0, vcl_hrd_parameters_present_flag shall be equal to 0, and pic_struct_present_flag shall be equal to 0. The value of 1 for timing_info_present_flag, nal_hrd_parameters_present_flag, vcl_hrd_parameters_present_flag,andp pic_struct_present_flag for subset sequence parameter set RBSPs is reserved for future use by ITU-T | ISO/IEC. When timing_info_present_flag is equal to 1, decoders shall ignore the values of the directly following num_units_in_tick,time_scale,fixed_frame_rate_flag syntax elements. When nal_hrd_parameters_present_flagi is equal to 1, decoders shall ignore the value of the syntax elements in the directly following rd_parameters() syntax structure. When vcl_hrd_parameters_present_flag is equal to 1, decoders shall ignore the value of the syntax elements in the directly following ard_parameters() syntax structure. When the seq_parameter_set_data() syntax structure is present in a sequence parameter set RBSP and vui_parameters_present_flag is equal to 1, the values of timing_info_present_flag, num_units_in_tick, time scale, fixed_frame_rate_flag, nal_hrd_parameters_present_flag cl_hrd_parameters_present_flag, low_delay_hrd_flag, pic_struct_present_flag and the values of syntax elements included in the hrd parameters() syntax structures, when present, shall be such that the bitstream activating the sequence parameter set is conforming to one or more of the profiles specified in Annex A. max_num_ref_frames specifies the maximum number of short-term and long-term reference frames, complementary reference field pairs, and non-paired reference fields that may be used by the decoding process for inter prediction of any picture in the coded video sequence. max_num_ref_frames also determines the size of the sliding window operation as specified in clause G.8.2.4.2. The value of max_num_ref_frames shall be in the range of 0 to MaxDpbFrames (as specified in clause G.10), inclusive. The allowed range of values for pic_width_in_mbs_minus1, pic_height_in_map_units_minus1, and frame_mbs_only_flag is specified by co