associated slice group set of the sub-picture scalable layer SEI message. The access unit associated with the sub-picture scalable layer SEI message shall not contain any primary coded VCL NAL unit that has dependency id equal to depId and IdrPicFlag equal to 0. The set of access units consisting of the access unit associated with the sub-picture scalable layer SEI message and all succeeding access units in decoding order until, but excluding, the next access unit that contains any primary coded VCL NAL unit with dependency_id equal to depId and IdrPicFlag equal to 1 or that does not contain any primary coded VCL NAL units with IdrPicFlag equal to 0 (if present) or the end of the bitstream (otherwise) is referred to as the target access unit set. The sub-picture scalable layer SEI message applies to the target access unit set. NOTE - The set of primary coded pictures in the target access unit set for a sub-picture scalable layer SEI message is identical to the target picture set for the associated motion-constrained slice group set SEI message. Rec. ITU-T H.264 (01/2012) layer_id indicates, when the access unit containing the sub-picture scalable layer SEI message belongs to the target access unit set of a scalability information SEI message, the layer identifier of the sub-picture scalable layer to which the coded slice NAL units in the associated slice group set belong. The value of layer_id shall be in the range of 0 to 2047, inclusive. The access unit containing the sub-picture scalable layer SEI message may or may not belong to the target access unit set of a scalability information SEI message. When the access unit containing the sub-picture scalable layer SEI message belongs to the target access unit set of a scalability information SEI message, the corresponding scalability information SEI message may or may not contain information for a scalable layer i with layer identifier layer_id[ i ] equal to layer id. When the access unit containing the sub-picture scalable layer SEI message belongs to the target a