Whether the channel is cable, satellite, or terrestrial, the problems are much the same. Metadata describing the transmission must be encoded into the transport stream in a standardized way. In broadcasting, there is much less control of the signal quality and noise or interference is a possibility. The addition of error correction obviously increases the bit rate as far as the transmitter or cable is concerned. Unfortunately, reliable, economical radio and cable-transmission of data requires more than serializing the data.
Practical systems require channel coding.
8.2 Remultiplexing Remultiplexing is a complex task because it has to output a compliant bit stream that is assembled from parts of others. The required data from a given input transport stream can be selected with reference to the program association table and the program map tables that will disclose the PIDs of the programs required. As the position of packets containing PCR may be different in the new multiplex, the remultiplexer may need to edit the PCR values to reflect their new position on the time axis. If the sum of the selected program stream bit rates is less than the output bit rate, the remultiplexer will create stuffing packets with suitable PIDs. However, if the transport streams have come from statistical multiplexers, it is possible that the instantaneous bit rate of the new transport stream will exceed the channel capacity.