parse.c

/*
 * parse.c
 * Copyright (C) 2000-2002 Michel Lespinasse <[email protected]>
 * Copyright (C) 1999-2000 Aaron Holtzman <[email protected]>
 *
 * This file is part of a52dec, a free ATSC A-52 stream decoder.
 * See http://liba52.sourceforge.net/ for updates.
 *
 * a52dec is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * a52dec 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include "config.h"

//#include <stdlib.h>

void    __cdecl free(void *);
void *  __cdecl malloc(size_t);

#include <string.h>
#include <inttypes.h>

#include "a52.h"
#include "a52_internal.h"
#include "bitstream.h"
#include "tables.h"

#ifdef HAVE_MEMALIGN
/* some systems have memalign() but no declaration for it */
void * memalign (size_t align, size_t size);
#else
/* assume malloc alignment is sufficient */
#define memalign(align,size) malloc (size)
#endif

typedef struct {
    sample_t q1[2];
    sample_t q2[2];
    sample_t q4;
    int q1_ptr;
    int q2_ptr;
    int q4_ptr;
} quantizer_t;

static uint8_t halfrate[12] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3};

a52_state_t * a52_init (uint32_t mm_accel)
{
    a52_state_t * state;
    int i;

    state = malloc (sizeof (a52_state_t));
    if (state == NULL)
        return NULL;

    state->samples = memalign (16, 256 * 12 * sizeof (sample_t));
    if (state->samples == NULL) {
        free (state);
        return NULL;
    }

    for (i = 0; i < 256 * 12; i++)
        state->samples[i] = 0;

    state->downmixed = 1;

    state->lfsr_state = 1;

    a52_imdct_init (mm_accel);

    return state;
}

sample_t * a52_samples (a52_state_t * state)
{
    return state->samples;
}

int a52_syncinfo (uint8_t * buf, int * flags,
                  int * sample_rate, int * bit_rate)
{
    static int rate[] = { 32,  40,  48,  56,  64,  80,  96, 112,
                         128, 160, 192, 224, 256, 320, 384, 448,
                         512, 576, 640};
    static uint8_t lfeon[8] = {0x10, 0x10, 0x04, 0x04, 0x04, 0x01, 0x04, 0x01};
    int frmsizecod;
    int bitrate;
    int half;
    int acmod;

    if ((buf[0] != 0x0b) || (buf[1] != 0x77))   /* syncword */
        return 0;

    if (buf[5] >= 0x60)         /* bsid >= 12 */
        return 0;
    half = halfrate[buf[5] >> 3];

    /* acmod, dsurmod and lfeon */
    acmod = buf[6] >> 5;
    *flags = ((((buf[6] & 0xf8) == 0x50) ? A52_DOLBY : acmod) |
              ((buf[6] & lfeon[acmod]) ? A52_LFE : 0));

    frmsizecod = buf[4] & 63;
    if (frmsizecod >= 38)
        return 0;
    bitrate = rate [frmsizecod >> 1];
    *bit_rate = (bitrate * 1000) >> half;

    switch (buf[4] & 0xc0) {
    case 0:
        *sample_rate = 48000 >> half;
        return 4 * bitrate;
    case 0x40:
        *sample_rate = 44100 >> half;
        return 2 * (320 * bitrate / 147 + (frmsizecod & 1));
    case 0x80:
        *sample_rate = 32000 >> half;
        return 6 * bitrate;
    default:
        return 0;
    }
}

int a52_frame (a52_state_t * state, uint8_t * buf, int * flags,
               sample_t * level, sample_t bias)
{
    static sample_t clev[4] = {LEVEL_3DB, LEVEL_45DB, LEVEL_6DB, LEVEL_45DB};
    static sample_t slev[4] = {LEVEL_3DB, LEVEL_6DB, 0, LEVEL_6DB};
    int chaninfo;
    int acmod;

    state->fscod = buf[4] >> 6;
    state->halfrate = halfrate[buf[5] >> 3];
    state->acmod = acmod = buf[6] >> 5;

    a52_bitstream_set_ptr (state, buf + 6);
    bitstream_get (state, 3);   /* skip acmod we already parsed */

