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bit_allocate.c

/* 
 *  bit_allocate.c
 *
 *    Copyright (C) Aaron Holtzman - May 1999
 *
 *  This file is part of ac3dec, a free Dolby AC-3 stream decoder.
 *    
 *  ac3dec 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.
 *   
 *  ac3dec 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. 
 *
 */

#include <stdlib.h>
#include <string.h>
#include "ac3.h"
#include "ac3_internal.h"



static inline sint_16 logadd(sint_16 a,sint_16  b);
static sint_16 calc_lowcomp(sint_16 a,sint_16 b0,sint_16 b1,sint_16 bin);
static inline uint_16 min(sint_16 a,sint_16 b);
static inline uint_16 max(sint_16 a,sint_16 b);
static void ba_compute_psd(sint_16 start, sint_16 end, sint_16 exps[], 
            sint_16 psd[], sint_16 bndpsd[]);

static void ba_compute_excitation(sint_16 start, sint_16 end,sint_16 fgain,
            sint_16 fastleak, sint_16 slowleak, sint_16 is_lfe, sint_16 bndpsd[],
            sint_16 excite[]);
static void ba_compute_mask(sint_16 start, sint_16 end, uint_16 fscod,
            uint_16 deltbae, uint_16 deltnseg, uint_16 deltoffst[], uint_16 deltba[],
            uint_16 deltlen[], sint_16 excite[], sint_16 mask[]);
static void ba_compute_bap(sint_16 start, sint_16 end, sint_16 snroffset,
            sint_16 psd[], sint_16 mask[], sint_16 bap[]);

/* Misc LUTs for bit allocation process */

static sint_16 slowdec[]  = { 0x0f,  0x11,  0x13,  0x15  };
static sint_16 fastdec[]  = { 0x3f,  0x53,  0x67,  0x7b  };
static sint_16 slowgain[] = { 0x540, 0x4d8, 0x478, 0x410 };
static sint_16 dbpbtab[]  = { 0x000, 0x700, 0x900, 0xb00 };

static uint_16 floortab[] = { 0x2f0, 0x2b0, 0x270, 0x230, 0x1f0, 0x170, 0x0f0, 0xf800 };
static sint_16 fastgain[] = { 0x080, 0x100, 0x180, 0x200, 0x280, 0x300, 0x380, 0x400  };


static sint_16 bndtab[] = {  0,  1,  2,   3,   4,   5,   6,   7,   8,   9, 
                     10, 11, 12,  13,  14,  15,  16,  17,  18,  19,
                     20, 21, 22,  23,  24,  25,  26,  27,  28,  31,
                     34, 37, 40,  43,  46,  49,  55,  61,  67,  73,
                     79, 85, 97, 109, 121, 133, 157, 181, 205, 229 };

static sint_16 bndsz[]  = { 1,  1,  1,  1,  1,  1,  1,  1,  1,  1,
                     1,  1,  1,  1,  1,  1,  1,  1,  1,  1,
                     1,  1,  1,  1,  1,  1,  1,  1,  3,  3,
                     3,  3,  3,  3,  3,  6,  6,  6,  6,  6,
                     6, 12, 12, 12, 12, 24, 24, 24, 24, 24 };

static sint_16 masktab[] = { 0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15,
                     16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 28, 28, 29,
                     29, 29, 30, 30, 30, 31, 31, 31, 32, 32, 32, 33, 33, 33, 34, 34,
                     34, 35, 35, 35, 35, 35, 35, 36, 36, 36, 36, 36, 36, 37, 37, 37,
                     37, 37, 37, 38, 38, 38, 38, 38, 38, 39, 39, 39, 39, 39, 39, 40,
                     40, 40, 40, 40, 40, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41,
                     41, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 43, 43, 43,
                     43, 43, 43, 43, 43, 43, 43, 43, 43, 44, 44, 44, 44, 44, 44, 44,
                     44, 44, 44, 44, 44, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45,
                     45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 46, 46, 46,
                     46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46,
                     46, 46, 46, 46, 46, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47,
                     47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 48, 48, 48,
                     48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48,
                     48, 48, 48, 48, 48, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49,
                     49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49,  0,  0,  0 };


