layer3.c

MP3的代码很实用 MP3的代码很实用

          }
          mc--;
        }
        if( (a & (0x8>>i)) ) {
          max[lwin] = cb;
          part2remain--;
          if(part2remain < 0) {
            part2remain++;
            break;
          }
	   GET1BIT();
          if(rval) 
            *xrpnt = -gainpow2[(-v) & 3]>>(v >> 2);			// -v;
          else
            *xrpnt =  gainpow2[(-v) & 3]>>(v >> 2);			// v
        }
        else
          *xrpnt = 0;
        xrpnt += step;
      }
    }
 
    while( m < me ) {
      if(!mc) {
        mc = *m++;
        xrpnt = ((real *) xr) + *m++;
        if( (*m++) == 3)
          step = 1;
        else
          step = 3;
        m++; /* cb */
      }
      mc--;
      *xrpnt = 0;
      xrpnt += step;
      *xrpnt = 0;
      xrpnt += step;
/* we could add a little opt. here:
 * if we finished a band for window 3 or a long band
 * further bands could copied in a simple loop without a
 * special 'map' decoding
 */
    }

    gr_info->maxband[0] = max[0]+1;
    gr_info->maxband[1] = max[1]+1;
    gr_info->maxband[2] = max[2]+1;
    gr_info->maxbandl = max[3]+1;

    {
      int rmax = max[0] > max[1] ? max[0] : max[1];
      rmax = (rmax > max[2] ? rmax : max[2]) + 1;
      gr_info->maxb = rmax ? shortLimit[sfreq][rmax] : longLimit[sfreq][max[3]+1];
    }

  }
  else {
	/*
     * decoding with 'long' BandIndex table (block_type != 2)
     */
    int *pretab = gr_info->preflag ? pretab1 : pretab2;
    int i,max = -1;
    int cb = 0;
    register int *m = map[sfreq][2];
    register real v = 0;
    register int mc = 0;

	/*
     * long hash table values
     */
    for(i=0;i<3;i++) {
      int lp = l[i];
      struct newhuff *h = ht+gr_info->table_select[i];

      for(;lp;lp--,mc--) {
        int x,y;

        if(!mc) {
          mc = *m++;
          v = gr_info->pow2gain + (((*scf++) + (*pretab++)) << shift);
          cb = *m++;
        }
        {
          register short *val = h->table;
          while((y=*val++)<0) {
	     GET1BIT();
            if (rval)
              val -= y;
            part2remain--;
          }
          x = y >> 4;
          y &= 0xf;
        }
        if (x == 15) {
          max = cb;
          part2remain -= h->linbits+1;
          x += getbits(h->linbits);
          deq_pow(x, v);			// ispow[x] * v;
          GET1BIT();
          if(rval)
            *xrpnt++ = -deq;
          else
            *xrpnt++ = deq;
        }
        else if(x) {
          max = cb;
          deq_pow(x, v);			// ispow[x] * v;
          GET1BIT();
          if(rval)
            *xrpnt++ = -deq;
          else
            *xrpnt++ = deq;
          part2remain--;
        }
        else
          *xrpnt++ = 0;

        if (y == 15) {
          max = cb;
          part2remain -= h->linbits+1;
          y += getbits(h->linbits);
          deq_pow(y, v);			// ispow[y] * v;
	   GET1BIT();
          if(rval)
            *xrpnt++ = -deq;
          else
            *xrpnt++ = deq;
        }
        else if(y) {
          max = cb;
          deq_pow(y, v);			// ispow[y] * v;
          GET1BIT();
          if(rval)
            *xrpnt++ = -deq;
          else
            *xrpnt++ = deq;
          part2remain--;
        }
        else
          *xrpnt++ = 0;
      }
    }

