JM解码(一)：参考帧列表和DPB处理

以P帧为例：

void alloc_ref_pic_list_reordering_buffer(Slice *currSlice)
{
   int size = currSlice->num_ref_idx_active[LIST_0] + 1;
   if ((currSlice->modification_of_pic_nums_idc[LIST_0] = calloc(size ,sizeof(int)))==NULL) 
      no_mem_exit("alloc_ref_pic_list_reordering_buffer: modification_of_pic_nums_idc_l0");
   if ((currSlice->abs_diff_pic_num_minus1[LIST_0] = calloc(size,sizeof(int)))==NULL) 
      no_mem_exit("alloc_ref_pic_list_reordering_buffer: abs_diff_pic_num_minus1_l0");
   if ((currSlice->long_term_pic_idx[LIST_0] = calloc(size,sizeof(int)))==NULL) 
      no_mem_exit("alloc_ref_pic_list_reordering_buffer: long_term_pic_idx_l0");
   if ((currSlice->abs_diff_view_idx_minus1[LIST_0] = calloc(size,sizeof(int)))==NULL) 
      no_mem_exit("alloc_ref_pic_list_reordering_buffer: abs_diff_view_idx_minus1_l0");

   currSlice->modification_of_pic_nums_idc[LIST_1] = NULL;
   currSlice->abs_diff_pic_num_minus1[LIST_1] = NULL;
   currSlice->long_term_pic_idx[LIST_1] = NULL;
   currSlice->abs_diff_view_idx_minus1[LIST_1] = NULL;
}

num_ref_idx_active： 表示当前帧有几个参考帧
modification_of_pic_nums_idc：传输帧改变的方式：0，1，2分别是 短期的加 短期的减 长期
abs_diff_pic_num_minus1： 短期参考帧，传输和当前帧差值
long_term_pic_idx： 长期参考帧，传输POC

static void ref_pic_list_reordering(Slice *currSlice)
{
  //VideoParameters *p_Vid = currSlice->p_Vid;
  byte dP_nr = assignSE2partition[currSlice->dp_mode][SE_HEADER];
  DataPartition *partition = &(currSlice->partArr[dP_nr]);
  Bitstream *currStream = partition->bitstream;
  int i, val;

  alloc_ref_pic_list_reordering_buffer(currSlice);
  // 根据 num_ref_idx_active 分配内存空间
  
  if (currSlice->slice_type != I_SLICE && currSlice->slice_type != SI_SLICE)
  {
    val = currSlice->ref_pic_list_reordering_flag[LIST_0] = read_u_1 ("SH: ref_pic_list_reordering_flag_l0", currStream, &p_Dec->UsedBits);
	
	// 调整 RefList0
    if (val)
    {
      i=0;
      do
      {
      	// 先读一个修改模式
      	// 0||1 是修改短期参考帧
      	// 2 是修改长期参考帧
      	// 紧接着就是修改内容
        val = currSlice->modification_of_pic_nums_idc[LIST_0][i] = read_ue_v("SH: modification_of_pic_nums_idc_l0", currStream, &p_Dec->UsedBits);
        if (val==0 || val==1)
        {
          // 短期参考帧的帧偏移
          currSlice->abs_diff_pic_num_minus1[LIST_0][i] = read_ue_v("SH: abs_diff_pic_num_minus1_l0", currStream, &p_Dec->UsedBits);
        }
        else
        {
          if (val==2)
          {
            // 长期参考帧的 idx
            currSlice->long_term_pic_idx[LIST_0][i] = read_ue_v("SH: long_term_pic_idx_l0", currStream, &p_Dec->UsedBits);
          }
        }
        i++;
        // assert (i>currSlice->num_ref_idx_active[LIST_0]);
      } while (val != 3);
      // 3 是列表调整的循环停止标志
    }
  }

  // set reference index of redundant slices.
  if(currSlice->redundant_pic_cnt && (currSlice->slice_type != I_SLICE) )
  {
    currSlice->redundant_slice_ref_idx = currSlice->abs_diff_pic_num_minus1[LIST_0][0] + 1;
  }
}

void dec_ref_pic_marking(VideoParameters *p_Vid, Bitstream *currStream, Slice *pSlice)
{
  int val;

  DecRefPicMarking_t *tmp_drpm,*tmp_drpm2;

  // free old buffer content
  while (pSlice->dec_ref_pic_marking_buffer)
  {
    tmp_drpm=pSlice->dec_ref_pic_marking_buffer;

    pSlice->dec_ref_pic_marking_buffer=tmp_drpm->Next;
    free (tmp_drpm);
  }

#if (MVC_EXTENSION_ENABLE)
  if ( pSlice->idr_flag || (pSlice->svc_extension_flag == 0 && pSlice->NaluHeaderMVCExt.non_idr_flag == 0) )
#else
  if (pSlice->idr_flag)
#endif
  {
    pSlice->no_output_of_prior_pics_flag = read_u_1("SH: no_output_of_prior_pics_flag", currStream, &p_Dec->UsedBits);
    p_Vid->no_output_of_prior_pics_flag = pSlice->no_output_of_prior_pics_flag;
    pSlice->long_term_reference_flag = read_u_1("SH: long_term_reference_flag", currStream, &p_Dec->UsedBits);
  }
  else
  {
    pSlice->adaptive_ref_pic_buffering_flag = read_u_1("SH: adaptive_ref_pic_buffering_flag", currStream, &p_Dec->UsedBits);
    if (pSlice->adaptive_ref_pic_buffering_flag)
    {
      // read Memory Management Control Operation
      do
      {
        tmp_drpm=(DecRefPicMarking_t*)calloc (1,sizeof (DecRefPicMarking_t));
        tmp_drpm->Next=NULL;

        val = tmp_drpm->memory_management_control_operation = read_ue_v("SH: memory_management_control_operation", currStream, &p_Dec->UsedBits);

        if ((val==1)||(val==3))
        {
          tmp_drpm->difference_of_pic_nums_minus1 = read_ue_v("SH: difference_of_pic_nums_minus1", currStream, &p_Dec->UsedBits);
        }
        if (val==2)
        {
          tmp_drpm->long_term_pic_num = read_ue_v("SH: long_term_pic_num", currStream, &p_Dec->UsedBits);
        }

        if ((val==3)||(val==6))
        {
          tmp_drpm->long_term_frame_idx = read_ue_v("SH: long_term_frame_idx", currStream, &p_Dec->UsedBits);
        }
        if (val==4)
        {
          tmp_drpm->max_long_term_frame_idx_plus1 = read_ue_v("SH: max_long_term_pic_idx_plus1", currStream, &p_Dec->UsedBits);
        }

        // add command
        if (pSlice->dec_ref_pic_marking_buffer==NULL)
        {
          pSlice->dec_ref_pic_marking_buffer=tmp_drpm;
        }
        else
        {
          tmp_drpm2=pSlice->dec_ref_pic_marking_buffer;
          while (tmp_drpm2->Next!=NULL) tmp_drpm2=tmp_drpm2->Next;
          tmp_drpm2->Next=tmp_drpm;
        }

      }
      while (val != 0);
    }
  }
}