static sint_16 latab[] = { 0x0040, 0x003f, 0x003e, 0x003d, 0x003c, 0x003b, 0x003a, 0x0039,
                    0x0038, 0x0037, 0x0036, 0x0035, 0x0034, 0x0034, 0x0033, 0x0032,
                    0x0031, 0x0030, 0x002f, 0x002f, 0x002e, 0x002d, 0x002c, 0x002c,
                    0x002b, 0x002a, 0x0029, 0x0029, 0x0028, 0x0027, 0x0026, 0x0026,
                    0x0025, 0x0024, 0x0024, 0x0023, 0x0023, 0x0022, 0x0021, 0x0021,
                    0x0020, 0x0020, 0x001f, 0x001e, 0x001e, 0x001d, 0x001d, 0x001c,
                    0x001c, 0x001b, 0x001b, 0x001a, 0x001a, 0x0019, 0x0019, 0x0018,
                    0x0018, 0x0017, 0x0017, 0x0016, 0x0016, 0x0015, 0x0015, 0x0015,
                    0x0014, 0x0014, 0x0013, 0x0013, 0x0013, 0x0012, 0x0012, 0x0012,
                    0x0011, 0x0011, 0x0011, 0x0010, 0x0010, 0x0010, 0x000f, 0x000f,
                    0x000f, 0x000e, 0x000e, 0x000e, 0x000d, 0x000d, 0x000d, 0x000d,
                    0x000c, 0x000c, 0x000c, 0x000c, 0x000b, 0x000b, 0x000b, 0x000b,
                    0x000a, 0x000a, 0x000a, 0x000a, 0x000a, 0x0009, 0x0009, 0x0009,
                    0x0009, 0x0009, 0x0008, 0x0008, 0x0008, 0x0008, 0x0008, 0x0008,
                    0x0007, 0x0007, 0x0007, 0x0007, 0x0007, 0x0007, 0x0006, 0x0006,
                    0x0006, 0x0006, 0x0006, 0x0006, 0x0006, 0x0006, 0x0005, 0x0005,
                    0x0005, 0x0005, 0x0005, 0x0005, 0x0005, 0x0005, 0x0004, 0x0004,
                    0x0004, 0x0004, 0x0004, 0x0004, 0x0004, 0x0004, 0x0004, 0x0004,
                    0x0004, 0x0003, 0x0003, 0x0003, 0x0003, 0x0003, 0x0003, 0x0003,
                    0x0003, 0x0003, 0x0003, 0x0003, 0x0003, 0x0003, 0x0003, 0x0002,
                    0x0002, 0x0002, 0x0002, 0x0002, 0x0002, 0x0002, 0x0002, 0x0002,
                    0x0002, 0x0002, 0x0002, 0x0002, 0x0002, 0x0002, 0x0002, 0x0002,
                    0x0002, 0x0002, 0x0001, 0x0001, 0x0001, 0x0001, 0x0001, 0x0001,
                    0x0001, 0x0001, 0x0001, 0x0001, 0x0001, 0x0001, 0x0001, 0x0001,
                    0x0001, 0x0001, 0x0001, 0x0001, 0x0001, 0x0001, 0x0001, 0x0001,
                    0x0001, 0x0001, 0x0001, 0x0001, 0x0001, 0x0001, 0x0001, 0x0001,
                    0x0001, 0x0001, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000,
                    0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000,
                    0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000,
                    0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000,
                    0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000,
                    0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000,
                    0x0000, 0x0000, 0x0000, 0x0000};

static sint_16 hth[][50] = {{ 0x04d0, 0x04d0, 0x0440, 0x0400, 0x03e0, 0x03c0, 0x03b0, 0x03b0,  
                      0x03a0, 0x03a0, 0x03a0, 0x03a0, 0x03a0, 0x0390, 0x0390, 0x0390,  
                      0x0380, 0x0380, 0x0370, 0x0370, 0x0360, 0x0360, 0x0350, 0x0350,  
                      0x0340, 0x0340, 0x0330, 0x0320, 0x0310, 0x0300, 0x02f0, 0x02f0,
                      0x02f0, 0x02f0, 0x0300, 0x0310, 0x0340, 0x0390, 0x03e0, 0x0420,
                      0x0460, 0x0490, 0x04a0, 0x0460, 0x0440, 0x0440, 0x0520, 0x0800,
                      0x0840, 0x0840 },
                      