    if ((acmod == 2) && (bitstream_get (state, 2) == 2))        /* dsurmod */
        acmod = A52_DOLBY;

    if ((acmod & 1) && (acmod != 1))
        state->clev = clev[bitstream_get (state, 2)];   /* cmixlev */

    if (acmod & 4)
        state->slev = slev[bitstream_get (state, 2)];   /* surmixlev */

    state->lfeon = bitstream_get (state, 1);

    state->output = a52_downmix_init (acmod, *flags, level,
                                      state->clev, state->slev);
    if (state->output < 0)
        return 1;
    if (state->lfeon && (*flags & A52_LFE))
        state->output |= A52_LFE;
    *flags = state->output;
    /* the 2* compensates for differences in imdct */
    state->dynrng = state->level = 2 * *level;
    state->bias = bias;
    state->dynrnge = 1;
    state->dynrngcall = NULL;
    state->cplba.deltbae = DELTA_BIT_NONE;
    state->ba[0].deltbae = state->ba[1].deltbae = state->ba[2].deltbae =
        state->ba[3].deltbae = state->ba[4].deltbae = DELTA_BIT_NONE;

    chaninfo = !acmod;
    do {
        bitstream_get (state, 5);       /* dialnorm */
        if (bitstream_get (state, 1))   /* compre */
            bitstream_get (state, 8);   /* compr */
        if (bitstream_get (state, 1))   /* langcode */
            bitstream_get (state, 8);   /* langcod */
        if (bitstream_get (state, 1))   /* audprodie */
            bitstream_get (state, 7);   /* mixlevel + roomtyp */
    } while (chaninfo--);

    bitstream_get (state, 2);           /* copyrightb + origbs */

    if (bitstream_get (state, 1))       /* timecod1e */
        bitstream_get (state, 14);      /* timecod1 */
    if (bitstream_get (state, 1))       /* timecod2e */
        bitstream_get (state, 14);      /* timecod2 */

    if (bitstream_get (state, 1)) {     /* addbsie */
        int addbsil;

        addbsil = bitstream_get (state, 6);
        do {
            bitstream_get (state, 8);   /* addbsi */
        } while (addbsil--);
    }

    return 0;
}

void a52_dynrng (a52_state_t * state,
                 sample_t (* call) (sample_t, void *), void * data)
{
    state->dynrnge = 0;
    if (call) {
        state->dynrnge = 1;
        state->dynrngcall = call;
        state->dynrngdata = data;
    }
}

static int parse_exponents (a52_state_t * state, int expstr, int ngrps,
                            uint8_t exponent, uint8_t * dest)
{
    int exps;

    while (ngrps--) {
        exps = bitstream_get (state, 7);

        exponent += exp_1[exps];
        if (exponent > 24)
            return 1;

        switch (expstr) {
        case EXP_D45:
            *(dest++) = exponent;
            *(dest++) = exponent;
        case EXP_D25:
            *(dest++) = exponent;
        case EXP_D15:
            *(dest++) = exponent;
        }

        exponent += exp_2[exps];
        if (exponent > 24)
            return 1;

        switch (expstr) {
        case EXP_D45:
            *(dest++) = exponent;
            *(dest++) = exponent;
        case EXP_D25:
            *(dest++) = exponent;
        case EXP_D15:
            *(dest++) = exponent;
        }

        exponent += exp_3[exps];
        if (exponent > 24)
            return 1;

        switch (expstr) {
        case EXP_D45:
            *(dest++) = exponent;
            *(dest++) = exponent;
        case EXP_D25:
            *(dest++) = exponent;
        case EXP_D15:
            *(dest++) = exponent;
        }
    }   

    return 0;
}

static int parse_deltba (a52_state_t * state, int8_t * deltba)
{
    int deltnseg, deltlen, delta, j;

    memset (deltba, 0, 50);

    deltnseg = bitstream_get (state, 3);
    j = 0;
    do {
        j += bitstream_get (state, 5);
        deltlen = bitstream_get (state, 4);
        delta = bitstream_get (state, 3);
        delta -= (delta >= 4) ? 3 : 4;
        if (!deltlen)
            continue;
        if (j + deltlen >= 50)
            return 1;
        while (deltlen--)
            deltba[j++] = delta;
    } while (deltnseg--);

