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Diffstat (limited to 'contrib/ffmpeg/libavcodec/ac3.c')
| -rw-r--r-- | contrib/ffmpeg/libavcodec/ac3.c | 287 |
1 files changed, 287 insertions, 0 deletions
diff --git a/contrib/ffmpeg/libavcodec/ac3.c b/contrib/ffmpeg/libavcodec/ac3.c new file mode 100644 index 000000000..3749d02f0 --- /dev/null +++ b/contrib/ffmpeg/libavcodec/ac3.c @@ -0,0 +1,287 @@ +/* + * 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; + + /* special case, if snroffset is -960, set all bap's to zero */ + if(snroffset == -960) { + memset(bap, 0, 256); + return; + } + + 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; +} |