A method for decoding video data, the video data comprising at least one access unit, AU (100, 102), the at least one AU comprising at least two decoding units, DUs (112-1, 112-4), the method comprising: decoding a sequence level flag, the sequence level flag equal to 1 specifying that sub-picture level coded picture buffer, CPB, removal delay parameters are present in picture timing supplemental enhancement information, SEI, messages and no sub-picture timing SEI message is present, the sequence level flag equal to 0 specifying that sub-picture level CPB removal delay parameters are present in sub-picture timing SEI messages and the picture timing SEI messages do not include sub-picture level CPB removal delay parameters; if the sequence level flag is equal to 1, decoding a sub-picture level CPB removal delay parameter for a current DU in a current AU from a picture timing SEI message associated with the current DU; if the sequence level flag is equal to 0, decoding the sub-picture level CPB removal delay parameter for the current DU in the current AU from a sub-picture timing SEI message associated with the current DU; determining, based at least in part on the sub-picture level CPB removal delay parameter for the current DU, a CPB removal time of the current DU; and at the determined CPB removal time of the current DU, decoding video data associated with the current DU and removing the current DU from the CPB, wherein the sub-picture level CPB removal delay parameter specifies the duration in sub-picture clock ticks between removal from the CPB of the last DU in decoding order in the current AU and removal of the current DU, wherein, when the current DU is the last DU in decoding order in the current AU, the value of the sub-picture level CPB removal delay parameter must be equal to 0. decoding a sequence level flag, the sequence level flag equal to 1 specifying that sub-picture level coded picture buffer, CPB, removal delay parameters are present in picture timing supplemental enhancement information, SEI, messages and no sub-picture timing SEI message is present, the sequence level flag equal to 0 specifying that sub-picture level CPB removal delay parameters are present in sub-picture timing SEI messages and the picture timing SEI messages do not include sub-picture level CPB removal delay parameters; if the sequence level flag is equal to 1, decoding a sub-picture level CPB removal delay parameter for a current DU in a current AU from a picture timing SEI message associated with the current DU; if the sequence level flag is equal to 0, decoding the sub-picture level CPB removal delay parameter for the current DU in the current AU from a sub-picture timing SEI message associated with the current DU; determining, based at least in part on the sub-picture level CPB removal delay parameter for the current DU, a CPB removal time of the current DU; and at the determined CPB removal time of the current DU, decoding video data associated with the current DU and removing the current DU from the CPB, wherein the sub-picture level CPB removal delay parameter specifies the duration in sub-picture clock ticks between removal from the CPB of the last DU in decoding order in the current AU and removal of the current DU, wherein, when the current DU is the last DU in decoding order in the current AU, the value of the sub-picture level CPB removal delay parameter must be equal to 0.