layer3.c

来自「从FFMPEG转换而来的H264解码程序,VC下编译..」· C语言 代码 · 共 1,345 行 · 第 1/3 页

    }
    else {
      int i;
      int scfsi = gr_info->scfsi;

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

        if(!(scfsi & 0x4)) {
          for (i=0;i<5;i++)
            *scf++ = getbits_fast(ctx,num0);
          numbits += num0 * 5;
        }
        else {
          scf += 5;
        }

        if(!(scfsi & 0x2)) {
          for(i=0;i<5;i++)
            *scf++ = getbits_fast(ctx,num1);
          numbits += num1 * 5;
        }
        else {
          scf += 5;
        }

        if(!(scfsi & 0x1)) {
          for (i=0;i<5;i++)
            *scf++ = getbits_fast(ctx,num1);
          numbits += num1 * 5;
        }
        else {
           scf += 5;
        }
        *scf++ = 0;  /* no l[21] in original sources */
      }
    }
    return numbits;
}

static int III_get_scale_factors_2(mp3lib_ctx *ctx,int *scf,struct gr_info_s *gr_info,int i_stereo)
{
  const unsigned char *pnt;
  int i,j;
  unsigned int slen;
  int n = 0;
  int numbits = 0;

  static const 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(ctx,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;
}

static const 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 const 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};

#define getbitoffset() ((-ctx->bitindex)&0x7)
#define getbyte()      (*ctx->wordpointer++)

/*
 * Dequantize samples (includes huffman decoding)
 */
/* 24 is enough because tab13 has max. a 19 bit huffvector */
#define BITSHIFT ((sizeof(long)-1)*8)
#define REFRESH_MASK \
  while(num < BITSHIFT) { \
    mask |= ((unsigned long)getbyte())<<(BITSHIFT-num); \
    num += 8; \
    part2remain -= 8; }

static int III_dequantize_sample(mp3lib_ctx *ctx,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;
  int part2remain = gr_info->part2_3_length - part2bits;
  int *me;

  int num=getbitoffset();
  long mask;
  /* we must split this, because for num==0 the shift is undefined if you do it in one step */
  mask  = ((unsigned long) getbits(ctx,num))<<BITSHIFT;
  mask <<= 8-num;
  part2remain -= num;

  {
    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] = 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=3,cb=0;
    register real v = 0.0;
    register int *m,mc;

    if(gr_info->mixed_block_flag) {
      max[3] = -1;
      max[0] = max[1] = max[2] = 2;
      m = map[sfreq][0];
      me = mapend[sfreq][0];
    }
    else {
      max[0] = max[1] = max[2] = max[3] = -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;
          REFRESH_MASK;
          while((y=*val++)<0) {
            if (mask < 0)
              val -= y;
            num--;
            mask <<= 1;
          }
          x = y >> 4;
          y &= 0xf;
        }
        if(x == 15 && h->linbits) {
          max[lwin] = cb;
          REFRESH_MASK;
          x += ((unsigned long) mask) >> (BITSHIFT+8-h->linbits);
          num -= h->linbits+1;
          mask <<= h->linbits;
          if(mask < 0)
            *xrpnt = REAL_MUL(-ispow[x], v);
          else
            *xrpnt = REAL_MUL(ispow[x], v);
          mask <<= 1;
        }
        else if(x) {
          max[lwin] = cb;
          if(mask < 0)
            *xrpnt = REAL_MUL(-ispow[x], v);
          else
            *xrpnt = REAL_MUL(ispow[x], v);
          num--;
          mask <<= 1;
        }
        else
          *xrpnt = 0.0;
        xrpnt += step;
        if(y == 15 && h->linbits) {
          max[lwin] = cb;
          REFRESH_MASK;
          y += ((unsigned long) mask) >> (BITSHIFT+8-h->linbits);
          num -= h->linbits+1;
          mask <<= h->linbits;
          if(mask < 0)
            *xrpnt = REAL_MUL(-ispow[y], v);
          else
            *xrpnt = REAL_MUL(ispow[y], v);
          mask <<= 1;
        }
        else if(y) {
          max[lwin] = cb;
          if(mask < 0)
            *xrpnt = REAL_MUL(-ispow[y], v);
          else
            *xrpnt = REAL_MUL(ispow[y], v);
          num--;
          mask <<= 1;
        }
        else
          *xrpnt = 0.0;
        xrpnt += step;
      }
    }

