An apparatus for generating a data stream having a series of segments using data organized in subsequent data frames, a data frame having more important and less important data. It comprises a packetiser for packetising data from a data frame into the series of segments having a first segment and a second segment, where the packetiser is operative to packetise the data of the frame so that a starting point of the more important data coincides with a starting point of the first segment and an information block adder for adding a first information block to the first segment.