    return 0;
}

static inline int zero_snr_offsets (int nfchans, a52_state_t * state)
{
    int i;

    if ((state->csnroffst) ||
        (state->chincpl && state->cplba.bai >> 3) ||    /* cplinu, fsnroffst */
        (state->lfeon && state->lfeba.bai >> 3))        /* fsnroffst */
        return 0;
    for (i = 0; i < nfchans; i++)
        if (state->ba[i].bai >> 3)                      /* fsnroffst */
            return 0;
    return 1;
}

static inline int16_t dither_gen (a52_state_t * state)
{
    int16_t nstate;

    nstate = dither_lut[state->lfsr_state >> 8] ^ (state->lfsr_state << 8);
        
    state->lfsr_state = (uint16_t) nstate;

    return nstate;
}

static void coeff_get (a52_state_t * state, sample_t * coeff,
                       expbap_t * expbap, quantizer_t * quantizer,
                       sample_t level, int dither, int end)
{
    int i;
    uint8_t * exp;
    int8_t * bap;
    sample_t factor[25];

    for (i = 0; i <= 24; i++)
        factor[i] = scale_factor[i] * level;

    exp = expbap->exp;
    bap = expbap->bap;

    for (i = 0; i < end; i++) {
        int bapi;

        bapi = bap[i];
        switch (bapi) {
        case 0:
            if (dither) {
                coeff[i] = dither_gen (state) * LEVEL_3DB * factor[exp[i]];
                continue;
            } else {
                coeff[i] = 0;
                continue;
            }

        case -1:
            if (quantizer->q1_ptr >= 0) {
                coeff[i] = quantizer->q1[quantizer->q1_ptr--] * factor[exp[i]];
                continue;
            } else {
                int code;

                code = bitstream_get (state, 5);

                quantizer->q1_ptr = 1;
                quantizer->q1[0] = q_1_2[code];
                quantizer->q1[1] = q_1_1[code];
                coeff[i] = q_1_0[code] * factor[exp[i]];
                continue;
            }

        case -2:
            if (quantizer->q2_ptr >= 0) {
                coeff[i] = quantizer->q2[quantizer->q2_ptr--] * factor[exp[i]];
                continue;
            } else {
                int code;

                code = bitstream_get (state, 7);

                quantizer->q2_ptr = 1;
                quantizer->q2[0] = q_2_2[code];
                quantizer->q2[1] = q_2_1[code];
                coeff[i] = q_2_0[code] * factor[exp[i]];
                continue;
            }

        case 3:
            coeff[i] = q_3[bitstream_get (state, 3)] * factor[exp[i]];
            continue;

        case -3:
            if (quantizer->q4_ptr == 0) {
                quantizer->q4_ptr = -1;
                coeff[i] = quantizer->q4 * factor[exp[i]];
                continue;
            } else {
                int code;

                code = bitstream_get (state, 7);

                quantizer->q4_ptr = 0;
                quantizer->q4 = q_4_1[code];
                coeff[i] = q_4_0[code] * factor[exp[i]];
                continue;
            }

        case 4:
            coeff[i] = q_5[bitstream_get (state, 4)] * factor[exp[i]];
            continue;

        default:
            coeff[i] = ((bitstream_get_2 (state, bapi) << (16 - bapi)) *
                          factor[exp[i]]);
        }
    }
}

static void coeff_get_coupling (a52_state_t * state, int nfchans,
                                sample_t * coeff, sample_t (* samples)[256],
                                quantizer_t * quantizer, uint8_t dithflag[5])
{
    int cplbndstrc, bnd, i, i_end, ch;
    uint8_t * exp;
    int8_t * bap;
    sample_t cplco[5];

    exp = state->cpl_expbap.exp;
    bap = state->cpl_expbap.bap;
    bnd = 0;
    cplbndstrc = state->cplbndstrc;
    i = state->cplstrtmant;
    while (i < state->cplendmant) {
        i_end = i + 12;
        while (cplbndstrc & 1) {
            cplbndstrc >>= 1;
            i_end += 12;
        }
        cplbndstrc >>= 1;
        for (ch = 0; ch < nfchans; ch++)
            cplco[ch] = state->cplco[ch][bnd] * coeff[ch];
        bnd++;

