layer3.c

MP3的代码很实用 MP3的代码很实用

   };
   int numbits;
   int num0 = slen[0][gr_info->scalefac_compress];
   int num1 = slen[1][gr_info->scalefac_compress];

    if (gr_info->block_type == 2) 
    {
      int i=18;
      numbits = (num0 + num1) * 18;

      if (gr_info->mixed_block_flag) {
//         for (i=8;i;i--)
           *scf++ = getbits_fast(num0);
           *scf++ = getbits_fast(num0);
           *scf++ = getbits_fast(num0);
           *scf++ = getbits_fast(num0);
           *scf++ = getbits_fast(num0);
           *scf++ = getbits_fast(num0);
           *scf++ = getbits_fast(num0);
           *scf++ = getbits_fast(num0);
         i = 9;
         numbits -= num0; /* num0 * 17 + num1 * 18 */
      }

      for (;i;i--)
        *scf++ = getbits_fast(num0);
//      for (i = 18; i; i--)
        *scf++ = getbits_fast(num1);
        *scf++ = getbits_fast(num1);
        *scf++ = getbits_fast(num1);
        *scf++ = getbits_fast(num1);
        *scf++ = getbits_fast(num1);
        *scf++ = getbits_fast(num1);
        *scf++ = getbits_fast(num1);
        *scf++ = getbits_fast(num1);
		*scf++ = getbits_fast(num1);
		*scf++ = getbits_fast(num1);
		*scf++ = getbits_fast(num1);
		*scf++ = getbits_fast(num1);
		*scf++ = getbits_fast(num1);
		*scf++ = getbits_fast(num1);
		*scf++ = getbits_fast(num1);
		*scf++ = getbits_fast(num1);
		*scf++ = getbits_fast(num1);
		*scf++ = getbits_fast(num1);

      *scf++ = 0; *scf++ = 0; *scf++ = 0; /* short[13][0..2] = 0 */
    }
    else 
    {
      int i;
      int scfsi = gr_info->scfsi;

      if(scfsi < 0) { /* scfsi < 0 => granule == 0 */
//         for(i=11;i;i--)
           *scf++ = getbits_fast(num0);
           *scf++ = getbits_fast(num0);
           *scf++ = getbits_fast(num0);
           *scf++ = getbits_fast(num0);
           *scf++ = getbits_fast(num0);
           *scf++ = getbits_fast(num0);
		   *scf++ = getbits_fast(num0);
		   *scf++ = getbits_fast(num0);
		   *scf++ = getbits_fast(num0);
		   *scf++ = getbits_fast(num0);
		   *scf++ = getbits_fast(num0);
//         for(i=10;i;i--)
           *scf++ = getbits_fast(num1);
           *scf++ = getbits_fast(num1);
           *scf++ = getbits_fast(num1);
           *scf++ = getbits_fast(num1);
           *scf++ = getbits_fast(num1);
           *scf++ = getbits_fast(num1);
           *scf++ = getbits_fast(num1);
           *scf++ = getbits_fast(num1);
           *scf++ = getbits_fast(num1);
           *scf++ = getbits_fast(num1);
         numbits = (num0 + num1) * 10 + num0;
      }
      else {
        numbits = 0;
        if(!(scfsi & 0x8)) {
//          for (i=6;i;i--)
            *scf++ = getbits_fast(num0);
            *scf++ = getbits_fast(num0);
            *scf++ = getbits_fast(num0);
            *scf++ = getbits_fast(num0);
            *scf++ = getbits_fast(num0);
            *scf++ = getbits_fast(num0);
          numbits += num0 * 6;
        }
        else {
          *scf++ = 0; *scf++ = 0; *scf++ = 0;  /* set to ZERO necessary? */
          *scf++ = 0; *scf++ = 0; *scf++ = 0;
        }

        if(!(scfsi & 0x4)) {
//          for (i=5;i;i--)
            *scf++ = getbits_fast(num0);
            *scf++ = getbits_fast(num0);
            *scf++ = getbits_fast(num0);
            *scf++ = getbits_fast(num0);
            *scf++ = getbits_fast(num0);
          numbits += num0 * 5;
        }
        else {
          *scf++ = 0; *scf++ = 0; *scf++ = 0;  /* set to ZERO necessary? */
          *scf++ = 0; *scf++ = 0;
        }

