A method of decoding video data, the method comprising: decoding a value of a type of network abstraction layer unit, NAL, for a supplementary enhancement information NAL unit, SEI, of a bit stream, in that the NAL unit type value for the SEI NAL unit indicates whether the NAL unit comprises a prefix SEI NAL unit, which includes a prefix SEI message, or a SEI NAL unit of suffix, which includes a suffix SEI message; and decode bitstream video data based on whether the SEI NAL unit is a prefix SEI NAL unit, in which the prefix SEI NAL units cannot follow a last NAL unit of the video coding layer, VCL, in an access unit in decoding order, or if the SEI NAL unit is a suffix SEI NAL unit, in which the suffix SEI NAL units can follow to the last VCL NAL unit in an access unit in order of decoding, and shall not precede a first VCL NAL unit in the access unit in decoding order, and based on the data of the unit of NAL of SEI.