In an example, a method for video coding includes processing a Supplemental Enhancement Information (SEI) Network Abstraction Layer (NAL) unit that comprises one or more SEI message structures in a raw byte sequence payload (RBSP), such that one or more SEI message structure includes at least one nesting SEI message structure having one or more SEI messages. In various embodiments, the SEI NAL unit is processed, and a syntax element, indicative of a number of SEI messages comprised within the at least one nesting message structure, is coded.