Shareplay with live streams: HLS manifest requirements?

Question

Created Jul ’22

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We're working on enabling Shareplay for our video streaming product, but there's some confusion on what Shareplay/Group Activities actually uses to sync viewing experiences across the group, especially for a live stream.

If group members are viewing different HLS variants, the file names of the segments won't be the same (they will probably be very similar, but that isn't guaranteed). So the most likely thing in the HLS manifest for synchronizing is the EXT-X-PROGRAM-DATE-TIME.

The problem is that we do session personalization with ads, which makes the EXT-X-PROGRAM-DATE-TIME also get personalized. In order for Group Activities to keep members in sync, do the EXT-X-PROGRAM-DATE-TIME values need to always be consistent for content segments ("content" meaning not-ad-breaks)? If not, can anyone help us understand how it keeps members in sync?

Answer 1

Media Engineer OP

Apple

Jul ’22

Here is my understanding of how it works.

For live (linear) content, the timeline derived from the EXT-X-PROGRAM-DATE-TIME tag is used for synchronization. That timeline MUST be in agreement for all participants.

For VOD content, the timeline based on the start of the playlist is used for synchronization. That timeline MUST be in agreement for all participants.

Interstitials delivered to participants in a SharePlay session SHOULD match in duration. If they do not, participants receiving longer duration interstitials will miss some of the primary content. This behavior can only be overridden when all participants are using apps that support control of coordinated media playback.

Any DATE-TIME tags within an interstitial are ignored.

Note that during SharePlay, only primary content playback is synchronized and not the interstitials. So even if two participants have the same ads in an interstitial, the ads won't necessarily play in sync.