How output locking works in AWS Elemental Live
When you use output locking Elemental Live locks outputs when an event first starts. Elemental Live also resynchronizes the output of an event when an event is running.
Output locking has these key requirements:
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All inputs must have a timecode in the source. You can't set up output locking in events that use the system clock.
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The events must be able to communicate with each other over multicast or unicast.
How the initial lock occurs
When you start or restart all of the events, one event is designated as the leader. Subsequent events are followers. At the first segment boundary, each follower uses its own timecode and the leader's timecode to align the frame that it emits with the frame that the leader is emitting. The events are now all locked together.
How resynchronization works
Elemental Live continually checks the timecode for the same segment in all the locked events. If the segment in one event has a different timecode, then it is considered to be out sync.
Elemental Live resynchronizes the output of an event by inserting a short segment and a presentation timestamp (PTS) discontinuity tag.
Keep this detect-and-correct behavior in mind. Output locking doesn't guarantee that output always staty in sync. Rather, the guarantee is that when a drift occurs, Elemental Live resynchronizes.
Inability to detect and correct
As the event runs, there might be times when the event can't detect and correct. For example, if the current source doesn't include a timecode because it is slate content.
Even in this case, Elemental Live continues to attempt to synchronize. For example, if the content changes so that a timecode is present again in the source, then Elemental Live will resync again.