        while (i < i_end) {
            sample_t cplcoeff;
            int bapi;

            bapi = bap[i];
            switch (bapi) {
            case 0:
                cplcoeff = LEVEL_3DB * scale_factor[exp[i]];
                for (ch = 0; ch < nfchans; ch++)
                    if ((state->chincpl >> ch) & 1) {
                        if (dithflag[ch])
                            samples[ch][i] = (cplcoeff * cplco[ch] *
                                              dither_gen (state));
                        else
                            samples[ch][i] = 0;
                    }
                i++;
                continue;

            case -1:
                if (quantizer->q1_ptr >= 0) {
                    cplcoeff = quantizer->q1[quantizer->q1_ptr--];
                    break;
                } else {
                    int code;

                    code = bitstream_get (state, 5);

                    quantizer->q1_ptr = 1;
                    quantizer->q1[0] = q_1_2[code];
                    quantizer->q1[1] = q_1_1[code];
                    cplcoeff = q_1_0[code];
                    break;
                }

            case -2:
                if (quantizer->q2_ptr >= 0) {
                    cplcoeff = quantizer->q2[quantizer->q2_ptr--];
                    break;
                } else {
                    int code;

                    code = bitstream_get (state, 7);

                    quantizer->q2_ptr = 1;
                    quantizer->q2[0] = q_2_2[code];
                    quantizer->q2[1] = q_2_1[code];
                    cplcoeff = q_2_0[code];
                    break;
                }

            case 3:
                cplcoeff = q_3[bitstream_get (state, 3)];
                break;

            case -3:
                if (quantizer->q4_ptr == 0) {
                    quantizer->q4_ptr = -1;
                    cplcoeff = quantizer->q4;
                    break;
                } else {
                    int code;

                    code = bitstream_get (state, 7);

                    quantizer->q4_ptr = 0;
                    quantizer->q4 = q_4_1[code];
                    cplcoeff = q_4_0[code];
                    break;
                }

            case 4:
                cplcoeff = q_5[bitstream_get (state, 4)];
                break;

            default:
                cplcoeff = bitstream_get_2 (state, bapi) << (16 - bapi);
            }

            cplcoeff *= scale_factor[exp[i]];
            for (ch = 0; ch < nfchans; ch++)
                if ((state->chincpl >> ch) & 1)
                    samples[ch][i] = cplcoeff * cplco[ch];
            i++;
        }
    }
}

int a52_block (a52_state_t * state)
{
    static const uint8_t nfchans_tbl[] = {2, 1, 2, 3, 3, 4, 4, 5, 1, 1, 2};
    static int rematrix_band[4] = {25, 37, 61, 253};
    int i, nfchans, chaninfo;
    uint8_t cplexpstr, chexpstr[5], lfeexpstr, do_bit_alloc, done_cpl;
    uint8_t blksw[5], dithflag[5];
    sample_t coeff[5];
    int chanbias;
    quantizer_t quantizer;
    sample_t * samples;

    nfchans = nfchans_tbl[state->acmod];

    for (i = 0; i < nfchans; i++)
        blksw[i] = bitstream_get (state, 1);

    for (i = 0; i < nfchans; i++)
        dithflag[i] = bitstream_get (state, 1);

    chaninfo = !state->acmod;
    do {
        if (bitstream_get (state, 1)) { /* dynrnge */
            int dynrng;

            dynrng = bitstream_get_2 (state, 8);
            if (state->dynrnge) {
                sample_t range;

                range = ((((dynrng & 0x1f) | 0x20) << 13) *
                         scale_factor[3 - (dynrng >> 5)]);
                if (state->dynrngcall)
                    range = state->dynrngcall (range, state->dynrngdata);
                state->dynrng = state->level * range;
            }
        }
    } while (chaninfo--);

