A marker can leave while its history remains
Counting only the discontinuity tags currently visible in a live playlist loses history as the window moves. RFC 8216 uses a discontinuity sequence to preserve the identity of timeline regions across updates and renditions. Review that state alongside media sequence numbering; they answer different questions.
Imagine a playlist beginning with discontinuity sequence 8 and containing one boundary before a retained segment. That segment belongs to region 9 in this simplified example. When the old boundary is removed with earlier media, the retained segment must not appear to move back into region 8.
Compare corresponding media
Archive a video and audio playlist snapshot from the same production interval. Find a known corresponding passage using timeline evidence, then compare its discontinuity identity. Do not assume matching media sequence numbers establish alignment between different playlists.
Inspect the update that removes the boundary as well as the update that introduces it. A failure may remain hidden while the marker is visible, then emerge only after enough old media has been trimmed. That makes a single startup snapshot a weak acceptance artifact.
Own the restart and retention state
Include discontinuity bookkeeping in the packager's restart design. A counter written only to transient memory may need an explicit recovery policy. The policy should preserve retained content's meaning, rather than merely choosing numbers that look tidy after restart.
If an inconsistency is found, retain the affected manifest pair and packager generation identifiers before making changes. A player symptom alone cannot establish whether the origin, a stale intermediary or the client supplied the inconsistent view. No production incident is claimed here.
Questions answered
Is discontinuity sequence the same as media sequence?
No. They track different relationships; one cannot replace the other in a review.
Can I reset the discontinuity counter whenever old files are deleted?
Do not reset retained media's identity merely because a marker leaves the visible window. Follow the protocol's update rules.
Sources & further reading
Official references for the subjects discussed. Service terms and device software can change.