cabac.c

包含了从MPEG4的视频解码到H.264的视频编码部分的源代码

      currMB->cbp_bits   |= (1<< bit   );
      currMB->cbp_bits   |= (1<<(bit+4));
    }
    else
    {
      currMB->cbp_bits   |= (1<<bit);
    }
  }

  if (type!=LUMA_8x8)
  {
    //--- get bits from neighbouring blocks ---
    if (j==0)
    {
      if (currMB->mb_available[0][1])
      {
        upper_bit = BIT_SET(currMB->mb_available[0][1]->cbp_bits,bit+ystep_back);
      }
    }
    else
    {
      upper_bit = BIT_SET(currMB->cbp_bits,bit-ystep);
    }
    if (i==0)
    {
      if (currMB->mb_available[1][0])
      {
        left_bit = BIT_SET(currMB->mb_available[1][0]->cbp_bits,bit+xstep_back);
      }
    }
    else
    {
      left_bit = BIT_SET(currMB->cbp_bits,bit-1);
    }
    ctx = 2*upper_bit+left_bit;

    //===== encode symbol =====
    biari_encode_symbol (eep_dp, (short)cbp_bit, img->currentSlice->tex_ctx->bcbp_contexts[type2ctx_bcbp[type]]+ctx);
  }
}




//===== position -> ctx for MAP =====
//--- zig-zag scan ----
static const int  pos2ctx_map8x8 [] = { 0,  1,  2,  3,  4,  5,  5,  4,  4,  3,  3,  4,  4,  4,  5,  5,
                                        4,  4,  4,  4,  3,  3,  6,  7,  7,  7,  8,  9, 10,  9,  8,  7,
                                        7,  6, 11, 12, 13, 11,  6,  7,  8,  9, 14, 10,  9,  8,  6, 11,
                                       12, 13, 11,  6,  9, 14, 10,  9, 11, 12, 13, 11 ,14, 10, 12, 14}; // 15 CTX
static const int  pos2ctx_map8x4 [] = { 0,  1,  2,  3,  4,  5,  7,  8,  9, 10, 11,  9,  8,  6,  7,  8,
                                        9, 10, 11,  9,  8,  6, 12,  8,  9, 10, 11,  9, 13, 13, 14, 14}; // 15 CTX
static const int  pos2ctx_map4x4 [] = { 0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 14}; // 15 CTX
static const int* pos2ctx_map    [] = {pos2ctx_map4x4, pos2ctx_map4x4, pos2ctx_map8x8, pos2ctx_map8x4,
                                       pos2ctx_map8x4, pos2ctx_map4x4, pos2ctx_map4x4, pos2ctx_map4x4};
//--- interlace scan ----
static const int  pos2ctx_map8x8i[] = { 0,  1,  1,  2,  2,  3,  3,  4,  5,  6,  7,  7,  7,  8,  4,  5,
                                        6,  9, 10, 10,  8, 11, 12, 11,  9,  9, 10, 10,  8, 11, 12, 11,
                                        9,  9, 10, 10,  8, 11, 12, 11,  9,  9, 10, 10,  8, 13, 13,  9,
                                        9, 10, 10,  8, 13, 13,  9,  9, 10, 10, 14, 14, 14, 14, 14, 14}; // 15 CTX
static const int  pos2ctx_map8x4i[] = { 0,  1,  2,  3,  4,  5,  6,  3,  4,  5,  6,  3,  4,  7,  6,  8,
                                        9,  7,  6,  8,  9, 10, 11, 12, 12, 10, 11, 13, 13, 14, 14, 14}; // 15 CTX
static const int  pos2ctx_map4x8i[] = { 0,  1,  1,  1,  2,  3,  3,  4,  4,  4,  5,  6,  2,  7,  7,  8,
                                        8,  8,  5,  6,  9, 10, 10, 11, 11, 11, 12, 13, 13, 14, 14, 14}; // 15 CTX
static const int* pos2ctx_map_int[] = {pos2ctx_map4x4, pos2ctx_map4x4, pos2ctx_map8x8i,pos2ctx_map8x4i,
                                       pos2ctx_map4x8i,pos2ctx_map4x4, pos2ctx_map4x4, pos2ctx_map4x4};


//===== position -> ctx for LAST =====
static const int  pos2ctx_last8x8 [] = { 0,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,
                                         2,  2,  2,  2,  2,  2,  2,  2,  2,  2,  2,  2,  2,  2,  2,  2,
                                         3,  3,  3,  3,  3,  3,  3,  3,  4,  4,  4,  4,  4,  4,  4,  4,
                                         5,  5,  5,  5,  6,  6,  6,  6,  7,  7,  7,  7,  8,  8,  8,  8}; //  9 CTX
static const int  pos2ctx_last8x4 [] = { 0,  1,  1,  1,  1,  1,  1,  1,  2,  2,  2,  2,  2,  2,  2,  2,
                                         3,  3,  3,  3,  4,  4,  4,  4,  5,  5,  6,  6,  7,  7,  8,  8}; //  9 CTX
static const int  pos2ctx_last4x4 [] = { 0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15}; // 15 CTX
static const int* pos2ctx_last    [] = {pos2ctx_last4x4, pos2ctx_last4x4, pos2ctx_last8x8, pos2ctx_last8x4,
                                        pos2ctx_last8x4, pos2ctx_last4x4, pos2ctx_last4x4, pos2ctx_last4x4};




