ange of 0 to 255, inclusive. sub_seq_id identifies the sub-sequence within a layer. When the current picture resides in a sub-sequence for which the first picture in decoding order is an IDR picture, the value of sub_seq_id shall be the same as the value of idr_pic_id of the IDR picture. sub_seq_id shall be in the range of 0 to 65535, inclusive. first_ref_pic_flag equal to 1 specifies that the current picture is the first reference picture of the sub-sequence in decoding order. When the current picture is not the first picture of the sub-sequence in decoding order, the first_ref_pic_flag shall be equal to 0. leading_non_ref_pic_flag equal to 1 specifies that the current picture is a non-reference picture preceding any reference picture in decoding order within the sub-sequence or that the sub-sequence contains no reference pictures. When the current picture is a reference picture or the current picture is a non-reference picture succeeding at least one reference picture in decoding order within the sub-sequence, the leading_non_ref_pic_flag shall be equal to 0. last_pic_flag equal to 1 indicates that the current picture is the last picture of the sub-sequence (in decoding order), including all reference and non-reference pictures of the sub-sequence. When the current picture is not the last picture of the sub-sequence (in decoding order), last_pic_flag shall be equal to 0. The current picture is assigned to a sub-sequence as follows: If one or more of the following conditions is true, the current picture is the first picture of a sub-sequence in decoding order: no earlier picture in decoding order is labelled with the same values of sub_seq_id and sub_seq_layer_num as the current picture, the value of leading_non_ref_pic_flag is equal to 1 and the value of leading_non_ref_pic_flagi is equal to 0 in the previous picture in decoding order having the same values of sub_seq_id and sub_seq_layer_num as the current picture, the value of first ref_pic_flag is equal to 1 and the value of leading_non_ref_pic_flag is equal