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Each of the program streams (ABC1, ABC2, SBS ONE, SBS2 etc.) is individually encoded – in the future scenario, HEVC encoding provides a number of option choices:
a greatly reduced bit stream for a given quality; or
a significantly improved subjective quality for a given bandwidth; or
a combination of the two.
The combined efficiency improvements of HEVC together with the DVB-T2 transmission standard facilitates the combination of all the program streams together in a single multiplex in high quality.
Early generation encoding and multiplexing technologies required both of these process elements to be co-located as a single headend; e.g. SBS Artarmon. With today’s IP-based technology, the system architecture can be rearranged to provide significantly increased flexibility and options. For example, the encoding of each broadcaster’s services can be at its respective playout location (or elsewhere) and the multiplex function can be independently located. The statistical multiplexing can be remotely applied to each of the encoders in turn provided each of the elements are inter-connected by means of high-grade (i.e. high-bandwidth, low-latency, low-jitter) IP circuits. A further advantage of remote statistical multiplexing is that the bandwidth between playout sites and multiplex sites is of the order of a few Mbps per service rather than 270Mbps for uncompressed standard definition material; it also removes the requirement for the contribution feeds to be compressed and therefore improves the picture quality by eliminating concatenation effects.
Figure 2: Current and Future high-level multiplex architecture and infrastructure configurations
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