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/*
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 * Common code between AC3 encoder and decoder
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 * Copyright (c) 2000 Fabrice Bellard.
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 *
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 * This file is part of FFmpeg.
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 *
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 * FFmpeg is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU Lesser General Public
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 * License as published by the Free Software Foundation; either
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 * version 2.1 of the License, or (at your option) any later version.
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 *
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 * FFmpeg is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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 * Lesser General Public License for more details.
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 *
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 * You should have received a copy of the GNU Lesser General Public
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 * License along with FFmpeg; if not, write to the Free Software
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 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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 */
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/**
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 * @file ac3.c
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 * Common code between AC3 encoder and decoder.
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 */
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#include "avcodec.h"
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#include "ac3.h"
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#include "ac3tab.h"
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#include "bitstream.h"
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static inline int calc_lowcomp1(int a, int b0, int b1, int c)
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{
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    if ((b0 + 256) == b1) {
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        a = c;
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    } else if (b0 > b1) {
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        a = FFMAX(a - 64, 0);
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    }
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    return a;
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}
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static inline int calc_lowcomp(int a, int b0, int b1, int bin)
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{
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    if (bin < 7) {
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        return calc_lowcomp1(a, b0, b1, 384);
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    } else if (bin < 20) {
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        return calc_lowcomp1(a, b0, b1, 320);
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    } else {
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        return FFMAX(a - 128, 0);
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    }
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}
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void ff_ac3_bit_alloc_calc_psd(int8_t *exp, int start, int end, int16_t *psd,
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                               int16_t *bndpsd)
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{
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    int bin, i, j, k, end1, v;
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    /* exponent mapping to PSD */
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    for(bin=start;bin<end;bin++) {
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        psd[bin]=(3072 - (exp[bin] << 7));
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    }
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    /* PSD integration */
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    j=start;
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    k=masktab[start];
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    do {
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        v=psd[j];
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        j++;
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        end1 = FFMIN(bndtab[k+1], end);
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        for(i=j;i<end1;i++) {
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            /* logadd */
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            int adr = FFMIN(FFABS(v - psd[j]) >> 1, 255);
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            v = FFMAX(v, psd[j]) + latab[adr];
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            j++;
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        }
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        bndpsd[k]=v;
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        k++;
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    } while (end > bndtab[k]);
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}
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void ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *bndpsd,
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                                int start, int end, int fgain, int is_lfe,
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                                int deltbae, int deltnseg, uint8_t *deltoffst,
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                                uint8_t *deltlen, uint8_t *deltba,
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                                int16_t *mask)
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{
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    int16_t excite[50]; /* excitation */
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    int bin, k;
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    int bndstrt, bndend, begin, end1, tmp;
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    int lowcomp, fastleak, slowleak;
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    /* excitation function */
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    bndstrt = masktab[start];
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    bndend = masktab[end-1] + 1;
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    if (bndstrt == 0) {
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        lowcomp = 0;
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        lowcomp = calc_lowcomp1(lowcomp, bndpsd[0], bndpsd[1], 384);
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        excite[0] = bndpsd[0] - fgain - lowcomp;
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        lowcomp = calc_lowcomp1(lowcomp, bndpsd[1], bndpsd[2], 384);
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        excite[1] = bndpsd[1] - fgain - lowcomp;
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        begin = 7;
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        for (bin = 2; bin < 7; bin++) {
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            if (!(is_lfe && bin == 6))
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                lowcomp = calc_lowcomp1(lowcomp, bndpsd[bin], bndpsd[bin+1], 384);
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            fastleak = bndpsd[bin] - fgain;
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            slowleak = bndpsd[bin] - s->sgain;
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            excite[bin] = fastleak - lowcomp;
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            if (!(is_lfe && bin == 6)) {
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                if (bndpsd[bin] <= bndpsd[bin+1]) {
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                    begin = bin + 1;
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                    break;
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                }
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            }
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        }
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        end1=bndend;
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        if (end1 > 22) end1=22;
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        for (bin = begin; bin < end1; bin++) {
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            if (!(is_lfe && bin == 6))
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                lowcomp = calc_lowcomp(lowcomp, bndpsd[bin], bndpsd[bin+1], bin);
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            fastleak = FFMAX(fastleak - s->fdecay, bndpsd[bin] - fgain);
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            slowleak = FFMAX(slowleak - s->sdecay, bndpsd[bin] - s->sgain);
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            excite[bin] = FFMAX(fastleak - lowcomp, slowleak);
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        }
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        begin = 22;
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    } else {
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        /* coupling channel */
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        begin = bndstrt;
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        fastleak = (s->cplfleak << 8) + 768;
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        slowleak = (s->cplsleak << 8) + 768;
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    }
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    for (bin = begin; bin < bndend; bin++) {
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        fastleak = FFMAX(fastleak - s->fdecay, bndpsd[bin] - fgain);
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        slowleak = FFMAX(slowleak - s->sdecay, bndpsd[bin] - s->sgain);
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        excite[bin] = FFMAX(fastleak, slowleak);
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    }