	/*
     * short (count1table) values
     */
    for(;l3 && (part2remain > 0);l3--) {
      struct newhuff *h = htc+gr_info->count1table_select;
      register short *val = h->table;
      register short a;

      while((a=*val++)<0) {
        part2remain--;
        if(part2remain < 0) {
          part2remain++;
          a = 0;
          break;
        }
	GET1BIT();
        if (rval)
          val -= a;
      }

      for(i=0;i<4;i++) {
        if(!(i & 1)) {
          if(!mc) {
            mc = *m++;
            cb = *m++;
            v = gr_info->pow2gain + (((*scf++) + (*pretab++)) << shift);
          }
          mc--;
        }
        if ( (a & (0x8>>i)) ) {
          max = cb;
          part2remain--;
          if(part2remain < 0) {
            part2remain++;
            break;
          }
	   GET1BIT();	  
          if(rval)
            *xrpnt++ = -gainpow2[(-v) & 3]>>(v >> 2);			// -v;
          else
            *xrpnt++ =  gainpow2[(-v) & 3]>>(v >> 2);			// v;
        }
        else
          *xrpnt++ = 0;
      }
    }

	/* 
     * zero part
     */
    for(i=(&xr[SBLIMIT][0]-xrpnt)>>1;i;i--) {
      *xrpnt++ = 0;
      *xrpnt++ = 0;
    }

    gr_info->maxbandl = max+1;
    gr_info->maxb = longLimit[sfreq][gr_info->maxbandl];
  }

  while( part2remain > 16 ) {
    getbits(16); /* Dismiss stuffing Bits */
    part2remain -= 16;
  }
  if(part2remain > 0)
    getbits(part2remain);
  else if(part2remain < 0) {
//    fprintf(stderr,"mpg123: Can't rewind stream by %d bits!\n",-part2remain);
    return 1; /* -> error */
  }
  return 0;
}
#endif

/* 
 * III_stereo: calculate real channel values for Joint-I-Stereo-mode
 */
static void III_i_stereo(real xr_buf[2][SBLIMIT][SSLIMIT],int *scalefac,
   struct gr_info_s *gr_info,int sfreq,int ms_stereo,int lsf)
{
      real (*xr)[SBLIMIT*SSLIMIT] = (real (*)[SBLIMIT*SSLIMIT] ) xr_buf;
      struct bandInfoStruct *bi = &bandInfo[sfreq];
      real *tab1,*tab2;

      if(lsf) {
        int p = gr_info->scalefac_compress & 0x1;
	    if(ms_stereo) {
          tab1 = pow1_2[p]; tab2 = pow2_2[p];		// 24bit
        }
        else {
          tab1 = pow1_1[p]; tab2 = pow2_1[p];		// 24bit
        }
      }
      else {
        if(ms_stereo) {
          tab1 = tan1_2; tab2 = tan2_2;			// 24bit
        }
        else {
          tab1 = tan1_1; tab2 = tan2_1;			// 24bit
        }
      }

      if (gr_info->block_type == 2)
      {
         int lwin,do_l = 0;
         if( gr_info->mixed_block_flag )
           do_l = 1;

         for (lwin=0;lwin<3;lwin++) /* process each window */
         {
             /* get first band with zero values */
           int is_p,sb,idx,sfb = gr_info->maxband[lwin];  /* sfb is minimal 3 for mixed mode */
           if(sfb > 3)
             do_l = 0;

           for(;sfb<12;sfb++)
           {
             is_p = scalefac[sfb*3+lwin-gr_info->mixed_block_flag]; /* scale: 0-15 */ 
             if(is_p != 7) {
               real t1,t2;
               sb = bi->shortDiff[sfb];
               idx = bi->shortIdx[sfb] + lwin;
               t1 = tab1[is_p]; t2 = tab2[is_p];
               for (; sb > 0; sb--,idx+=3)
               {
                 real v = xr[0][idx];
                 xr[0][idx] = MUL24(v, t1);
                 xr[1][idx] = MUL24(v, t2);
               }
             }
           }

#if 1
/* in the original: copy 10 to 11 , here: copy 11 to 12 
maybe still wrong??? (copy 12 to 13?) */
           is_p = scalefac[11*3+lwin-gr_info->mixed_block_flag]; /* scale: 0-15 */
           sb = bi->shortDiff[12];
           idx = bi->shortIdx[12] + lwin;
#else
           is_p = scalefac[10*3+lwin-gr_info->mixed_block_flag]; /* scale: 0-15 */
           sb = bi->shortDiff[11];
           idx = bi->shortIdx[11] + lwin;
#endif
           if(is_p != 7)
           {
             real t1,t2;
             t1 = tab1[is_p]; t2 = tab2[is_p];
             for ( ; sb > 0; sb--,idx+=3 )
             {  
               real v = xr[0][idx];
               xr[0][idx] = MUL24(v, t1);
               xr[1][idx] = MUL24(v, t2);
             }
           }
         } /* end for(lwin; .. ; . ) */

