Aggregated data is typically output in a "First Come First Serve" (FCFS) manner where the order in which the line memories are filled is the order in which they are output. The output video streams are treated as independent streams but the processor can determine how to synchronize them once received.
Although less common, some GMSL deserializers support synchronous aggregation which creates a "superframe". A superframe can either be side-by-side or line interleaved formats but requires all data sources to use the same resolution and virtual channel assignment, and they must be precisely synchronized. This results in a single stream for one superframe of data