Picture quality and multiplex management in digital video broadcasting systems

Multichannel digital video broadcasting is now a practical reality. The new services made possible by this technology offer viewers much wider programme choice than current analogue systems. The wide flexibility offered to programme service providers includes the ability to trade the number of active programmes with the bit rates, and hence picture quality, within the capacity bounds of the system. The nature of the compression process is statistical and, when bit rates are minimised to maximise number of channels, occasionally quality compromises may be necessary if the bit rate cannot momentarily sustain quality. It is possible, by dynamic statistically driven allocation of available capacity, to avoid such momentary quality losses and thus improve the efficiency of the transmission system. This paper explores the relationship between picture quality and multiplex management, especially how the statistical nature of the compressed video can be matched to the MPEG packets and their allocation to services during multiplex processing.