/*! *********************************************************************** * \brief按照螺旋搜索顺序进行全搜索 *    Full pixel block motion search *    目标是得到(mv_x,mv_y)和min_mcost，(mv_x,mv_y)指示从哪里开始做分像素搜索，search center *    后者用来跟分像素搜索结果做比较 *********************************************************************** */int                                               //  ==> minimum motion cost after searchFullPelBlockMotionSearch (pel_t**   orig_pic,     // <--  original pixel values for the AxB block                          int       ref,          // <--  reference frame (0... or -1 (backward))                          int       list,                          int       pic_pix_x,    // <--  absolute x-coordinate of regarded AxB blockAxB宏块原点在图像中的绝对坐标                          int       pic_pix_y,    // <--  absolute y-coordinate of regarded AxB block                          int       blocktype,    // <--  block type (1-16x16 ... 7-4x4)                          int       pred_mv_x,    // <--  motion vector predictor (x) in sub-pel units                          int       pred_mv_y,    // <--  motion vector predictor (y) in sub-pel units                          int*      mv_x,         // <--> in: search center (x) / out: motion vector (x) - in pel units                          int*      mv_y,         // <--> in: search center (y) / out: motion vector (y) - in pel units                          int       search_range, // <--  1-d search range in pel units                          int       min_mcost,    // <--  minimum motion cost (cost for center or huge value)                          double    lambda)       // <--  lagrangian parameter for determining motion cost{  int   pos, cand_x, cand_y, y, x4, mcost;    pel_t *orig_line, *ref_line;  pel_t *(*get_ref_line)(int, pel_t*, int, int, int, int);////参考帧偏移量 帧场自适应且宏块地址为偶数=4 帧场自适应宏块地址为奇数=2 非帧场自适应=0  int   list_offset   = ((img->MbaffFrameFlag)&&(img->mb_data[img->current_mb_nr].mb_field))? img->current_mb_nr%2 ? 4 : 2 : 0;  pel_t *ref_pic            = listX[list+list_offset][ref]->imgY_11;  int   img_width     = listX[list+list_offset][ref]->size_x;  int   img_height    = listX[list+list_offset][ref]->size_y;  int   best_pos      = 0;                                        // position with minimum motion cost  //计算最大需要搜索的位置个数  int   max_pos       = (2*search_range+1)*(2*search_range+1);    // number of search positions  int   lambda_factor = LAMBDA_FACTOR (lambda);                   // factor for determining lagragian motion cost  int   blocksize_y   = input->blc_size[blocktype][1];            // vertical block size  int   blocksize_x   = input->blc_size[blocktype][0];            // horizontal block size  int   blocksize_x4  = blocksize_x >> 2;                         // horizontal block size in 4-pel units  int   pred_x        = (pic_pix_x << 2) + pred_mv_x;       // predicted position x (in sub-pel units)1/4子像素为单位的预测MV  int   pred_y        = (pic_pix_y << 2) + pred_mv_y;       // predicted position y (in sub-pel units)  int   center_x      = pic_pix_x + *mv_x;                        // center position x (in pel units)  int   center_y      = pic_pix_y + *mv_y;                        // center position y (in pel units)  int   check_for_00  = (blocktype==1 && !input->rdopt && img->type!