SCTE 104/35 Codex

Every multiple_operation_message carries a timestamp() that says when to process its operations. Its time_type chooses the trigger: 0 for immediate, where processing is timed to the start of the video frame that contains the last received byte (clause 8.2.3.1) rather than to the byte itself, 1 for a UTC time, 2 for a SMPTE VITC time code, or 3 for a GPI contact closure. In GPI mode the message names a GPI_number and the GPI_edge to watch, and when that physical input transitions, the Injector processes the waiting operations. This lets an automation system either schedule a message for a precise time or arm it to fire off an external hardware trigger. In the 2004-2014 editions timestamp() is clause 11.5 rather than 12.5.