The delta_pic_order_cnt_bottom is used in Type0 POC calculation to calculated BottomFieldOrderCnt as:
BottomFieldOrderCnt = TopFieldOrderCnt + delta_pic_order_cnt_bottom
This changes the FieldAbsolute variant to expose the fields more explicitly as pic_order_cnt_lsb and delta_pic_order_cnt_bottom make it clearer for the user how the values should fit into the calculations.
The delta_pic_order_cnt_bottom is used in Type0 POC calculation to calculated BottomFieldOrderCnt as: BottomFieldOrderCnt = TopFieldOrderCnt + delta_pic_order_cnt_bottom
This changes the FieldAbsolute variant to expose the fields more explicitly as pic_order_cnt_lsb and delta_pic_order_cnt_bottom make it clearer for the user how the values should fit into the calculations.