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Partial Ad Break Insertion

The Partial Ad Break Insertion (PABI) feature mimics a TV like experience in which if the user joins a live stream inside a mid-roll break, the user is shown mid-roll ads instead of a pre-roll ad or slate.
When the ad server returns pre-roll ads for a live stream, the manifest server will inject the pre-roll ad break before the live-point and insert the EXT-X-START tag with its TIMEOFFSET value pointing to the start of the pre-roll ad break. This default behavior ensures the entire pre-roll ad break is played before the content at the live-point. If a user joins a stream when the live-point is near a mid-roll ad break, the user will be shown the pre-roll ad break before the mid-roll ad break at the live-point.
The PABI feature instructs the manifest server ignore the pre-roll ad break and set the EXT-X-START:TIMEOFFSET value to the beginning of the mid-roll ad present at live-point. This ensures the user sees the entire mid-roll ad currently playing at the live-point without having to view the pre-roll ad break.
This functionality is only available for live streams. The manifest server inserts the pre-roll ad break atop the VOD playlist by default.
To enable PABI, you will need to specify the query_params in the bootstrap URL.
The EXT-X-START is a standard HLS tag that indicates a preferred starting point within the playlist.


  • Use client-side tracking because the client has more control over the firing of tracking beacons.
  • Partial ad breaks should only be used with server-side tracking mode if the player supports EXT-X-START.