for(x=-2;x<4;x++) {
        pres_x = max(0,min(maxold_x,x_pos+x));
        result += imY[pres_y][pres_x]*COEF[x+2];
      }

      result1 = max(0, min(255, (result+16)/32));

      result = 0;
      pres_x = dx == 1 ? x_pos : x_pos+1;
      pres_x = max(0,min(maxold_x,pres_x));

      for(y=-2;y<4;y++) {
        pres_y = max(0,min(maxold_y,y_pos+y));
        result += imY[pres_y][pres_x]*COEF[y+2];
      }

      result2 = max(0, min(255, (result+16)/32));
      result = (result1+result2)/2;
    }
  }

  return result;
}
  
/*! 
 *************************************************************************************
 * \brief
 *    Performs the simulation of the packet losses, calls the error concealment funcs
 *    and copies the decoded images to the reference frame buffers of the decoders 
 *
 *************************************************************************************
 */
void UpdateDecoders()
{
  int k;
  for (k=0; k<input->NoOfDecoders; k++)
  {
    Build_Status_Map(decs->status_map); // simulates the packet losses
    Error_Concealment(decs->decY_best[k], decs->status_map, decs->decref[k]); // for the moment error concealment is just a "copy"
    // Move decoded frames to reference buffers: (at the decoders this is done 
    // without interpolation (upsampling) - upsampling is done while decoding
    DecOneForthPix(decs->decY_best[k], decs->decref[k]); 
  }
}
/*! 
 *************************************************************************************
 * \brief
 *    Copies one (reconstructed) image to the respective reference frame buffer
 *
 * \note
 *    This is used at the "many decoders in the encoder"
 * \param dY
 *    The reconstructed image
 * \param dref
 *    The reference buffer
 *************************************************************************************
 */
void DecOneForthPix(byte **dY, byte ***dref)
{
  int j, ref=IMG_NUMBER%img->buf_cycle;

  for (j=0; j<img->height; j++)
    memcpy(dref[ref][j], dY[j], img->width);
}

/*! 
 *************************************************************************************
 * \brief
 *    Gives the prediction residue for a 8x8 block
 *************************************************************************************
 */
void compute_residue_b8block (int b8block, int i16mode) // if not INTRA16x16 it has to be -1
{
  int i,j;
  int i0 = (b8block%2)<<3,   i1 = i0+8;
  int j0 = (b8block/2)<<3,   j1 = j0+8;

  if (i16mode>=0)
  {
    for (i=i0; i<i1; i++)
    for (j=j0; j<j1; j++)
    {
      decs->resY[j][i] = enc_picture->imgY[img->pix_y+j][img->pix_x+i] - img->mprr_2[i16mode][j][i];
    }
  }
  else
  {
    for (i=i0; i<i1; i++)
    for (j=j0; j<j1; j++)
    {
      decs->resY[j][i] = enc_picture->imgY[img->pix_y+j][img->pix_x+i] - img->mpr[i][j];
    }
  }
}

/*! 
 *************************************************************************************
 * \brief
 *    Gives the prediction residue for a macroblock
 *************************************************************************************
 */
void compute_residue_mb (int i16mode)
{
  compute_residue_b8block (0, i16mode);
  compute_residue_b8block (1, i16mode);
  compute_residue_b8block (2, i16mode);
  compute_residue_b8block (3, i16mode);
}


/*! 
 *************************************************************************************
 * \brief
 *    Builds a random status map showing whether each MB is received or lost, based
 *    on the packet loss rate and the slice structure.
 *
 * \param s_map
 *    The status map to be filled
 *************************************************************************************
 */
void Build_Status_Map(byte **s_map)
{
  int i,j,slice=-1,mb=0,jj,ii,packet_lost=0;

  jj = img->height/MB_BLOCK_SIZE;
  ii = img->width/MB_BLOCK_SIZE;
  
  for (j=0 ; j<jj; j++)
  for (i=0 ; i<ii; i++)
  {
    if (!input->slice_mode || img->mb_data[mb].slice_nr != slice) /* new slice */
    {
      packet_lost=0;
      if ((double)rand()/(double)RAND_MAX*100 < input->LossRateC)   packet_lost += 3;
      if ((double)rand()/(double)RAND_MAX*100 < input->LossRateB)   packet_lost += 2;
      if ((double)rand()/(double)RAND_MAX*100 < input->LossRateA)   packet_lost  = 1;
      slice++;
    }
    if (!packet_lost)
    {
      s_map[j][i]=0;  //! Packet OK
    }
    else
    {
      s_map[j][i]=packet_lost;
      if(input->partition_mode == 0)  s_map[j][i]=1;
    }
    mb++;
  }
}

