Fundamentals and Evolution of MPEG-2 Systems: Paving the MPEG Road

15The Real-Time Interface for Transport Streams

Why a real-time interface is needed for the delivery of transport streams. The choice for a maximum value for the jitter in byte arrival of a transport stream and the consequences thereof for the receiver.

When it became clear that digital TV applications would use transport streams, ICs were developed for set-top boxes for digital TV services across satellite, cable and other networks, upon which the need arose for a real-time interface for system decoders. The STD model assumes an idealized decoder model and a system stream delivered with mathematical accuracy. Decoder manufacturers can compensate for ways in which their actual design differs from the processing in the STD; however, in practice the system stream is not delivered with mathematical accuracy, but with characteristics specific for the applied delivery network(s), such as jitter and variable, sometimes unknown, delays.

For decoder manufacturers and for more general interoperability reasons it is desirable that a real-time interface is designed for the delivery of system streams. In particular for transport streams the need for such interface was recognized, as the characteristics of its delivery are typically fully determined by the network. An agreed upon real-time interface, met by practical networks, ensures that ‘universal’ system decoders can be designed, suitable for each network with delivery characteristics within the constraints of this interface. At the ...