cabac.c

TML的参考源代码

  int i = img->subblock_x;
  int j = img->subblock_y;
  int a, b;
  int act_ctx, act_ctx1;
  int act_sym;
  int mv_local_err;
  int mv_sign;
  int backward = se->value2 & 0x01;
  int k = (se->value2>>1); // MVD component

  MotionInfoContexts *ctx = img->currentSlice->mot_ctx;
  Macroblock *currMB = &img->mb_data[img->current_mb_nr];

  if(backward == 0)
  {
    step_h=img->fw_blc_size_h/BLOCK_SIZE;  // horizontal stepsize
    step_v=img->fw_blc_size_v/BLOCK_SIZE;  // vertical stepsize
  }
  else
  {
    step_h=img->bw_blc_size_h/BLOCK_SIZE;  // horizontal stepsize
    step_v=img->bw_blc_size_v/BLOCK_SIZE;  // vertical stepsize
  }

  if (j==0)
  {
    if (currMB->mb_available[0][1] == NULL)
      b = 0;
    else
      b = absm((currMB->mb_available[0][1])->mvd[backward][BLOCK_SIZE-1][i][k]);
  }
  else
    b = absm(currMB->mvd[backward][j-step_v][i][k]);

  if (i==0)
  {
    if (currMB->mb_available[1][0] == NULL)
      a = 0;
    else
      a = absm((currMB->mb_available[1][0])->mvd[backward][j][BLOCK_SIZE-1][k]);
  }
  else
    a = absm(currMB->mvd[backward][j][i-step_h][k]);

  if ((mv_local_err=a+b)<3)
    act_ctx = 5*k;
  else
  {
    if (mv_local_err>32)
      act_ctx=5*k+3;
    else
      act_ctx=5*k+2;
  }
  se->context = act_ctx;

  act_ctx1 = act_ctx;

  act_sym = biari_decode_symbol(dep_dp,&ctx->mv_res_contexts[0][act_ctx] );

  if (act_sym != 0)
  {
    act_ctx = 5*k+4;
    mv_sign = biari_decode_symbol(dep_dp, &ctx->mv_res_contexts[1][act_ctx] );
    act_ctx=5*k;
    act_sym = unary_mv_decode(dep_dp,ctx->mv_res_contexts[1]+act_ctx,3);
    act_sym++;

    if(mv_sign)
      act_sym = -act_sym;
  }
  se->value1 = act_sym;

#if TRACE
  fprintf(p_trace, "@%d      %s\t\t\t%3d \n",symbolCount++, se->tracestring, se->value1);
  fflush(p_trace);
#endif
}


/*!
 ************************************************************************
 * \brief
 *    This function is used to arithmetically decode the forward
 *    or backward bidirectional blocksize (for B frames only)
 ************************************************************************
 */
void readBiDirBlkSize2Buffer_CABAC( SyntaxElement *se,
                                    struct inp_par *inp,
                                    struct img_par *img,
                                    DecodingEnvironmentPtr dep_dp)
{
  int act_ctx;
  MotionInfoContexts *ctx = img->currentSlice->mot_ctx;

  act_ctx=4;

  // using the context models of mb_type
  se->value1 = unary_bin_max_decode(dep_dp,ctx->mb_type_contexts[1]+act_ctx,1,6);

#if TRACE
  fprintf(p_trace, "@%d%s\t\t\t%3d\n",symbolCount++, se->tracestring, se->value1);
  fflush(p_trace);
#endif
}


/*!
 ************************************************************************
 * \brief
 *    This function is used to arithmetically decode the macroblock
 *    type info of a given MB.
 ************************************************************************
 */
void readMB_typeInfoFromBuffer_CABAC( SyntaxElement *se,
                                      struct inp_par *inp,
                                      struct img_par *img,
                                      DecodingEnvironmentPtr dep_dp)
{
  int a, b;
  int act_ctx;
  int act_sym;
  int log_sym;
  int bin_sym;
  int mode_sym;
  int ct = 0;

  MotionInfoContexts *ctx = (img->currentSlice)->mot_ctx;
  Macroblock *currMB = &img->mb_data[img->current_mb_nr];

  int curr_mb_type;

  if(img->type == INTRA_IMG)  // INTRA-frame
  {
    if (currMB->mb_available[0][1] == NULL)
      b = 0;
    else
      b = (( (currMB->mb_available[0][1])->mb_type != 0) ? 1 : 0 );
    if (currMB->mb_available[1][0] == NULL)
      a = 0;
    else
      a = (( (currMB->mb_available[1][0])->mb_type != 0) ? 1 : 0 );

    act_ctx = a + b;
    act_sym = biari_decode_symbol(dep_dp, ctx->mb_type_contexts[0] + act_ctx);
    se->context = act_ctx; // store context