    if (bitstream_get (state, 1)) {     /* cplstre */
        state->chincpl = 0;
        if (bitstream_get (state, 1)) { /* cplinu */
            static uint8_t bndtab[16] = {31, 35, 37, 39, 41, 42, 43, 44,
                                         45, 45, 46, 46, 47, 47, 48, 48};
            int cplbegf;
            int cplendf;
            int ncplsubnd;

            for (i = 0; i < nfchans; i++)
                state->chincpl |= bitstream_get (state, 1) << i;
            switch (state->acmod) {
            case 0: case 1:
                return 1;
            case 2:
                state->phsflginu = bitstream_get (state, 1);
            }
            cplbegf = bitstream_get (state, 4);
            cplendf = bitstream_get (state, 4);

            if (cplendf + 3 - cplbegf < 0)
                return 1;
            state->ncplbnd = ncplsubnd = cplendf + 3 - cplbegf;
            state->cplstrtbnd = bndtab[cplbegf];
            state->cplstrtmant = cplbegf * 12 + 37;
            state->cplendmant = cplendf * 12 + 73;

            state->cplbndstrc = 0;
            for (i = 0; i < ncplsubnd - 1; i++)
                if (bitstream_get (state, 1)) {
                    state->cplbndstrc |= 1 << i;
                    state->ncplbnd--;
                }
        }
    }

    if (state->chincpl) {       /* cplinu */
        int j, cplcoe;

        cplcoe = 0;
        for (i = 0; i < nfchans; i++)
            if ((state->chincpl) >> i & 1)
                if (bitstream_get (state, 1)) { /* cplcoe */
                    int mstrcplco, cplcoexp, cplcomant;

                    cplcoe = 1;
                    mstrcplco = 3 * bitstream_get (state, 2);
                    for (j = 0; j < state->ncplbnd; j++) {
                        cplcoexp = bitstream_get (state, 4);
                        cplcomant = bitstream_get (state, 4);
                        if (cplcoexp == 15)
                            cplcomant <<= 14;
                        else
                            cplcomant = (cplcomant | 0x10) << 13;
                        state->cplco[i][j] =
                            cplcomant * scale_factor[cplcoexp + mstrcplco];
                    }
                }
        if ((state->acmod == 2) && state->phsflginu && cplcoe)
            for (j = 0; j < state->ncplbnd; j++)
                if (bitstream_get (state, 1))   /* phsflg */
                    state->cplco[1][j] = -state->cplco[1][j];
    }

    if ((state->acmod == 2) && (bitstream_get (state, 1))) {    /* rematstr */
        int end;

        state->rematflg = 0;
        end = (state->chincpl) ? state->cplstrtmant : 253;      /* cplinu */
        i = 0;
        do
            state->rematflg |= bitstream_get (state, 1) << i;
        while (rematrix_band[i++] < end);
    }

    cplexpstr = EXP_REUSE;
    lfeexpstr = EXP_REUSE;
    if (state->chincpl) /* cplinu */
        cplexpstr = bitstream_get (state, 2);
    for (i = 0; i < nfchans; i++)
        chexpstr[i] = bitstream_get (state, 2);
    if (state->lfeon) 
        lfeexpstr = bitstream_get (state, 1);

    for (i = 0; i < nfchans; i++)
        if (chexpstr[i] != EXP_REUSE) {
            if ((state->chincpl >> i) & 1)
                state->endmant[i] = state->cplstrtmant;
            else {
                int chbwcod;

                chbwcod = bitstream_get (state, 6);
                if (chbwcod > 60)
                    return 1;
                state->endmant[i] = chbwcod * 3 + 73;
            }
        }

    do_bit_alloc = 0;

    if (cplexpstr != EXP_REUSE) {
        int cplabsexp, ncplgrps;

        do_bit_alloc = 64;
        ncplgrps = ((state->cplendmant - state->cplstrtmant) /
                    (3 << (cplexpstr - 1)));
        cplabsexp = bitstream_get (state, 4) << 1;
        if (parse_exponents (state, cplexpstr, ncplgrps, cplabsexp,
                             state->cpl_expbap.exp + state->cplstrtmant))
            return 1;
    }
    for (i = 0; i < nfchans; i++)
        if (chexpstr[i] != EXP_REUSE) {
            int grp_size, nchgrps;

