A method for decoding video data in accordance with High Efficiency Video Coding, HEVC, by using a coded picture buffer, CPB, operating at a sub-picture level, the method comprising: receiving, by a video decoder, a bitstream that comprises a series of Network Abstraction Layer, NAL, units, the series of NAL units including a non-Video-Coding-Layer, non-VCL, NAL unit; if the non-VCL NAL unit has a nal_unit_type that is equal to UNSPECO, or is equal to FD_NUT, or is equal to EOS_NUT, or is equal to EOB_NUT, or is in the range of RSV_NVCL44 to RSV_NVCL47, or is in the range of UNSPEC48 to UNSPEC63, associating, by the video decoder, the non-VCL NAL unit with a most recent VCL NAL unit preceding the non-VCL NAL unit in decoding order, wherein otherwise the non-VCL NAL unit is associated with the first subsequent VCL NAL unit in decoding order; decoding a duration between a CPB removal time of a first decoding unit (110, 112), DU, in an access unit and a CPB removal time of a second DU, wherein the first DU consists of one or more VCL NAL units and all non-VCL NAL units associated with the one or more VCL NAL units, the one or more VCL NAL units and all non-VCL NAL units associated with the one or more VCL NAL units being in the series of NAL units; and determining a CPB removal time of the first DU based at least in part on the decoded duration; and at the determined CPB removal time of the first DU, removing, by the video decoder, video data associated with the first DU from the CPB and decoding the video data associated with the first DU, wherein the video data associated with the first DU that is removed from the CPB and decoded at the CPB removal time of the first DU includes the non-VCL NAL unit having a nal_unit_type that is equal to UNSPECO, or is equal to FD_NUT, or is equal to EOS_NUT or EOB_NUT, or is in the range of RSV_NVCL44 to RSV_NVCL47 or is in the range of UNSPEC48 to UNSPEC63. receiving, by a video decoder, a bitstream that comprises a series of Network Abstraction Layer, NAL, units, the series of NAL units including a non-Video-Coding-Layer, non-VCL, NAL unit; if the non-VCL NAL unit has a nal_unit_type that is equal to UNSPECO, or is equal to FD_NUT, or is equal to EOS_NUT, or is equal to EOB_NUT, or is in the range of RSV_NVCL44 to RSV_NVCL47, or is in the range of UNSPEC48 to UNSPEC63, associating, by the video decoder, the non-VCL NAL unit with a most recent VCL NAL unit preceding the non-VCL NAL unit in decoding order, wherein otherwise the non-VCL NAL unit is associated with the first subsequent VCL NAL unit in decoding order; decoding a duration between a CPB removal time of a first decoding unit (110, 112), DU, in an access unit and a CPB removal time of a second DU, wherein the first DU consists of one or more VCL NAL units and all non-VCL NAL units associated with the one or more VCL NAL units, the one or more VCL NAL units and all non-VCL NAL units associated with the one or more VCL NAL units being in the series of NAL units; and determining a CPB removal time of the first DU based at least in part on the decoded duration; and at the determined CPB removal time of the first DU, removing, by the video decoder, video data associated with the first DU from the CPB and decoding the video data associated with the first DU, wherein the video data associated with the first DU that is removed from the CPB and decoded at the CPB removal time of the first DU includes the non-VCL NAL unit having a nal_unit_type that is equal to UNSPECO, or is equal to FD_NUT, or is equal to EOS_NUT or EOB_NUT, or is in the range of RSV_NVCL44 to RSV_NVCL47 or is in the range of UNSPEC48 to UNSPEC63.