=B_SLICE && ref==0);  //===== set function for getting reference picture lines =====  //通过判断搜索范围会不会出界，设置获取参考像素值的函数  if ((center_x > search_range) && (center_x < img->width -1-search_range-blocksize_x) &&      (center_y > search_range) && (center_y < img->height-1-search_range-blocksize_y)   )  {     get_ref_line = FastLineX;//未出界  }  else  {     get_ref_line = UMVLineX;//出界  }  //===== loop over all search positions =====  //max_pos是搜索位置的个数,计算见上面  for (pos=0; pos<max_pos; pos++)  {    //--- set candidate position (absolute position in pel units) ---    /*(center_x,center_y)是由预测MV估计出来的搜索中心，在以它为中心的范围内，    对按照螺旋形顺序排列的候选点进行搜索，    每个候选点都是一个可能参考块的左上角起始点  */    cand_x = center_x + spiral_search_x[pos];//螺旋搜索    cand_y = center_y + spiral_search_y[pos];    //--- initialize motion cost (cost for motion vector) and check ---    //计算MVD的代价，换算成四分之一像素(cand--candidate候选点)    mcost = MV_COST (lambda_factor, 2, cand_x, cand_y, pred_x, pred_y);    if (check_for_00 && cand_x==pic_pix_x && cand_y==pic_pix_y)    {//螺旋搜索到的点为原点,不过为什么是减去16bit?      mcost -= WEIGHTED_COST (lambda_factor, 16);    }    //如果只是MV的代价就已经大于现有的最小代价就舍弃    if (mcost >= min_mcost)   continue;    //--- add residual cost to motion cost ---    //blocksize_y blocksize_x4 是分块大小16x16 16x8 8x16......    for (y=0; y<blocksize_y; y++)     {      //(cand_x,cand_y+y)是一行的起始坐标，y++ 遍历每一行      ref_line  = get_ref_line (blocksize_x, ref_pic, cand_y+y, cand_x, img_height, img_width);      orig_line = orig_pic [y];      //计算当前帧和参考帧的像素残差      for (x4=0; x4<blocksize_x4; x4++) //以4个为一组计算      {        mcost += byte_abs[ *orig_line++ - *ref_line++ ];        mcost += byte_abs[ *orig_line++ - *ref_line++ ];        mcost += byte_abs[ *orig_line++ - *ref_line++ ];        mcost += byte_abs[ *orig_line++ - *ref_line++ ];      }      if (mcost >= min_mcost)  //如果已经比最小代价大，就没必要计算下面的行了      {        break;      }    }        //--- check if motion cost is less than minimum cost ---    //记录下最小代价和最佳匹配位置    if (mcost < min_mcost)    {      best_pos  = pos;      min_mcost = mcost;    }  }  //===== set best motion vector and return minimum motion cost =====  if (best_pos)  {    *mv_x += spiral_search_x[best_pos];  //因为螺旋搜索数组中记录的是该位置的点    *mv_y += spiral_search_y[best_pos];  //与(center_x,center_y)的差  }  return min_mcost;  //返回最小代价}

//螺旋搜索（全搜索）位置初始化 for (k=1, l=1; l<=max(1,search_range); l++)  {    for (i=-l+1; i< l; i++)    {      spiral_search_x[k] =  i;  spiral_search_y[k++] = -l;      spiral_search_x[k] =  i;  spiral_search_y[k++] =  l;      /*       *                                        *                         9  3 5 7 10       *          1 0 2          11 1 0 2 12       *                         13 4 6 8 14       *        */    }    for (i=-l;   i<=l; i++)    {      spiral_search_x[k] = -l;  spiral_search_y[k++] =  i;      spiral_search_x[k] =  l;  spiral_search_y[k++] =  i;      /*                             15 17 19  21 23       *         3 5 7                9  3  5  7  10       *         1 0 2               11  1  0  2  12       *         4 6 8               13  4  6  8  14       *                             16 18 20 22  24        */     }  }

/*! *********************************************************************** * \brief快速正像素搜索 *    Fast Full pixel block motion search *    目标是得到(mv_x,mv_y)和min_mcost，(mv_x,mv_y)指示从哪里开始做分像素搜索，search center *    后者用来跟分像素搜索结果做比较 *********************************************************************** */int                                                   //  ==> minimum motion cost after searchFastFullPelBlockMotionSearch (pel_t**   orig_pic,     // <--  not used                              int       ref,          // <--  reference frame (0... or -1 (backward))                              int       list,                              int       pic_pix_x,    // <--  absolute x-coordinate of regarded AxB block                              int       pic_pix_y,    // <--  absolute y-coordinate of regarded AxB block                              int       blocktype,    // <--  block type (1-16x16 ... 