/*!
 ****************************************************************************
 * \brief
 *    Write Significance MAP
 ****************************************************************************
 */
void write_significance_map (Macroblock* currMB, EncodingEnvironmentPtr eep_dp, int type, int coeff[], int coeff_ctr)
{
  short k, sig, last;
  int   k0      = 0;
  int   k1      = maxpos[type]-1;

  int               fld       = ( img->field_picture || ( mb_adaptive && img->field_mode ) );
  BiContextTypePtr  map_ctx   = ( fld ? img->currentSlice->tex_ctx-> fld_map_contexts[type2ctx_map [type]]
                                      : img->currentSlice->tex_ctx->     map_contexts[type2ctx_map [type]] );
  BiContextTypePtr  last_ctx  = ( fld ? img->currentSlice->tex_ctx->fld_last_contexts[type2ctx_last[type]]
                                      : img->currentSlice->tex_ctx->    last_contexts[type2ctx_last[type]] );

  if (!c1isdc[type])
  {
    k0++; k1++; coeff--;
  }

  for (k=k0; k<k1; k++) // if last coeff is reached, it has to be significant
  {
    sig   = (coeff[k]!=0 ? 1 : 0);

    if (img->pstruct)
      biari_encode_symbol  (eep_dp, sig,  map_ctx+pos2ctx_map_int [type][k]);
    else
      biari_encode_symbol  (eep_dp, sig,  map_ctx+pos2ctx_map     [type][k]);
    if (sig)
    {
      last = (--coeff_ctr==0 ? 1 : 0);

      biari_encode_symbol(eep_dp, last, last_ctx+pos2ctx_last[type][k]);
      if (last)
      {
        return;
      }
    }
  }
}


/*!
 ****************************************************************************
 * \brief
 *    Write Levels
 ****************************************************************************
 */
void write_significant_coefficients (Macroblock* currMB, EncodingEnvironmentPtr eep_dp, int type, int coeff[])
{
  int   i;
  int   absLevel;
  int   ctx;
  short sign;
  short greater_one;
  int   c1 = 1;
  int   c2 = 0;

  for (i=maxpos[type]-1; i>=0; i--)
  {
    if (coeff[i]!=0)
    {
      if (coeff[i]>0) {absLevel =  coeff[i];  sign = 0;}
      else            {absLevel = -coeff[i];  sign = 1;}

      greater_one = (absLevel>1 ? 1 : 0);

      //--- if coefficient is one ---
      ctx = min(c1,4);
      biari_encode_symbol (eep_dp, greater_one, img->currentSlice->tex_ctx->one_contexts[type2ctx_one[type]] + ctx);

      if (greater_one)
      {
        ctx = min(c2,4);
        unary_exp_golomb_level_encode(eep_dp, absLevel-2, img->currentSlice->tex_ctx->abs_contexts[type2ctx_abs[type]] + ctx);
        c1 = 0;
        c2++;
      }
      else if (c1)
      {
        c1++;
      }
      biari_encode_symbol_eq_prob (eep_dp, sign);
    }
  }
}



/*!
 ****************************************************************************
 * \brief
 *    Write Block-Transform Coefficients
 ****************************************************************************
 */
void writeRunLevel2Buffer_CABAC (SyntaxElement *se, EncodingEnvironmentPtr eep_dp)
{
  static int  coeff[64];
  static int  coeff_ctr = 0;
  static int  pos       = 0;

  Macroblock* currMB    = &img->mb_data[img->current_mb_nr];
  int         i;

  //--- accumulate run-level information ---
  if (se->value1 != 0)
  {
    for (i=0; i<se->value2; i++) coeff[pos++] = 0; coeff[pos++] = se->value1; coeff_ctr++;
    return;
  }
  else
  {
    for (; pos<64; pos++) coeff[pos] = 0;
  }

  //===== encode CBP-BIT =====
  write_and_store_CBP_block_bit     (currMB, eep_dp, se->context, coeff_ctr>0?1:0);

  if (coeff_ctr>0)
  {
    //===== encode significance map =====
    write_significance_map          (currMB, eep_dp, se->context, coeff, coeff_ctr);

    //===== encode significant coefficients =====
    write_significant_coefficients  (currMB, eep_dp, se->context, coeff);
  }

