icture timing SEI messages, by some means not specified in this Recommendation | International Standard. When vcl_hrd_parameters_present_flag is equal to 1, VCL HRD parameters (clauses E.1.2 and E.2.2) immediately follow the flag. Rec. ITU-T H.264 (01/2012) The variable VclHrdBpPresentFlag is derived as follows: If any of the following is true, the value of VclHrdBpPresentFlag shall be set equal to 1: ycl_hrd_parameters_present_flag is present in the bitstream and is equal to 1, the need for presence of buffering periods for VCL HRD operation to be present in the bitstream in buffering period SEI messages is determined by the application, by some means not specified in this Recommendation International Standard. Otherwise, the value of VclHrdBpPresentFlag shall be set equal to 0. The variable CpbDpbDelaysPresentFlag is derived as follows: If any of the following is true, the value of CpbDpbDelaysPresentFlag shall be set equal to 1: nal_hrd_parameters_present_flag is present in the bitstream and is equal to 1, ycl_hrd_parameters_present_flag: is present in the bitstream and is equal to 1, the need for presence of CPB and DPB output delays to be present in the bitstream in picture timing SEI messages is determined by the application, by some means not specified in this Recommendation International Standard. Otherwise, the value of CpbDpbDelaysPresentFlag shall be set equal to 0. low_delay_hrd_flag specifies the HRD operational mode as specified in Annex C. When fixed_frame_rate_flag is equal to 1, __delay_hrd_flag shall be equal to 0. When low_delay_hrd_flag is not present, its value shall be inferred to be equal to 1 - fixed_frame_rate_flag. NOTE 10 - When low_delay_hrd_flag is equal to 1, "big pictures" that violate the nominal CPB removal times due to the number of bits used by an access unit are permitted. It is expected, but not required, that such "big pictures" occur only occasionally. pic_struct_present_flag equal to 1 specifies that picture timing SEI messages (clause D.2.2) are present that include the pi