7-4x4)                              int       pred_mv_x,    // <--  motion vector predictor (x) in sub-pel units                              int       pred_mv_y,    // <--  motion vector predictor (y) in sub-pel units                              int*      mv_x,         //  --> motion vector (x) - in pel units                              int*      mv_y,         //  --> motion vector (y) - in pel units                              int       search_range, // <--  1-d search range in pel units                              int       min_mcost,    // <--  minimum motion cost (cost for center or huge value)                              double    lambda)       // <--  lagrangian parameter for determining motion cost{  int   pos, offset_x, offset_y, cand_x, cand_y, mcost;  int   max_pos       = (2*search_range+1)*(2*search_range+1);              // number of search positions  int   lambda_factor = LAMBDA_FACTOR (lambda);                             // factor for determining lagragian motion cost  int   best_pos      = 0;                                                  // position with minimum motion cost  int   block_index;                                                        // block index for indexing SAD array  int*  block_sad;                                                          // pointer to SAD array  block_index   = (pic_pix_y-img->opix_y)+((pic_pix_x-img->opix_x)>>2); // block index for indexing SAD array  block_sad     = BlockSAD[list][ref][blocktype][block_index];         // pointer to SAD array  //===== set up fast full integer search if needed / set search center =====  if (!search_setup_done[list][ref])//对一个参考帧只做一次  {    //计算搜索范围所有位置所有分块模式的SAD(整像素)    SetupFastFullPelSearch (ref, list);  }  offset_x = search_center_x[list][ref] - img->opix_x; //搜索中心相对原宏块的偏移  offset_y = search_center_y[list][ref] - img->opix_y;  //===== cost for (0,0)-vector: it is done before, because MVCost can be negative =====  //原点(这里的原点都是是当前块所在的位置)  if (!input->rdopt)  {    //把刚才计算的SAD 跟mv代价相加得到总代价    mcost = block_sad[pos_00[list][ref]] + MV_COST (lambda_factor, 2, 0, 0, pred_mv_x, pred_mv_y);    if (mcost < min_mcost)    {      min_mcost = mcost;      best_pos  = pos_00[list][ref];//每帧搜索中心的位置    }  }  //===== loop over all search positions =====  for (pos=0; pos<max_pos; pos++, block_sad++)  {    //--- check residual cost ---    if (*block_sad < min_mcost)    {      //--- get motion vector cost ---      //计算出搜索位置，按照螺旋形顺序spiral_search_xy      cand_x = offset_x + spiral_search_x[pos];      cand_y = offset_y + spiral_search_y[pos];      mcost  = *block_sad;//在SetupFastFullPelSearch已经做好      mcost += MV_COST (lambda_factor, 2, cand_x, cand_y, pred_mv_x, pred_mv_y);    //计算 MV 代价      //--- check motion cost ---      if (mcost < min_mcost)      {        min_mcost = mcost;        best_pos  = pos;      }    }  }  //===== set best motion vector and return minimum motion cost =====  *mv_x = offset_x + spiral_search_x[best_pos];//根据代价最小，计算出最佳MV  *mv_y = offset_y + spiral_search_y[best_pos];  return min_mcost;}

/*如果参考块超出参考帧边界，用边界值进行填充*/pel_t *UMVLineX (int size, pel_t* Pic, int y, int x, int height, int width){  int i, maxx;  pel_t *Picy;  Picy = Pic + max(0,min(height-1,y)) * width;  //先把y范围限制在(0,height-1)内  if (x < 0)                            // Left edge  {    maxx = min(0,x+size);   //搜索范围可以大于16的，所以x+16是可以小于0的    for (i = x; i < maxx; i++)  //把出界的部分都赋值为边界上的值，一画图就理解了    {      line[i-x] = Picy [0];             // Replicate left edge pixel    }    maxx = x+size;                         //把没出界的像素也拷贝到line数组中        for (i = 0; i < maxx; i++)          // Copy non-edge pixels      line[i-x] = Picy [i];  }  else if (x > width-size)         // Right edge  同理  {    maxx = width;    for (i = x; i < maxx; i++)    {      line[i-x] = Picy [i];             // Copy non-edge pixels    }    maxx = x+size;    for (i = max(width,x); i < maxx; i++)    {      line[i-x] = Picy [width-1];  // Replicate right edge pixel    }  }  else                                  // No edge  ，则返回y行x列的地址  {    return Picy + x;  }  return line;    //否则，返回line数组的地址}