/*! 
 *************************************************************************************
 * \brief
 *    Performs some sort of error concealment for the areas that are lost according
 *    to the status_map
 *    
 * \param inY
 *    Error concealment is performed on this frame imY[][]
 * \param s_map
 *    The status map shows which areas are lost.
 * \param refY
 *    The set of reference frames - may be used for the error concealment.
 *************************************************************************************
 */
void Error_Concealment(byte **inY, byte **s_map, byte ***refY)
{
  int mb_y, mb_x, mb_h, mb_w;
  mb_h = img->height/MB_BLOCK_SIZE;
  mb_w = img->width/MB_BLOCK_SIZE;
  
  for (mb_y=0; mb_y < mb_h; mb_y++)
  for (mb_x=0; mb_x < mb_w; mb_x++)
  {
    if (s_map[mb_y][mb_x])   Conceal_Error(inY, mb_y, mb_x, refY, s_map);
  }
}

/*! 
 *************************************************************************************
 * \brief
 *    Copies a certain MB (mb_y,mb_x) of the frame inY[][] from the previous frame.
 *    For the time there is no better EC...
 *************************************************************************************
 */
void Conceal_Error(byte **inY, int mb_y, int mb_x, byte ***refY, byte **s_map)
{
  int i,j,block_x, block_y;
  int ref_inx = (IMG_NUMBER-1)%img->num_reference_frames;
  int pos_y = mb_y*MB_BLOCK_SIZE, pos_x = mb_x*MB_BLOCK_SIZE;
  int mv[2][BLOCK_MULTIPLE][BLOCK_MULTIPLE];
  int resY[MB_BLOCK_SIZE][MB_BLOCK_SIZE];
  int copy  = (decs->dec_mb_mode[mb_x][mb_y]==0 && (img->type==P_SLICE || (img->type==B_SLICE && img->nal_reference_idc>0)));
  int inter = (((decs->dec_mb_mode[mb_x][mb_y]>=1 && decs->dec_mb_mode[mb_x][mb_y]<=3) || decs->dec_mb_mode[mb_x][mb_y]==P8x8) && (img->type==P_SLICE || (img->type==B_SLICE && img->nal_reference_idc>0)));
  int ***tmp_mv = enc_picture->mv[LIST_0];
  
  switch(s_map[mb_y][mb_x])
  {
  case 1: //! whole slice lost (at least partition A lost)
    if (img->type!=I_SLICE)
    {
      for (j=0;j<MB_BLOCK_SIZE;j++)
        for (i=0;i<MB_BLOCK_SIZE;i++)
          inY[pos_y+j][pos_x+i] = refY[ref_inx][pos_y+j][pos_x+i];
    }
    else
    {
      for (j=0;j<MB_BLOCK_SIZE;j++)
        for (i=0;i<MB_BLOCK_SIZE;i++)
          inY[pos_y+j][pos_x+i] = 127;
    }
    break;
  case 5: //! partition B and partition C lost
    
    //! Copy motion vectors 
    for (block_y=0; block_y<BLOCK_MULTIPLE; block_y++)
      for (block_x=0; block_x<BLOCK_MULTIPLE; block_x++)
        for (i=0;i<2;i++)
          mv[i][block_y][block_x]=tmp_mv[mb_x*BLOCK_SIZE+block_x+4][mb_y*BLOCK_SIZE+block_y][i];
    
    //! Residuum ist set to zero    
    for(i=0;i<MB_BLOCK_SIZE;i++)
      for(j=0;j<MB_BLOCK_SIZE;j++)
        resY[j][i]=0;
    