    if (act_sym==0) // 4x4 Intra
      curr_mb_type = act_sym;
    else // 16x16 Intra
    {
      act_sym = 1;
      act_ctx = 4;
      mode_sym =  biari_decode_symbol(dep_dp, ctx->mb_type_contexts[0] + act_ctx ); // decoding of AC/no AC
      act_sym += mode_sym*12;
      act_ctx = 5;
      // decoding of cbp: 0,1,2
        mode_sym =  biari_decode_symbol(dep_dp, ctx->mb_type_contexts[0] + act_ctx );
      if (mode_sym!=0)
      {
        act_ctx=6;
        mode_sym = biari_decode_symbol(dep_dp, ctx->mb_type_contexts[0] + act_ctx );
        act_sym+=4;
        if (mode_sym!=0)
            act_sym+=4;
          }
        // decoding of I pred-mode: 0,1,2,3
        act_ctx = 7;
        mode_sym =  biari_decode_symbol(dep_dp, ctx->mb_type_contexts[0] + act_ctx );
        act_sym += mode_sym*2;
        act_ctx = 8;
        mode_sym =  biari_decode_symbol(dep_dp, ctx->mb_type_contexts[0] + act_ctx );
        act_sym += mode_sym;
        curr_mb_type = act_sym;
    }
  }
  else
  {
    ct = 1;
    if (currMB->mb_available[0][1] == NULL)
      b = 0;
    else
      b = (( (currMB->mb_available[0][1])->mb_type != 0) ? 1 : 0 );
    if (currMB->mb_available[1][0] == NULL)
      a = 0;
    else
      a = (( (currMB->mb_available[1][0])->mb_type != 0) ? 1 : 0 );

      act_ctx = a + b;

      // decode unary part
    log_sym = biari_decode_symbol(dep_dp, &ctx->mb_type_contexts[1][act_ctx] );

    if (log_sym != 0)
    {
      act_ctx=4;
      log_sym=0;
      do
      {
        act_sym = biari_decode_symbol(dep_dp, &ctx->mb_type_contexts[1][act_ctx] );
        if (log_sym==0) act_ctx=5;
        log_sym++;
      }
      while ( (act_sym!=0) && (log_sym<2+((img->type == B_IMG_1 || img->type == B_IMG_MULT)?1:0)));
      if( (act_sym!=0) && (log_sym==2+((img->type == B_IMG_1 || img->type == B_IMG_MULT)?1:0))  )
        log_sym++;
    }
    act_sym = (1<<log_sym);


    // decode binary part
    if (log_sym!=0)
    {
      act_ctx=6;
      if (log_sym==(3+((img->type == B_IMG_1 || img->type == B_IMG_MULT)?1:0)) ) log_sym=2; // only 2 LSBs are actually set for mode 7-9 (P-frame) or 15-17 (B-frame)
        bin_sym=0;
      do
      {
        log_sym--;
        bin_sym <<=1;
        bin_sym |=  (biari_decode_symbol(dep_dp,  &ctx->mb_type_contexts[1][act_ctx] ));
      }
      while (log_sym!=0);
      act_sym += bin_sym;
    }
    act_sym--;

    if (act_sym<=8 || (((img->type == B_IMG_1 || img->type == B_IMG_MULT)?1:0) && act_sym<=16))
      curr_mb_type = act_sym;
    else  // additional info for 16x16 Intra-mode
    {
      act_ctx = 7;
      mode_sym =  biari_decode_symbol(dep_dp, ctx->mb_type_contexts[1] + act_ctx ); // decoding of AC/no AC
      act_sym += mode_sym*12;

      // decoding of cbp: 0,1,2
      act_ctx = 8;
      mode_sym = biari_decode_symbol(dep_dp, ctx->mb_type_contexts[1] + act_ctx );
      if (mode_sym != 0)
      {
        act_sym+=4;
        mode_sym = biari_decode_symbol(dep_dp, ctx->mb_type_contexts[1] + act_ctx );
        if (mode_sym != 0)
          act_sym+=4;
      }

      // decoding of I pred-mode: 0,1,2,3
      act_ctx = 9;
      mode_sym = biari_decode_symbol(dep_dp, ctx->mb_type_contexts[1] + act_ctx );
      act_sym += mode_sym*2;
      mode_sym = biari_decode_symbol(dep_dp, ctx->mb_type_contexts[1] + act_ctx );
      act_sym += mode_sym;
      curr_mb_type = act_sym;
    }
  }
    se->value1 = curr_mb_type;

#if TRACE
    fprintf(p_trace, "@%d%s\t\t\t%3d\n",symbolCount++, se->tracestring, se->value1);
    fflush(p_trace);
#endif
}

/*!
 ************************************************************************
 * \brief
 *    This function is used to arithmetically decode a pair of
 *    intra prediction modes of a given MB.
 ************************************************************************
 */
void readIntraPredModeFromBuffer_CABAC( SyntaxElement *se,
                                        struct inp_par *inp,
                                        struct img_par *img,
                                        DecodingEnvironmentPtr dep_dp)
{
  static int prev_sym = 0;
  static int count = 0; // to detect a new row of intra prediction modes

