itional_extension2_flag shall be equal to 0 in bitstreams conforming to this Recommendation | International Standard. The value of 1 for additional_extension2_flag is reserved for future use by ITU-T |ISO/IEC. Decoders shall ignore all data that follow the value 1 for _extension2_flag in a subset sequence parameter set NAL unit. additional_extension2_data_flag may have any value. It shall not affect the conformance to profiles specified in Annex A, G, or H. 7.4.2.2 Picture parameter set RBSP semantics pic_parameter_set_id identifies the picture parameter set that is referred to in the slice header. The value of pic_parameter_set_id shall be in the range of 0 to 255, inclusive. seq_parameter_set_i id refers to the active sequence parameter set. The value of seq_parameter_set_id id shall be in the range of 0 to 31, inclusive. Rec. ITU-T H.264 (01/2012) entropy_coding_mode_flag selects the entropy decoding method to be applied for the syntax elements for which two descriptors appear in the syntax tables as follows: If entropy_coding_mode_flag is equal to 0, the method specified by the left descriptor in the syntax table is applied (Exp-Golomb coded, see clause 9.1 or CAVLC, see clause 9.2). Otherwise (entropy_coding_mode_flag is equal to 1), the method specified by the right descriptor in the syntax table is applied (CABAC, see clause 9.3). ottom_field_pic_order_in_frame_present_flag equal to 1 specifies that the syntax elements delta_pic_order_cnt_bottom (when pic_order_cnt_type is equal to 0) or delta_pic_order_cnt[1] (when pic_order_cnt_type is equal to 1), which are related to picture order counts for the bottom field of a coded frame, are present in the slice headers for coded frames as specified in clause 7.3.3.bottom_field_pic_order_in_frame_present_flag equal to 0 specifies that the syntax elements delta_pic_order_cnt_bottor delta_pic_order_cnt[1]are not present in the slice headers. num_slice_groups_minus1 plus 1 specifies the number of slice groups for a picture. When num_slice_groups_minus1 is equal to 0,