SCTE 104/35 Codex

SCTE 104 carries two message shapes. A single_operation_message holds exactly one Basic Request or Basic Response, such as an init or an alive heartbeat, and it is the form every response takes. A multiple_operation_message is the workhorse for message generation: it carries a timestamp() and a data() loop of one or more operations, so a whole splice with its descriptors travels as a single unit. The first two bytes tell them apart, since a multiple_operation_message always begins with 0xFFFF in its Reserved field. In the 2004-2014 editions the message formats are clause 7 rather than clause 8.