            do_bit_alloc |= 1 << i;
            grp_size = 3 << (chexpstr[i] - 1);
            nchgrps = (state->endmant[i] + grp_size - 4) / grp_size;
            state->fbw_expbap[i].exp[0] = bitstream_get (state, 4);
            if (parse_exponents (state, chexpstr[i], nchgrps,
                                 state->fbw_expbap[i].exp[0],
                                 state->fbw_expbap[i].exp + 1))
                return 1;
            bitstream_get (state, 2);   /* gainrng */
        }
    if (lfeexpstr != EXP_REUSE) {
        do_bit_alloc |= 32;
        state->lfe_expbap.exp[0] = bitstream_get (state, 4);
        if (parse_exponents (state, lfeexpstr, 2, state->lfe_expbap.exp[0],
                             state->lfe_expbap.exp + 1))
            return 1;
    }

    if (bitstream_get (state, 1)) {     /* baie */
        do_bit_alloc = -1;
        state->bai = bitstream_get (state, 11);
    }
    if (bitstream_get (state, 1)) {     /* snroffste */
        do_bit_alloc = -1;
        state->csnroffst = bitstream_get (state, 6);
        if (state->chincpl)     /* cplinu */
            state->cplba.bai = bitstream_get (state, 7);
        for (i = 0; i < nfchans; i++)
            state->ba[i].bai = bitstream_get (state, 7);
        if (state->lfeon)
            state->lfeba.bai = bitstream_get (state, 7);
    }
    if ((state->chincpl) && (bitstream_get (state, 1))) { /* cplleake */
        do_bit_alloc |= 64;
        state->cplfleak = 9 - bitstream_get (state, 3);
        state->cplsleak = 9 - bitstream_get (state, 3);
    }

    if (bitstream_get (state, 1)) {     /* deltbaie */
        do_bit_alloc = -1;
        if (state->chincpl)     /* cplinu */
            state->cplba.deltbae = bitstream_get (state, 2);
        for (i = 0; i < nfchans; i++)
            state->ba[i].deltbae = bitstream_get (state, 2);
        if (state->chincpl &&   /* cplinu */
            (state->cplba.deltbae == DELTA_BIT_NEW) &&
            parse_deltba (state, state->cplba.deltba))
            return 1;
        for (i = 0; i < nfchans; i++)
            if ((state->ba[i].deltbae == DELTA_BIT_NEW) &&
                parse_deltba (state, state->ba[i].deltba))
                return 1;
    }

    if (do_bit_alloc) {
        if (zero_snr_offsets (nfchans, state)) {
            memset (state->cpl_expbap.bap, 0, sizeof (state->cpl_expbap.bap));
            for (i = 0; i < nfchans; i++)
                memset (state->fbw_expbap[i].bap, 0,
                        sizeof (state->fbw_expbap[i].bap));
            memset (state->lfe_expbap.bap, 0, sizeof (state->lfe_expbap.bap));
        } else {
            if (state->chincpl && (do_bit_alloc & 64))  /* cplinu */
                a52_bit_allocate (state, &state->cplba, state->cplstrtbnd,
                                  state->cplstrtmant, state->cplendmant,
                                  state->cplfleak << 8, state->cplsleak << 8,
                                  &state->cpl_expbap);
            for (i = 0; i < nfchans; i++)
                if (do_bit_alloc & (1 << i))
                    a52_bit_allocate (state, state->ba + i, 0, 0,
                                      state->endmant[i], 0, 0,
                                      state->fbw_expbap +i);
            if (state->lfeon && (do_bit_alloc & 32)) {
                state->lfeba.deltbae = DELTA_BIT_NONE;
                a52_bit_allocate (state, &state->lfeba, 0, 0, 7, 0, 0,
                                  &state->lfe_expbap);
            }
        }
    }

    if (bitstream_get (state, 1)) {     /* skiple */
        i = bitstream_get (state, 9);   /* skipl */
        while (i--)
            bitstream_get (state, 8);
    }

    samples = state->samples;
    if (state->output & A52_LFE)
        samples += 256; /* shift for LFE channel */

