A packet insertion mechanism at the front end of a time-synchronized digital television transmission system multiplexes, along with standard packets, packets whose payload is to be transmitted with redundancy for added robustness. The multiplexer also inputs placeholder packets to accommodate duplicated content of the robust packets. Multiplexing of the robust and placeholder packets is configured to alternate and to interleave with the multiplexing of standard packets. The distribution of the robust packets within a frame is determined by the number of robust packets.