hvirtual/libmpeg3/audio/exponents.c

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/* 
 *
 *      exponents.c Copyright (C) Aaron Holtzman - May 1999
 *
 *  This file is part of libmpeg3
 *      
 *  libmpeg3 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, or (at your option)
 *  any later version.
 *   
 *  libmpeg3 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 GNU Make; see the file COPYING.  If not, write to
 *  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. 
 *
 */
 
 
#define MIN(x, y) ((x) > (y) ? (y) : (x))

#include "mpeg3audio.h"
#include <stdio.h>

/* Exponent defines */
#define UNPACK_FBW  1
#define UNPACK_CPL  2
#define UNPACK_LFE  4

static inline int mpeg3audio_ac3_exp_unpack_ch(unsigned int type,
                unsigned int expstr,
                unsigned int ngrps,
                unsigned int initial_exp, 
                unsigned short exps[], 
                unsigned short *dest)
{
        int i, j;
        int exp_acc;
        int exp_1, exp_2, exp_3;

        if(expstr == MPEG3_EXP_REUSE)
                return 0;

/* Handle the initial absolute exponent */
        exp_acc = initial_exp;
        j = 0;

/* In the case of a fbw channel then the initial absolute value is 
 * also an exponent */
        if(type != UNPACK_CPL)
                dest[j++] = exp_acc;

/* Loop through the groups and fill the dest array appropriately */
        for(i = 0; i < ngrps; i++)
        {
                if(exps[i] > 124)
                {
//                      fprintf(stderr, "mpeg3audio_ac3_exp_unpack_ch: Invalid exponent %d\n", exps[i]);
                        return 1;
                }

                exp_1 = exps[i] / 25;
                exp_2 = (exps[i] % 25) / 5;
                exp_3 = (exps[i] % 25) % 5;

                exp_acc += (exp_1 - 2);

                switch(expstr)
                {
                        case MPEG3_EXP_D45:
                                j = MIN(255, j);
                                dest[j++] = exp_acc;
                                j = MIN(255, j);
                                dest[j++] = exp_acc;
                        case MPEG3_EXP_D25:
                                j = MIN(255, j);
                                dest[j++] = exp_acc;
                        case MPEG3_EXP_D15:
                                j = MIN(255, j);
                                dest[j++] = exp_acc;
                }

                exp_acc += (exp_2 - 2);

                switch(expstr)
                {
                        case MPEG3_EXP_D45:
                                j = MIN(255, j);
                                dest[j++] = exp_acc;
                                j = MIN(255, j);
                                dest[j++] = exp_acc;
                        case MPEG3_EXP_D25:
                                j = MIN(255, j);
                                dest[j++] = exp_acc;
                        case MPEG3_EXP_D15:
                                j = MIN(255, j);
                                dest[j++] = exp_acc;
                }

                exp_acc += (exp_3 - 2);

                switch(expstr)
                {
                        case MPEG3_EXP_D45:
                                j = MIN(255, j);
                                dest[j++] = exp_acc;
                                j = MIN(255, j);
                                dest[j++] = exp_acc;
                        case MPEG3_EXP_D25:
                                j = MIN(255, j);
                                dest[j++] = exp_acc;
                        case MPEG3_EXP_D15:
                                j = MIN(255, j);
                                dest[j++] = exp_acc;
                }
        }
        return 0;
}

int mpeg3audio_ac3_exponent_unpack(mpeg3audio_t *audio,
                mpeg3_ac3bsi_t *bsi,
                mpeg3_ac3audblk_t *audblk)
{
        int i, result = 0;

        for(i = 0; i < bsi->nfchans; i++)
                result |= mpeg3audio_ac3_exp_unpack_ch(UNPACK_FBW, 
                        audblk->chexpstr[i], 
                        audblk->nchgrps[i], 
                        audblk->exps[i][0], 
                        &audblk->exps[i][1], 
                        audblk->fbw_exp[i]);

        if(audblk->cplinu && !result)
                result |= mpeg3audio_ac3_exp_unpack_ch(UNPACK_CPL, 
                        audblk->cplexpstr, 
                        audblk->ncplgrps, 
                        audblk->cplabsexp << 1, 
                        audblk->cplexps, 
                        &audblk->cpl_exp[audblk->cplstrtmant]);

        if(bsi->lfeon && !result)
                result |= mpeg3audio_ac3_exp_unpack_ch(UNPACK_LFE, 
                        audblk->lfeexpstr, 
                        2, 
                        audblk->lfeexps[0], 
                        &audblk->lfeexps[1], 
                        audblk->lfe_exp);
        return result;
}

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