdr->bsid, 8) - 8; |
|
hdr->sample_rate = ff_ac3_freqs[hdr->fscod] >> hdr->halfratecod; |
|
hdr->bit_rate = (ff_ac3_bitratetab[hdr->frmsizecod>>1] * 1000) >> hdr->halfratecod; |
|
hdr->channels = ff_ac3_channels[hdr->acmod] + hdr->lfeon; |
|
hdr->frame_size = ff_ac3_frame_sizes[hdr->frmsizecod][hdr->fscod] * 2; |
|
|
|
return 0; |
|
}
|
|
|