                    { 0x04f0, 0x04f0, 0x0460, 0x0410, 0x03e0, 0x03d0, 0x03c0, 0x03b0, 
                      0x03b0, 0x03a0, 0x03a0, 0x03a0, 0x03a0, 0x03a0, 0x0390, 0x0390, 
                      0x0390, 0x0380, 0x0380, 0x0380, 0x0370, 0x0370, 0x0360, 0x0360, 
                      0x0350, 0x0350, 0x0340, 0x0340, 0x0320, 0x0310, 0x0300, 0x02f0, 
                      0x02f0, 0x02f0, 0x02f0, 0x0300, 0x0320, 0x0350, 0x0390, 0x03e0, 
                      0x0420, 0x0450, 0x04a0, 0x0490, 0x0460, 0x0440, 0x0480, 0x0630, 
                      0x0840, 0x0840 },
                      
                    { 0x0580, 0x0580, 0x04b0, 0x0450, 0x0420, 0x03f0, 0x03e0, 0x03d0, 
                      0x03c0, 0x03b0, 0x03b0, 0x03b0, 0x03a0, 0x03a0, 0x03a0, 0x03a0, 
                      0x03a0, 0x03a0, 0x03a0, 0x03a0, 0x0390, 0x0390, 0x0390, 0x0390, 
                      0x0380, 0x0380, 0x0380, 0x0370, 0x0360, 0x0350, 0x0340, 0x0330, 
                      0x0320, 0x0310, 0x0300, 0x02f0, 0x02f0, 0x02f0, 0x0300, 0x0310, 
                      0x0330, 0x0350, 0x03c0, 0x0410, 0x0470, 0x04a0, 0x0460, 0x0440, 
                      0x0450, 0x04e0 }};


static sint_16 baptab[] = { 0,  1,  1,  1,  1,  1,  2,  2,  3,  3,  3,  4,  4,  5,  5,  6,
                     6,  6,  6,  7,  7,  7,  7,  8,  8,  8,  8,  9,  9,  9,  9, 10, 
                     10, 10, 10, 11, 11, 11, 11, 12, 12, 12, 12, 13, 13, 13, 13, 14,
                     14, 14, 14, 14, 14, 14, 14, 15, 15, 15, 15, 15, 15, 15, 15, 15 };

static sint_16 sdecay;
static sint_16 fdecay;
static sint_16 sgain;
static sint_16 dbknee;
static sint_16 floor;
static sint_16 psd[256];
static sint_16 bndpsd[256];
static sint_16 excite[256];
static sint_16 mask[256];

static inline uint_16
max(sint_16 a,sint_16 b)
{
      return (a > b ? a : b);
}
      
static inline uint_16
min(sint_16 a,sint_16 b)
{
      return (a < b ? a : b);
}

static inline sint_16 
logadd(sint_16 a,sint_16  b) 
{ 
      sint_16 c;
      sint_16 address;

      c = a - b; 
      address = min((abs(c) >> 1), 255); 
      
      if (c >= 0) 
            return(a + latab[address]); 
      else 
            return(b + latab[address]); 
}


void bit_allocate(uint_16 fscod, bsi_t *bsi, audblk_t *audblk)
{
      uint_16 i;
      sint_16 fgain;
      sint_16 snroffset;
      sint_16 start;
      sint_16 end;
      sint_16 fastleak;
      sint_16 slowleak;

      /* Only perform bit_allocation if the exponents have changed or we
       * have new sideband information */
      if (audblk->chexpstr[0]  == 0 && audblk->chexpstr[1] == 0 &&
                  audblk->chexpstr[2]  == 0 && audblk->chexpstr[3] == 0 &&
                  audblk->chexpstr[4]  == 0 && audblk->cplexpstr   == 0 &&
                  audblk->lfeexpstr    == 0 && audblk->baie        == 0 &&
                  audblk->snroffste    == 0 && audblk->deltbaie    == 0)
            return;

      /* Do some setup before we do the bit alloc */
      sdecay = slowdec[audblk->sdcycod]; 
      fdecay = fastdec[audblk->fdcycod];
      sgain = slowgain[audblk->sgaincod]; 
      dbknee = dbpbtab[audblk->dbpbcod]; 
      floor = floortab[audblk->floorcod]; 