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    /* compute masking curve */
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    for (bin = bndstrt; bin < bndend; bin++) {
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        tmp = s->dbknee - bndpsd[bin];
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        if (tmp > 0) {
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            excite[bin] += tmp >> 2;
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        }
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        mask[bin] = FFMAX(hth[bin >> s->halfratecod][s->fscod], excite[bin]);
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    }
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    /* delta bit allocation */
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    if (deltbae == 0 || deltbae == 1) {
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        int band, seg, delta;
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        band = 0;
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        for (seg = 0; seg < deltnseg; seg++) {
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            band += deltoffst[seg];
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            if (deltba[seg] >= 4) {
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                delta = (deltba[seg] - 3) << 7;
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            } else {
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                delta = (deltba[seg] - 4) << 7;
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            }
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            for (k = 0; k < deltlen[seg]; k++) {
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                mask[band] += delta;
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                band++;
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            }
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        }
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    }
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}
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void ff_ac3_bit_alloc_calc_bap(int16_t *mask, int16_t *psd, int start, int end,
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                               int snroffset, int floor, uint8_t *bap)
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{
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    int i, j, k, end1, v, address;
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    /* special case, if snroffset is -960, set all bap's to zero */
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    if(snroffset == -960) {
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        memset(bap, 0, 256);
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        return;
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    }
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    i = start;
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    j = masktab[start];
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    do {
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        v = (FFMAX(mask[j] - snroffset - floor, 0) & 0x1FE0) + floor;
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        end1 = FFMIN(bndtab[j] + bndsz[j], end);
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        for (k = i; k < end1; k++) {
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            address = av_clip((psd[i] - v) >> 5, 0, 63);
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            bap[i] = baptab[address];
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            i++;
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        }
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    } while (end > bndtab[j++]);
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}
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/* AC3 bit allocation. The algorithm is the one described in the AC3
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   spec. */
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void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap,
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                                   int8_t *exp, int start, int end,
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                                   int snroffset, int fgain, int is_lfe,
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                                   int deltbae,int deltnseg,
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                                   uint8_t *deltoffst, uint8_t *deltlen,
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                                   uint8_t *deltba)
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{
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    int16_t psd[256];   /* scaled exponents */
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    int16_t bndpsd[50]; /* interpolated exponents */
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    int16_t mask[50];   /* masking value */
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    ff_ac3_bit_alloc_calc_psd(exp, start, end, psd, bndpsd);
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    ff_ac3_bit_alloc_calc_mask(s, bndpsd, start, end, fgain, is_lfe,
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                               deltbae, deltnseg, deltoffst, deltlen, deltba,
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                               mask);
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    ff_ac3_bit_alloc_calc_bap(mask, psd, start, end, snroffset, s->floor, bap);
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}
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/**
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 * Initializes some tables.
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 * note: This function must remain thread safe because it is called by the
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 *       AVParser init code.
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 */
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void ac3_common_init(void)
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{
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    int i, j, k, l, v;
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    /* compute bndtab and masktab from bandsz */
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    k = 0;
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    l = 0;
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    for(i=0;i<50;i++) {
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        bndtab[i] = l;
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        v = bndsz[i];
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        for(j=0;j<v;j++) masktab[k++]=i;
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        l += v;
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    }
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    bndtab[50] = l;
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}
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int ff_ac3_parse_header(const uint8_t buf[7], AC3HeaderInfo *hdr)
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{
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    GetBitContext gbc;
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    memset(hdr, 0, sizeof(*hdr));
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    init_get_bits(&gbc, buf, 54);
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    hdr->sync_word = get_bits(&gbc, 16);
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    if(hdr->sync_word != 0x0B77)
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        return -1;
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    /* read ahead to bsid to make sure this is AC-3, not E-AC-3 */
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    hdr->bsid = show_bits_long(&gbc, 29) & 0x1F;
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    if(hdr->bsid > 10)
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        return -2;
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    hdr->crc1 = get_bits(&gbc, 16);
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    hdr->fscod = get_bits(&gbc, 2);
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    if(hdr->fscod == 3)
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        return -3;
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    hdr->frmsizecod = get_bits(&gbc, 6);
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    if(hdr->frmsizecod > 37)
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        return -4;
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    skip_bits(&gbc, 5); // skip bsid, already got it
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    hdr->bsmod = get_bits(&gbc, 3);
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    hdr->acmod = get_bits(&gbc, 3);
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    if((hdr->acmod & 1) && hdr->acmod != 1) {
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        hdr->cmixlev = get_bits(&gbc, 2);
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    }
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    if(hdr->acmod & 4) {
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        hdr->surmixlev = get_bits(&gbc, 2);
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    }
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    if(hdr->acmod == 2) {
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        hdr->dsurmod = get_bits(&gbc, 2);
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    }
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    hdr->lfeon = get_bits1(&gbc);
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    hdr->halfratecod = FFMAX(hdr->bsid, 8) - 8;
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    hdr->sample_rate = ff_ac3_freqs[hdr->fscod] >> hdr->halfratecod;
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    hdr->bit_rate = (ff_ac3_bitratetab[hdr->frmsizecod>>1] * 1000) >> hdr->halfratecod;
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    hdr->channels = ff_ac3_channels[hdr->acmod] + hdr->lfeon;
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    hdr->frame_size = ff_ac3_frame_sizes[hdr->frmsizecod][hdr->fscod] * 2;
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    return 0;
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}