        if(!(scfsi & 0x2)) {
//          for(i=5;i;i--)
            *scf++ = getbits_fast(num1);
            *scf++ = getbits_fast(num1);
            *scf++ = getbits_fast(num1);
            *scf++ = getbits_fast(num1);
            *scf++ = getbits_fast(num1);
          numbits += num1 * 5;
        }
        else {
          *scf++ = 0; *scf++ = 0; *scf++ = 0;  /* set to ZERO necessary? */
          *scf++ = 0; *scf++ = 0;
        }

        if(!(scfsi & 0x1)) {
//          for (i=5;i;i--)
            *scf++ = getbits_fast(num1);
            *scf++ = getbits_fast(num1);
            *scf++ = getbits_fast(num1);
            *scf++ = getbits_fast(num1);
            *scf++ = getbits_fast(num1);
          numbits += num1 * 5;
        }
        else {
          *scf++ = 0; *scf++ = 0; *scf++ = 0;  /* set to ZERO necessary? */
          *scf++ = 0; *scf++ = 0;
        }
      }

      *scf++ = 0;  /* no l[21] in original sources */
    }
    return numbits;
}
#endif

#if (defined MPEG2||defined MPEG25)
static int III_get_scale_factors_2(int *scf,struct gr_info_s *gr_info,int i_stereo)
{
  unsigned char *pnt;
  int i,j;
  unsigned int slen;
  int n = 0;
  int numbits = 0;

  static unsigned char stab[3][6][4] = {
   { { 6, 5, 5,5 } , { 6, 5, 7,3 } , { 11,10,0,0} ,
     { 7, 7, 7,0 } , { 6, 6, 6,3 } , {  8, 8,5,0} } ,
   { { 9, 9, 9,9 } , { 9, 9,12,6 } , { 18,18,0,0} ,
     {12,12,12,0 } , {12, 9, 9,6 } , { 15,12,9,0} } ,
   { { 6, 9, 9,9 } , { 6, 9,12,6 } , { 15,18,0,0} ,
     { 6,15,12,0 } , { 6,12, 9,6 } , {  6,18,9,0} } }; 

  if(i_stereo) /* i_stereo AND second channel -> do_layer3() checks this */
    slen = i_slen2[gr_info->scalefac_compress>>1];
  else
    slen = n_slen2[gr_info->scalefac_compress];

  gr_info->preflag = (slen>>15) & 0x1;

  n = 0;  
  if( gr_info->block_type == 2 ) {
    n++;
    if(gr_info->mixed_block_flag)
      n++;
  }

  pnt = stab[n][(slen>>12)&0x7];

  for(i=0;i<4;i++) {
    int num = slen & 0x7;
    slen >>= 3;
    if(num) {
      for(j=0;j<(int)(pnt[i]);j++)
        *scf++ = getbits_fast(num);
      numbits += pnt[i] * num;
    }
    else {
      for(j=0;j<(int)(pnt[i]);j++)
        *scf++ = 0;
    }
  }
  
  n = (n << 1) + 1;
  for(i=0;i<n;i++)
    *scf++ = 0;

  return numbits;
}
#endif

// x: 21bit xr, v: gainpow2index(24bit), return 24bit
/*real deq_pow(int x, int v)				
{
	int p, r, l;
	real pow43;
	real deq;

	if (x < 130) {
		pow43 = ispow[x];					// 21bit
		l = 0;
	}else if (x < 1025) {
		p = x >> 3;
		r = x & 7;
		pow43 = (ispow[p]>>3) * (8-r) + (ispow[p+1]>>3) * r;	// 21bit
		l = 4;
	} else {
		p = x >> 6;
		r = x & 63;
		pow43 = (ispow[p]>>6) * (64-r) + (ispow[p+1]>>6) * r;	// 21bit
		l = 8;
	}
	
	p = -v;
	r = p & 3;
	p = p >> 2;
	deq = (pow43>>13) * (gainpow2[r]>>10);				// 21-9 + 24-14 = 22
	deq = deq >> (-2-l-p);						// left shift l + p and shift (24-22)
	return deq;
}
*/