      /* if all the SNR offset constants are zero then the whole block is zero */
      if(!audblk->csnroffst    && !audblk->fsnroffst[0] && 
             !audblk->fsnroffst[1] && !audblk->fsnroffst[2] && 
             !audblk->fsnroffst[3] && !audblk->fsnroffst[4] &&
             !audblk->cplfsnroffst && !audblk->lfefsnroffst)
      {
            memset(audblk->fbw_bap,0,sizeof(uint_16) * 256 * 5);
            memset(audblk->cpl_bap,0,sizeof(uint_16) * 256);
            memset(audblk->lfe_bap,0,sizeof(uint_16) * 7);
            return;
      }
             

      for(i = 0; i < bsi->nfchans; i++)
      {
            start = 0;
            end = audblk->endmant[i] ; 
            fgain = fastgain[audblk->fgaincod[i]]; 
            snroffset = (((audblk->csnroffst - 15) << 4) + audblk->fsnroffst[i]) << 2 ;
            fastleak = 0;
            slowleak = 0;

            ba_compute_psd(start, end, audblk->fbw_exp[i], psd, bndpsd);

            ba_compute_excitation(start, end , fgain, fastleak, slowleak, 0, bndpsd, excite);

            ba_compute_mask(start, end, fscod, audblk->deltbae[i], audblk->deltnseg[i], 
                        audblk->deltoffst[i], audblk->deltba[i], audblk->deltlen[i], excite, mask);

            ba_compute_bap(start, end, snroffset, psd, mask, audblk->fbw_bap[i]);
      }

      if(audblk->cplinu)
      {
            start = audblk->cplstrtmant; 
            end = audblk->cplendmant; 
            fgain = fastgain[audblk->cplfgaincod];
            snroffset = (((audblk->csnroffst - 15) << 4) + audblk->cplfsnroffst) << 2 ;
            fastleak = (audblk->cplfleak << 8) + 768; 
            slowleak = (audblk->cplsleak << 8) + 768;

            ba_compute_psd(start, end, audblk->cpl_exp, psd, bndpsd);

            ba_compute_excitation(start, end , fgain, fastleak, slowleak, 0, bndpsd, excite);

            ba_compute_mask(start, end, fscod, audblk->cpldeltbae, audblk->cpldeltnseg, 
                        audblk->cpldeltoffst, audblk->cpldeltba, audblk->cpldeltlen, excite, mask);

            ba_compute_bap(start, end, snroffset, psd, mask, audblk->cpl_bap);
      }

      if(bsi->lfeon)
      {
            start = 0;
            end = 7;
            fgain = fastgain[audblk->lfefgaincod];
            snroffset = (((audblk->csnroffst - 15) << 4) + audblk->lfefsnroffst) << 2 ;
            fastleak = 0;
            slowleak = 0;

            ba_compute_psd(start, end, audblk->lfe_exp, psd, bndpsd);

            ba_compute_excitation(start, end , fgain, fastleak, slowleak, 1, bndpsd, excite);

            /* Perform no delta bit allocation for lfe */
            ba_compute_mask(start, end, fscod, 2, 0, 0, 0, 0, excite, mask);

            ba_compute_bap(start, end, snroffset, psd, mask, audblk->lfe_bap);
      }
}


static void ba_compute_psd(sint_16 start, sint_16 end, sint_16 exps[], 
            sint_16 psd[], sint_16 bndpsd[])
{
      int bin,i,j,k;
      sint_16 lastbin = 0;
      
      /* Map the exponents into dBs */
      for (bin=start; bin<end; bin++) 
      { 
            psd[bin] = (3072 - (exps[bin] << 7)); 
      }

      /* Integrate the psd function over each bit allocation band */
      j = start; 
      k = masktab[start]; 
      
      do 
      { 
            lastbin = min(bndtab[k] + bndsz[k], end); 
            bndpsd[k] = psd[j]; 
            j++; 

            for (i = j; i < lastbin; i++) 
            { 
                  bndpsd[k] = logadd(bndpsd[k], psd[j]);
                  j++; 
            } 
            
            k++; 
      } while (end > lastbin);
}

static void ba_compute_excitation(sint_16 start, sint_16 end,sint_16 fgain,
            sint_16 fastleak, sint_16 slowleak, sint_16 is_lfe, sint_16 bndpsd[],
            sint_16 excite[])
{
      int bin;
      sint_16 bndstrt;
      sint_16 bndend;
      sint_16 lowcomp = 0;
      sint_16 begin = 0;

      /* Compute excitation function */
      bndstrt = masktab[start]; 
      bndend = masktab[end - 1] + 1; 
      
      if (bndstrt == 0) /* For fbw and lfe channels */ 
      { 
            lowcomp = calc_lowcomp(lowcomp, bndpsd[0], bndpsd[1], 0); 
            excite[0] = bndpsd[0] - fgain - lowcomp; 
            lowcomp = calc_lowcomp(lowcomp, bndpsd[1], bndpsd[2], 1);
            excite[1] = bndpsd[1] - fgain - lowcomp; 
            begin = 7 ; 
            
