SCTE-35
SCTE-35 is a broadcast standard for placing cue markers inside a video stream that signal where ad breaks and program changes start and end. The markers travel with the video, for example in MPEG-TS or as tags in an HLS playlist. Downstream systems read them to know exactly when to swap in an ad or a local program.
Why it matters
SCTE-35 is how ad breaks become sellable in live and linear video. Without accurate markers, ads cut into the middle of a scene or are skipped entirely, which loses revenue and frustrates viewers. Most FAST platforms and ad systems expect these markers.
How it works
- The broadcaster or playout system marks the start and end of each ad break or program change.
- These cue messages are embedded in the stream, for example in MPEG-TS or as HLS playlist tags.
- A downstream system, such as an ad insertion server, reads the markers as the stream passes.
- At each marked break, the system swaps in an ad or local program for the exact duration.
What is an SCTE-35 marker used for?
An SCTE-35 marker tells downstream systems exactly where an ad break or program change starts and ends. Ad insertion servers use markers to replace breaks with targeted ads. Other systems use them to switch to local content, blackout events or trigger recording.
How does SCTE-35 work with HLS?
In HLS, SCTE-35 markers are carried as tags in the playlist, so players and ad servers can see where breaks fall. Common forms include date-range tags or cue-out and cue-in tags. Server-side ad insertion systems read these tags and stitch ad segments into the playlist for each viewer.
Where it's used
OTT services and sports broadcasters use SCTE-35 markers so ad systems know where breaks start and end in linear and FAST channels. Ad-free on-demand services rarely need them.
Where it usually goes wrong, and how FastPix handles it
Teams building linear or FAST channels from an on-demand library often have no break markers in their content, so downstream ad systems cannot tell where ads belong.
Channels scheduled in FastPix Cloud Playout can carry SCTE-35 markers, whether the lineup is on-demand titles, live events or both. A channel built from an on-demand library arrives with breaks that ad systems and FAST platforms can fill and sell.
By the numbers
- SCTE-35's full name is Digital Program Insertion Cueing Message for Cable, and it is a joint ANSI and Society of Cable Telecommunications Engineers standard, with a 2019 edition. (SCTE-35 (Wikipedia))