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

      REFRESH_MASK;
      while((a=*val++)<0) {
        if (mask < 0)
          val -= a;
        num--;
        mask <<= 1;
      }
      if(part2remain+num <= 0) {
	num -= part2remain+num;
	break;
      }

      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;
            }
          }
          mc--;
        }
        if( (a & (0x8>>i)) ) {
          max[lwin] = cb;
          if(part2remain+num <= 0) {
            break;
          }
          if(mask < 0)
            *xrpnt = -v;
          else
            *xrpnt = v;
          num--;
          mask <<= 1;
        }
        else
          *xrpnt = 0.0;
        xrpnt += step;
      }
    }

    if(lwin < 3) { /* short band? */
      while(1) {
        for(;mc > 0;mc--) {
          *xrpnt = 0.0; xrpnt += 3; /* short band -> step=3 */
          *xrpnt = 0.0; xrpnt += 3;
        }
        if(m >= me)
          break;
        mc    = *m++;
        xrpnt = ((real *) xr) + *m++;
        if(*m++ == 0)
          break; /* optimize: field will be set to zero at the end of the function */
        m++; /* cb */
      }
    }

    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)
     */
    const int *pretab = gr_info->preflag ? pretab1 : pretab2;
    int i,max = -1;
    int cb = 0;
    int *m = map[sfreq][2];
    register real v = 0.0;
    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++;
          cb = *m++;
#ifdef CUT_HF
          if(cb == 21) {
            fprintf(stderr,"c");
            v = 0.0;
          }
          else
#endif
            v = gr_info->pow2gain[((*scf++) + (*pretab++)) << shift];

        }
        {
          register short *val = h->table;
          REFRESH_MASK;
          while((y=*val++)<0) {
            if (mask < 0)
              val -= y;
            num--;
            mask <<= 1;
          }
          x = y >> 4;
          y &= 0xf;
        }

        if (x == 15 && h->linbits) {
          max = cb;
	  REFRESH_MASK;
          x += ((unsigned long) mask) >> (BITSHIFT+8-h->linbits);
          num -= h->linbits+1;
          mask <<= h->linbits;
          if(mask < 0)
            *xrpnt++ = REAL_MUL(-ispow[x], v);
          else
            *xrpnt++ = REAL_MUL(ispow[x], v);
          mask <<= 1;
        }
        else if(x) {
          max = cb;
          if(mask < 0)
            *xrpnt++ = REAL_MUL(-ispow[x], v);
          else
            *xrpnt++ = REAL_MUL(ispow[x], v);
          num--;
          mask <<= 1;
        }
        else
          *xrpnt++ = 0.0;

        if (y == 15 && h->linbits) {
          max = cb;
	  REFRESH_MASK;
          y += ((unsigned long) mask) >> (BITSHIFT+8-h->linbits);
          num -= h->linbits+1;
          mask <<= h->linbits;
          if(mask < 0)
            *xrpnt++ = REAL_MUL(-ispow[y], v);
          else
            *xrpnt++ = REAL_MUL(ispow[y], v);
          mask <<= 1;
        }
        else if(y) {
          max = cb;
          if(mask < 0)
            *xrpnt++ = REAL_MUL(-ispow[y], v);
          else
            *xrpnt++ = REAL_MUL(ispow[y], v);
          num--;
          mask <<= 1;
        }
        else
          *xrpnt++ = 0.0;
      }
    }

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