            /* Note: Do not call calc_lowcomp() for the last band of the lfe channel, (bin = 6) */ 
            for (bin = 2; bin < 7; bin++) 
            { 
                  if (!(is_lfe && (bin == 6)))
                        lowcomp = calc_lowcomp(lowcomp, bndpsd[bin], bndpsd[bin+1], bin); 
                  fastleak = bndpsd[bin] - fgain; 
                  slowleak = bndpsd[bin] - sgain; 
                  excite[bin] = fastleak - lowcomp; 
                  
                  if (!(is_lfe && (bin == 6)))
                  {
                        if (bndpsd[bin] <= bndpsd[bin+1]) 
                        {
                              begin = bin + 1 ; 
                              break; 
                        } 
                  }
            } 
            
            for (bin = begin; bin < min(bndend, 22); bin++) 
            { 
                  if (!(is_lfe && (bin == 6)))
                        lowcomp = calc_lowcomp(lowcomp, bndpsd[bin], bndpsd[bin+1], bin); 
                  fastleak -= fdecay ; 
                  fastleak = max(fastleak, bndpsd[bin] - fgain); 
                  slowleak -= sdecay ; 
                  slowleak = max(slowleak, bndpsd[bin] - sgain); 
                  excite[bin] = max(fastleak - lowcomp, slowleak); 
            } 
            begin = 22; 
      } 
      else /* For coupling channel */ 
      { 
            begin = bndstrt; 
      } 

      for (bin = begin; bin < bndend; bin++) 
      { 
            fastleak -= fdecay; 
            fastleak = max(fastleak, bndpsd[bin] - fgain); 
            slowleak -= sdecay; 
            slowleak = max(slowleak, bndpsd[bin] - sgain); 
            excite[bin] = max(fastleak, slowleak) ; 
      } 
}

static void ba_compute_mask(sint_16 start, sint_16 end, uint_16 fscod,
            uint_16 deltbae, uint_16 deltnseg, uint_16 deltoffst[], uint_16 deltba[],
            uint_16 deltlen[], sint_16 excite[], sint_16 mask[])
{
      int bin,k;
      sint_16 bndstrt;
      sint_16 bndend;
      sint_16 delta;

      bndstrt = masktab[start]; 
      bndend = masktab[end - 1] + 1; 

      /* Compute the masking curve */

      for (bin = bndstrt; bin < bndend; bin++) 
      { 
            if (bndpsd[bin] < dbknee) 
            { 
                  excite[bin] += ((dbknee - bndpsd[bin]) >> 2); 
            } 
            mask[bin] = max(excite[bin], hth[fscod][bin]);
      }
      
      /* Perform delta bit modulation if necessary */
      if ((deltbae == DELTA_BIT_REUSE) || (deltbae == DELTA_BIT_NEW)) 
      { 
            sint_16 band = 0; 
            sint_16 seg = 0; 
            
            for (seg = 0; seg < deltnseg+1; 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++; 
                  } 
            } 
      }
}

static void ba_compute_bap(sint_16 start, sint_16 end, sint_16 snroffset,
            sint_16 psd[], sint_16 mask[], sint_16 bap[])
{
      int i,j,k;
      sint_16 lastbin = 0;
      sint_16 address = 0;

      /* Compute the bit allocation pointer for each bin */
      i = start; 
      j = masktab[start]; 

      do 
      { 
            lastbin = min(bndtab[j] + bndsz[j], end); 
            mask[j] -= snroffset; 
            mask[j] -= floor; 
            
            if (mask[j] < 0) 
                  mask[j] = 0; 

            mask[j] &= 0x1fe0;
            mask[j] += floor; 
            for (k = i; k < lastbin; k++) 
            { 
                  address = (psd[i] - mask[j]) >> 5; 
                  address = min(63, max(0, address)); 
                  bap[i] = baptab[address]; 
                  i++; 
            } 
            j++; 
      } while (end > lastbin);
}

static sint_16 
calc_lowcomp(sint_16 a,sint_16 b0,sint_16 b1,sint_16 bin) 
{ 

      if (bin < 7) 
      { 
            if ((b0 + 256) == b1)
                  a = 384; 
            else if (b0 > b1) 
                  a = max(0, a - 64); 
      } 
      else if (bin < 20) 
      { 
            if ((b0 + 256) == b1) 
                  a = 320; 
            else if (b0 > b1) 
                  a = max(0, a - 64) ; 
      }
      else  
            a = max(0, a - 128); 
      
      return(a);
}


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