extern int III_dequantize_sample(real xr[SBLIMIT][SSLIMIT],int *scf,
   struct gr_info_s *gr_info,int sfreq,int part2bits);
#if 0
#define deq_pow(x,v) \
	{ \
		int p, r, l; \
		if      ((x)<130 ) { deq = ispow[(x)]; l = 0; } \
		else if ((x)<1025) { p = (x)>>3; r = (x)&7 ; deq = (ispow[p]>>3)*(8 -r)+(ispow[p+1]>>3)*r; l = 4; } \
		else               { p = (x)>>6; r = (x)&63; deq = (ispow[p]>>6)*(64-r)+(ispow[p+1]>>6)*r; l = 8; } \
		p = -(v); r = p&3; p = p>>2; \
		deq = (deq>>13)*(gainpow2[r]>>10); deq = deq>>(-2-l-p); \
	}

static int pretab1[22] = {0,0,0,0,0,0,0,0,0,0,0,1,1,1,1,2,2,3,3,3,2,0};
static int pretab2[22] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};

static int III_dequantize_sample(real xr[SBLIMIT][SSLIMIT],int *scf,
   struct gr_info_s *gr_info,int sfreq,int part2bits)
{
  int shift = 1 + gr_info->scalefac_scale;
  real *xrpnt = (real *) xr;
  int l[3],l3,*count;
  int part2remain = gr_info->part2_3_length - part2bits;
  int *me;
  real deq;

  {
    int bv       = gr_info->big_values;
    int region1  = gr_info->region1start;
    int region2  = gr_info->region2start;

    l3 = ((576>>1)-bv)>>1;
       
/*
 * we may lose the 'odd' bit here !! 
 * check this later again 
 */
    if(bv <= region1) {
      l[0] = bv; l[1] = 0; l[2] = 0;	  
    }
    else {
      l[0] = region1;
      if(bv <= region2) {
        l[1] = bv - l[0];  l[2] = 0;
      }
      else {
        l[1] = region2 - l[0]; l[2] = bv - region2;
      }
    }
  }
 
  if(gr_info->block_type == 2) {
    /*
     * decoding with short or mixed mode BandIndex table 
     */
    int i,max[4];
    int step=0,lwin=0,cb=0;
    register int v = 0;
    register int *m,mc;
	
	count = max;
    if(gr_info->mixed_block_flag) {
      /*max[3] = -1;
      max[0] = max[1] = max[2] = 2;*/   
      *count = 2; count++;
      *count = 2; count++;
      *count = 2; count++;
      *count = -1;
      m = map[sfreq][0];
      me = mapend[sfreq][0];
    }
    else {
      /*max[0] = max[1] = max[2] = max[3] = -1;*/
      *count = -1; count++;
      *count = -1; count++;
      *count = -1; count++;
      *count = -1;
      /* max[3] not really needed in this case */
      m = map[sfreq][1];
      me = mapend[sfreq][1];
    }

    mc = 0;
    for(i=0;i<2;i++) {
      int lp = l[i];
      struct newhuff *h = ht+gr_info->table_select[i];
      for(;lp;lp--,mc--) {
        register int x,y;
        if( (!mc) ) {
          mc = *m++;
          xrpnt = ((real *) xr) + (*m++);
          lwin = *m++;
          cb = *m++;
          if(lwin == 3) {
            v = gr_info->pow2gain + ((*scf++) << shift);
            step = 1;
          }
          else {
            v = gr_info->full_gain[lwin] + ((*scf++) << shift);
            step = 3;
          }
        }
        {
          register short *val = h->table;
          while((y=*val++)<0) {
	     GET1BIT();
            if (rval)
              val -= y;
            part2remain--;
          }
          x = y >> 4;
          y &= 0xf;
        }
        if(x == 15) {
          max[lwin] = 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[lwin] = cb;
          deq_pow(x, v);			// ispow[x] * v;
          GET1BIT();
          if(rval)
            *xrpnt = -deq;
          else
            *xrpnt = deq;
          part2remain--;
        }
        else
          *xrpnt = 0;
        xrpnt += step;
        if(y == 15) {
          max[lwin] = 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[lwin] = cb;
          deq_pow(y, v);			// ispow[y] * v;
          GET1BIT();
          if(rval)
            *xrpnt = -deq;
          else
            *xrpnt = deq;
          part2remain--;
        }
        else
          *xrpnt = 0;
        xrpnt += step;
      }
    }
    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++;
            xrpnt = ((real *) xr) + (*m++);
            lwin = *m++;
            cb = *m++;
            if(lwin == 3) {
              v = gr_info->pow2gain + ((*scf++) << shift);
              step = 1;
            }
            else {
              v = gr_info->full_gain[lwin] + ((*scf++) << shift);
              step = 3;
            }