ABT developmental history:
The ABT message command is part of the SMART protocol and was introduced in SMART 2.x. Originally intended to speed up the buffer fill of a player while attaching to a native IP Multicast, its function became more important to the backbone as we moved to adaptive bit rate last mile.
Because adaptive bit rate is built into media players, there is no opportunity to embed a SMARTcast ABT message in the player. The players are given a URL and they decide on bit rates after that. In order to have a quick play time with adaptive bit rate, the lower bit rate is played 1st, making the player buffer fill quickly.
In SMARTcast 7, the SMARTcast Master manipulates the adaptive bit rate play list in order to satisfy the first few frames from the Master itself. While these frames are playing the Master dispatches message to a Geo-located SMARTcast Endnode server and the server in turn dispatches a SMARTcast ABT Message and joins a multi-point Internet communications group. The ABT data makes a hyper-speed launch of the adaptive bit rate SMARTcast Endnode. The Endnode signals the SMARTcast Master when it is ready to serve the next frames to the End User. The SMARTcast Master manipulates the playlist to direct further play to the SMARTcast Endnode.