s not containing any NAL units with nal_unit_type equal to 0, 7, 8, or in the range of 12 to 18, inclusive, or in the range of 20 to 31, inclusive, is shown in Figure 7-1. Rec. ITU-T H.264 (01/2012) start Access unit delimiter Primary coded picture Redundant coded picture Auxiliary coded picture End of sequence End of stream H.264(09)_F7-1 Figure 7-1 - Structure of an access unit not containing any NAL units with nal_unit_type equal to 0, 7, 8, or in the range of 12 to 18, inclusive, or in the range of 20 to 31, inclusive 7.4.1.2.4 Detection of the first VCL NAL unit of a primary coded picture This clause specifies constraints on VCL NAL unit syntax that are sufficient to enable the detection of the first VCL NAL unit of each primary coded picture for coded video sequences that conform to one or more of the profiles specified in Annex A and are decoded using the decoding process specified in clauses 2-9. Any coded slice NAL unit or coded slice data partition A NAL unit of the primary coded picture of the current access unit shall be different from any coded slice NAL unit or coded slice data partition A NAL unit of the primary coded picture of the previous access unit in one or more of the following ways: frame num differs in value. The value of frame num used to test this condition is the value of frame num that appears in the syntax of the slice header, regardless of whether that value is inferred to have been equal to 0 for subsequent use in the decoding process due to the presence of memory_management_control_operation equal to 5. NOTE 1 - A consequence of the above statement is that a primary coded picture having frame num equal to 1 cannot contain a memory_management_control_operation equal to 5 unless some other condition listed below is fulfilled for the next primary coded picture that follows after it (if any). pic_parameter_: set id differs in value. field_pic_flag differs in value. bottom_field_flag is present in both and differs in value. nal ref idc differs in value with one of the nal ref idc values