    chanbias = a52_downmix_coeff (coeff, state->acmod, state->output,
                                  state->dynrng, state->clev, state->slev);

    quantizer.q1_ptr = quantizer.q2_ptr = quantizer.q4_ptr = -1;
    done_cpl = 0;

    for (i = 0; i < nfchans; i++) {
        int j;

        coeff_get (state, samples + 256 * i, state->fbw_expbap +i, &quantizer,
                   coeff[i], dithflag[i], state->endmant[i]);

        if ((state->chincpl >> i) & 1) {
            if (!done_cpl) {
                done_cpl = 1;
                coeff_get_coupling (state, nfchans, coeff,
                                    (sample_t (*)[256])samples, &quantizer,
                                    dithflag);
            }
            j = state->cplendmant;
        } else
            j = state->endmant[i];
        do
            (samples + 256 * i)[j] = 0;
        while (++j < 256);
    }

    if (state->acmod == 2) {
        int j, end, band, rematflg;

        end = ((state->endmant[0] < state->endmant[1]) ?
               state->endmant[0] : state->endmant[1]);

        i = 0;
        j = 13;
        rematflg = state->rematflg;
        do {
            if (! (rematflg & 1)) {
                rematflg >>= 1;
                j = rematrix_band[i++];
                continue;
            }
            rematflg >>= 1;
            band = rematrix_band[i++];
            if (band > end)
                band = end;
            do {
                sample_t tmp0, tmp1;

                tmp0 = samples[j];
                tmp1 = (samples+256)[j];
                samples[j] = tmp0 + tmp1;
                (samples+256)[j] = tmp0 - tmp1;
            } while (++j < band);
        } while (j < end);
    }

    if (state->lfeon) {
        if (state->output & A52_LFE) {
            coeff_get (state, samples - 256, &state->lfe_expbap, &quantizer,
                       state->dynrng, 0, 7);
            for (i = 7; i < 256; i++)
                (samples-256)[i] = 0;
            a52_imdct_512 (samples - 256, samples + 1536 - 256, state->bias);
        } else {
            /* just skip the LFE coefficients */
            coeff_get (state, samples + 1280, &state->lfe_expbap, &quantizer,
                       0, 0, 7);
        }
    }

    i = 0;
    if (nfchans_tbl[state->output & A52_CHANNEL_MASK] < nfchans)
        for (i = 1; i < nfchans; i++)
            if (blksw[i] != blksw[0])
                break;

    if (i < nfchans) {
        if (state->downmixed) {
            state->downmixed = 0;
            a52_upmix (samples + 1536, state->acmod, state->output);
        }

        for (i = 0; i < nfchans; i++) {
            sample_t bias;

            bias = 0;
            if (!(chanbias & (1 << i)))
                bias = state->bias;

            if (coeff[i]) {
                if (blksw[i])
                    a52_imdct_256 (samples + 256 * i, samples + 1536 + 256 * i,
                                   bias);
                else 
                    a52_imdct_512 (samples + 256 * i, samples + 1536 + 256 * i,
                                   bias);
            } else {
                int j;

                for (j = 0; j < 256; j++)
                    (samples + 256 * i)[j] = bias;
            }
        }

        a52_downmix (samples, state->acmod, state->output, state->bias,
                     state->clev, state->slev);
    } else {
        nfchans = nfchans_tbl[state->output & A52_CHANNEL_MASK];

        a52_downmix (samples, state->acmod, state->output, 0,
                     state->clev, state->slev);

        if (!state->downmixed) {
            state->downmixed = 1;
            a52_downmix (samples + 1536, state->acmod, state->output, 0,
                         state->clev, state->slev);
        }

        if (blksw[0])
            for (i = 0; i < nfchans; i++)
                a52_imdct_256 (samples + 256 * i, samples + 1536 + 256 * i,
                               state->bias);
        else 
            for (i = 0; i < nfchans; i++)
                a52_imdct_512 (samples + 256 * i, samples + 1536 + 256 * i,
                               state->bias);
    }

    return 0;
}

void a52_free (a52_state_t * state)
{
    free (state->samples);
    free (state);
}

---