  //--- reset counters ---
  pos = coeff_ctr = 0;
}




/*!
 ************************************************************************
 * \brief
 *    Unary binarization and encoding of a symbol by using
 *    one or two distinct models for the first two and all
 *    remaining bins
*
************************************************************************/
void unary_bin_encode(EncodingEnvironmentPtr eep_dp,
                      unsigned int symbol,
                      BiContextTypePtr ctx,
                      int ctx_offset)
{
  unsigned int l;
  BiContextTypePtr ictx;

  if (symbol==0)
  {
    biari_encode_symbol(eep_dp, 0, ctx );
    return;
  }
  else
  {
    biari_encode_symbol(eep_dp, 1, ctx );
    l=symbol;
    ictx=ctx+ctx_offset;
    while ((--l)>0)
      biari_encode_symbol(eep_dp, 1, ictx);
    biari_encode_symbol(eep_dp, 0, ictx);
  }
  return;
}

/*!
 ************************************************************************
 * \brief
 *    Unary binarization and encoding of a symbol by using
 *    one or two distinct models for the first two and all
 *    remaining bins; no terminating "0" for max_symbol
 *    (finite symbol alphabet)
 ************************************************************************
 */
void unary_bin_max_encode(EncodingEnvironmentPtr eep_dp,
                          unsigned int symbol,
                          BiContextTypePtr ctx,
                          int ctx_offset,
                          unsigned int max_symbol)
{
  unsigned int l;
  BiContextTypePtr ictx;

  if (symbol==0)
  {
    biari_encode_symbol(eep_dp, 0, ctx );
    return;
  }
  else
  {
    biari_encode_symbol(eep_dp, 1, ctx );
    l=symbol;
    ictx=ctx+ctx_offset;
    while ((--l)>0)
      biari_encode_symbol(eep_dp, 1, ictx);
    if (symbol<max_symbol)
        biari_encode_symbol(eep_dp, 0, ictx);
  }
  return;
}



/*!
 ************************************************************************
 * \brief
 *    Exp Golomb binarization and encoding
 ************************************************************************
 */
void exp_golomb_encode_eq_prob( EncodingEnvironmentPtr eep_dp,
                                unsigned int symbol,
                                int k) 
{
  while(1)
  {
    if (symbol >= (unsigned int)(1<<k))   
    {
      biari_encode_symbol_eq_prob(eep_dp, 1);   //first unary part
      symbol = symbol - (1<<k);
      k++;
    }
    else                  
    {
      biari_encode_symbol_eq_prob(eep_dp, 0);   //now terminated zero of unary part
      while (k--)                               //next binary part
        biari_encode_symbol_eq_prob(eep_dp, (unsigned char)((symbol>>k)&1)); 
      break;
    }
  }

  return;
}

/*!
 ************************************************************************
 * \brief
 *    Exp-Golomb for Level Encoding
*
************************************************************************/
void unary_exp_golomb_level_encode( EncodingEnvironmentPtr eep_dp,
                                    unsigned int symbol,
                                    BiContextTypePtr ctx)
{
  unsigned int l,k;
  unsigned int exp_start = 13; // 15-2 : 0,1 level decision always sent

  if (symbol==0)
  {
    biari_encode_symbol(eep_dp, 0, ctx );
    return;
  }
  else
  {
    biari_encode_symbol(eep_dp, 1, ctx );
    l=symbol;
    k=1;
    while (((--l)>0) && (++k <= exp_start))
      biari_encode_symbol(eep_dp, 1, ctx);
    if (symbol < exp_start) biari_encode_symbol(eep_dp, 0, ctx);
    else exp_golomb_encode_eq_prob(eep_dp,symbol-exp_start,0);
  }
  return;
}



/*!
 ************************************************************************
 * \brief
 *    Exp-Golomb for MV Encoding
*
************************************************************************/
void unary_exp_golomb_mv_encode(EncodingEnvironmentPtr eep_dp,
                                unsigned int symbol,
                                BiContextTypePtr ctx,
                                unsigned int max_bin)
{
  unsigned int l,k;
  unsigned int bin=1;
  BiContextTypePtr ictx=ctx;
  unsigned int exp_start = 8; // 9-1 : 0 mvd decision always sent

  if (symbol==0)
  {
    biari_encode_symbol(eep_dp, 0, ictx );
    return;
  }
  else
  {
    biari_encode_symbol(eep_dp, 1, ictx );
    l=symbol;
    k=1;
    ictx++;
    while (((--l)>0) && (++k <= exp_start))
    {
      biari_encode_symbol(eep_dp, 1, ictx  );
      if ((++bin)==2) ictx++;
      if (bin==max_bin) ictx++;
    }
    if (symbol < exp_start) biari_encode_symbol(eep_dp, 0, ictx);
    else exp_golomb_encode_eq_prob(eep_dp,symbol-exp_start,3);
  }
  return;
}