When you have a sync-group, how does the player check to see if it is in sync?
All synced devices belong to a sync group. When a player is added to a sync group, the sync group JSON object is included in the configuration file your players download from our server.
This is a way of identifying which device has been assigned the primary player in your sync group, as one of the devices in the group is always assigned as the master player. This is the device that is used to coordinate all other devices in the group. Their content start times mirror this master player.
The allocation of the master player will vary between player types and the order the players are added to the sync group, but after all players have been setup, the master player is usually the player with the lower serial number in Signagelive
Is sync co-ordinated by video playback events (end of an asset/frame by frame) or is it based on a time sync between the players?
This will be dependent on your player type.
Brightsigns and Samsung devices (no additional licence required), along with IADea players (providing you have an AnyTiles licence) can achieve frame by frame sync. This allows them to refresh their link with the master after every video frame, per video file in your playlist.
Other devices (LG WebOS) will sync based on the start of each asset in the playlist. For these devices we would recommend the use of shorter 2 - 4 minute long video files, to ensure the content and sync is kept in line and regularly up to date.
If it is time-based, what is the interval that it is checking on?
Sync with the master player is based on the content's duration or playback, and not on any external interval.