SCTE 104/35 Codex

SCTE 35 messages are increasingly delivered inside adaptive streaming rather than raw MPEG-2 transport. The guidance is to preserve the message content through the conversion, align signals with media segment boundaries where practical (some packets, such as a repeated time_descriptor, can fall off a boundary), and carry the signaling on each delivery format. HLS commonly uses an EXT-X-DATERANGE tag, whose SCTE35 attributes carry the message as hexadecimal, while the older EXT-X-SCTE35 tag carries it as Base64; DASH carries it as an MPD EventStream or an inband emsg box. The byte-level SCTE 35 message stays authoritative; the streaming tags only map its timing onto the presentation timeline.