    //! not first frame
    if (img->type!=I_SLICE)
    {
      //! if copy mb
      if (copy)
      {
        for (j=0;j<MB_BLOCK_SIZE;j++)
          for (i=0;i<MB_BLOCK_SIZE;i++)
            inY[pos_y+j][pos_x+i] = refY[ref_inx][pos_y+j][pos_x+i];
      }
      //! if inter mb
      else if (inter)  
      {
        for (block_y = mb_y*BLOCK_SIZE ; block_y < (mb_y*BLOCK_SIZE + BLOCK_MULTIPLE) ; block_y++)
          for (block_x = mb_x*BLOCK_SIZE ; block_x < (mb_x*BLOCK_SIZE + BLOCK_MULTIPLE) ; block_x++)
          {
            Get_Reference_Block(refY[ref_inx],
                                block_y, block_x,
                                mv[0][block_y - mb_y*BLOCK_SIZE][block_x - mb_x*BLOCK_SIZE],
                                mv[1][block_y - mb_y*BLOCK_SIZE][block_x - mb_x*BLOCK_SIZE],
                                decs->RefBlock);
            for (j=0;j<BLOCK_SIZE;j++)
              for (i=0;i<BLOCK_SIZE;i++)
              {
                inY[block_y*BLOCK_SIZE + j][block_x*BLOCK_SIZE + i] = decs->RefBlock[j][i];
              }
          }
      }
      else //intra; up to now only copy mb, may integrate nokia EC 
      {
        for (j=0;j<MB_BLOCK_SIZE;j++)
          for (i=0;i<MB_BLOCK_SIZE;i++)
            inY[pos_y+j][pos_x+i] = refY[ref_inx][pos_y+j][pos_x+i];
      }
    }
    else //! first frame; up to now set value to grey, may integrate nokia EC 
    {
      for (j=0;j<MB_BLOCK_SIZE;j++)
        for (i=0;i<MB_BLOCK_SIZE;i++)
          inY[pos_y+j][pos_x+i] = 127;
    }
    break;
  case 3: //! Partition C lost
    if(img->type!=I_SLICE)
    {
      //! Copy motion vectors 
      for (block_y=0; block_y<BLOCK_MULTIPLE; block_y++)
        for (block_x=0; block_x<BLOCK_MULTIPLE; block_x++)
          for (i=0;i<2;i++)
            mv[i][block_y][block_x]=tmp_mv[mb_x*BLOCK_SIZE+block_x+4][mb_y*BLOCK_SIZE+block_y][i];
    
      //! Residuum ist set to zero    
      for(i=0;i<MB_BLOCK_SIZE;i++)
        for(j=0;j<MB_BLOCK_SIZE;j++)
          resY[j][i]=0;

      //! if copy mb
      if (copy)
      {
        for (j=0;j<MB_BLOCK_SIZE;j++)
          for (i=0;i<MB_BLOCK_SIZE;i++)
            inY[pos_y+j][pos_x+i] = refY[ref_inx][pos_y+j][pos_x+i];
      }
      //! if inter mb
      else if (inter)  
      {
        for (block_y = mb_y*BLOCK_SIZE ; block_y < (mb_y*BLOCK_SIZE + BLOCK_MULTIPLE) ; block_y++)
          for (block_x = mb_x*BLOCK_SIZE ; block_x < (mb_x*BLOCK_SIZE + BLOCK_MULTIPLE) ; block_x++)
            {
              Get_Reference_Block(refY[ref_inx],
                                  block_y, block_x,
                                  mv[0][block_y - mb_y*BLOCK_SIZE][block_x - mb_x*BLOCK_SIZE],
                                  mv[1][block_y - mb_y*BLOCK_SIZE][block_x - mb_x*BLOCK_SIZE],
                                  decs->RefBlock);
              for (j=0;j<BLOCK_SIZE;j++)
                for (i=0;i<BLOCK_SIZE;i++)
                {
                  inY[block_y*BLOCK_SIZE + j][block_x*BLOCK_SIZE + i] = decs->RefBlock[j][i];
                }
            }
      }
    }
    break;
  case 2: //! Partition B lost
    if(img->type!=I_SLICE)
    {
      if(!inter)
      {
        for (j=0;j<MB_BLOCK_SIZE;j++)
          for (i=0;i<MB_BLOCK_SIZE;i++)
            inY[pos_y+j][pos_x+i] = refY[ref_inx][pos_y+j][pos_x+i];
      }
    }
    else //! first frame; up to now set value to grey, may integrate nokia EC 
    {
      for (j=0;j<MB_BLOCK_SIZE;j++)
        for (i=0;i<MB_BLOCK_SIZE;i++)
          inY[pos_y+j][pos_x+i] = 127;
    }
    break;
  } //! End Switch
}