  TextureInfoContexts *ctx = img->currentSlice->tex_ctx;

  if (count % 2 == 0)
    prev_sym = 0;

  se->value1 = unary_bin_max_decode(dep_dp,ctx->ipr_contexts[prev_sym],1,5);
  prev_sym = se->value1;
  se->value2 = unary_bin_max_decode(dep_dp,ctx->ipr_contexts[prev_sym],1,5);
  prev_sym = se->value2;


  if(++count == MB_BLOCK_SIZE/2) // all modes of one MB have been processed
    count=0;

#if TRACE
  fprintf(p_trace, "@%d%s\t\t\t%3d\n",symbolCount++, se->tracestring, se->value1);
  fflush(p_trace);
#endif

}

/*!
 ************************************************************************
 * \brief
 *    This function is used to arithmetically decode the reference
 *    parameter of a given MB.
 ************************************************************************
 */
void readRefFrameFromBuffer_CABAC(  SyntaxElement *se,
                                    struct inp_par *inp,
                                    struct img_par *img,
                                    DecodingEnvironmentPtr dep_dp)
{
  MotionInfoContexts *ctx = img->currentSlice->mot_ctx;
  Macroblock *currMB = &img->mb_data[img->current_mb_nr];

  int a, b;
  int act_ctx;
  int act_sym;

  if (currMB->mb_available[0][1] == NULL)
    b = 0;
  else
      b = ( ((currMB->mb_available[0][1])->predframe_no != 0) ? 1 : 0);
  if (currMB->mb_available[1][0] == NULL)
    a = 0;
  else
      a = ( ((currMB->mb_available[1][0])->predframe_no != 0) ? 1 : 0);
  act_ctx = a + 2*b;
  se->context = act_ctx; // store context

  act_sym = biari_decode_symbol(dep_dp,ctx->ref_no_contexts + act_ctx );

  if (act_sym != 0)
  {
    act_ctx = 4;
    act_sym = unary_bin_decode(dep_dp,ctx->ref_no_contexts+act_ctx,1);
    act_sym++;
  }
  se->value1 = act_sym;

#if TRACE
  fprintf(p_trace, "@%d%s\t\t\t%3d",symbolCount++, se->tracestring, se->value1);
  fprintf(p_trace," c: %d :%d \n",ctx->ref_no_contexts[act_ctx].cum_freq[0],ctx->ref_no_contexts[act_ctx].cum_freq[1]);
  fflush(p_trace);
#endif
}

/*!
 ************************************************************************
 * \brief
 *    This function is used to arithmetically decode the motion
 *    vector data of a given MB.
 ************************************************************************
 */
void readMVDFromBuffer_CABAC(SyntaxElement *se,
                             struct inp_par *inp,
                             struct img_par *img,
                             DecodingEnvironmentPtr dep_dp)
{
  int step_h, step_v;
  int i = img->subblock_x;
  int j = img->subblock_y;
  int a, b;
  int act_ctx;
  int act_sym;
  int mv_pred_res;
  int mv_local_err;
  int mv_sign;
  int k = se->value2; // MVD component

  MotionInfoContexts *ctx = img->currentSlice->mot_ctx;
  Macroblock *currMB = &img->mb_data[img->current_mb_nr];

  step_h=BLOCK_STEP[img->mb_mode][0];
  step_v=BLOCK_STEP[img->mb_mode][1];

  if (j==0)
  {
    if (currMB->mb_available[0][1] == NULL)
      b = 0;
    else
      b = absm((currMB->mb_available[0][1])->mvd[0][BLOCK_SIZE-1][i][k]);
  }
  else
    b = absm(currMB->mvd[0][j-step_v][i][k]);

  if (i==0)
  {
    if (currMB->mb_available[1][0] == NULL)
      a = 0;
    else
      a = absm((currMB->mb_available[1][0])->mvd[0][j][BLOCK_SIZE-1][k]);
  }
  else
    a = absm(currMB->mvd[0][j][i-step_h][k]);

  if ((mv_local_err=a+b)<3)
    act_ctx = 5*k;
  else
  {
    if (mv_local_err>32)
      act_ctx=5*k+3;
    else
      act_ctx=5*k+2;
  }
    se->context = act_ctx;

    act_sym = biari_decode_symbol(dep_dp, &ctx->mv_res_contexts[0][act_ctx] );

    if (act_sym == 0)
        mv_pred_res = 0;
    else
    {
  
        act_ctx=5*k;
        act_sym = unary_mv_decode(dep_dp,ctx->mv_res_contexts[1]+act_ctx,3);
        act_sym++;
        act_ctx=5*k+4;
        mv_sign = biari_decode_symbol(dep_dp,&ctx->mv_res_contexts[1][act_ctx] );

        mv_pred_res = ((mv_sign != 0) ? (-act_sym) : act_sym);
    }
    se->value1 = mv_pred_res;

#if TRACE
    fprintf(p_trace, "@%d%s\t\t\t%3d\n",symbolCount++, se->tracestring, se->value1);
    fflush(p_trace);
#endif
}

/*!
 ************************************************************************