         if (do_l)
         {
/* also check l-part, if ALL bands in the three windows are 'empty'
 * and mode = mixed_mode 
 */
           int sfb = gr_info->maxbandl;
           int idx = bi->longIdx[sfb];

           for ( ; sfb<8; sfb++ )
           {
             int sb = bi->longDiff[sfb];
             int is_p = scalefac[sfb]; /* scale: 0-15 */
             if(is_p != 7) {
               real t1,t2;
               t1 = tab1[is_p]; t2 = tab2[is_p];
               for ( ; sb > 0; sb--,idx++)
               {
                 real v = xr[0][idx];
                 xr[0][idx] = MUL24(v, t1);
                 xr[1][idx] = MUL24(v, t2);
               }
             }
             else 
               idx += sb;
           }
         }     
      } 
      else /* ((gr_info->block_type != 2)) */
      {
        int sfb = gr_info->maxbandl;
        int is_p,idx = bi->longIdx[sfb];
        for ( ; sfb<21; sfb++)
        {
          int sb = bi->longDiff[sfb];
          is_p = scalefac[sfb]; /* scale: 0-15 */
          if(is_p != 7) {
            real t1,t2;
            t1 = tab1[is_p]; t2 = tab2[is_p];
            for ( ; sb > 0; sb--,idx++)
            {
               real v = xr[0][idx];
               xr[0][idx] = MUL24(v, t1);
               xr[1][idx] = MUL24(v, t2);
            }
          }
          else
            idx += sb;
        }

        is_p = scalefac[20]; /* copy l-band 20 to l-band 21 */
        if(is_p != 7)
        {
          int sb;
          real t1 = tab1[is_p],t2 = tab2[is_p]; 

          for ( sb = bi->longDiff[21]; sb > 0; sb--,idx++ )
          {
            real v = xr[0][idx];
            xr[0][idx] = MUL24(v, t1);
            xr[1][idx] = MUL24(v, t2);
          }
        }
      } /* ... */
}

void III_antialias(real xr[SBLIMIT][SSLIMIT],struct gr_info_s *gr_info);

#if 0
static void III_antialias(real xr[SBLIMIT][SSLIMIT],struct gr_info_s *gr_info)
{
   int sblim;

   if(gr_info->block_type == 2)
   {
      if(!gr_info->mixed_block_flag) 
        return;
      sblim = 1; 
   }
   else {
     sblim = gr_info->maxb-1;
   }

   /* 31 alias-reduction operations between each pair of sub-bands */
   /* with 8 butterflies between each pair                         */

   {
     int sb;
     real *xr1=(real *) xr[1];

     for(sb=sblim;sb;sb--,xr1+=10)
     {
       real *cs=aa_cs,*ca=aa_ca;
       real *xr2 = xr1;

       for(ss=7;ss>=0;ss--)
       {       /* upper and lower butterfly inputs */
         register real bu = *--xr2,bd = *xr1;
         *xr2   = MUL24(bu, *cs  ) - MUL24(bd, *ca  );
         *xr1++ = MUL24(bd, *cs++) + MUL24(bu, *ca++);
       }
     }
  }
}
#endif

void dct36(real *inbuf,real *o1,real *o2,real *wintab,real *tsbuf);

#if 0
/*
 DCT insipired by Jeff Tsay's DCT from the maplay package
 this is an optimized version with manual unroll.

 References:
 [1] S. Winograd: "On Computing the Discrete Fourier Transform",
     Mathematics of Computation, Volume 32, Number 141, January 1978,
     Pages 175-199
*/

static void dct36(real *inbuf,real *o1,real *o2,real *wintab,real *tsbuf)
{
  {
    register real *in = inbuf;
/*
 * Modified by DSA 2003.11.05 but it is no used here 
 */   
    in[17]+=in[16]; in[16]+=in[15]; in[15]+=in[14];
    in[14]+=in[13]; in[13]+=in[12]; in[12]+=in[11];
    in[11]+=in[10]; in[10]+=in[9];  in[9] +=in[8];