SEI method
Some SRT encoders like new JVC-cams , Haivision-encoder and software encoder LarixBroadcaster (iPhone/Android) can do this:
- synchronize internal clock by time-server (usually by NTP protocol).
It means all encoders have one clock:if one camera has time 11:59:59 then other cameras have same time.
- send this time inside encoded feed (SEI metainfo)
More info see here