S4M - Anchor Ends

Here is an interesting facet of the S4M system in use by certain broadcasters I would like to detail below.

Playlists
S4M can write playlists in a format known as H-class, which is a XML format listing events as “dlevent” XML nodes. Each event node contains a start time which is stored as the value of the “dlstart” child node. In addition, the total duration of which the event runs is stored as the “dlduration_hmsf” child node.

Events
There are 2 main classes of events: primary and secondary. Primary usually refers to a program or commercial segment. Secondary events run in parallel to primary events, and can be voiceovers, snipes or commercial secondary events.

Anchor End
When writing H-class playlists, S4M sometimes writes secondary events that have a “dlstart” time that occurs after the primary event it is supposed to run within ends. This is a glitch with the S4M trafficking system but what this means is that the secondary event runs near the end of the primary event. The exact actual time the secondary event runs at can be determined by taking the difference of the primary event’s end time and the secondary event’s start time, and subtracting this offset from the primary event’s end time to determine the true “dlstart” time of this secondary event. To put this in the form of mathematical equations:

Primary event end time = primary event start time (dlstart) + primary event duration (dlduration_hmsf)

Now, determine if this secondary event is an anchor end or not:
If (Secondary event start time (dlstart) > Primary event end time) then
This is an anchor end.

Offset = Secondary event start time (dlstart) – Primary event end time
Secondary event offset time = Primary event end time – Offset (calculated above)