o investigate and compare a number of temporal filtering with motion compensated information of the proposed all digital (transmission) systems capable of being intro- DATV channels used to minimise subjective effects. duced alongside ('simulcasting') the existing 525 line broadcasts For contribution links, where post production editing is required, and suitable for either terrestrial or satellite or cable distribution, the source bit rate of the active lines at roughly 1Gbit/s can be using digital techniques for both source coding and channel coding. compressed to the 560Mbit/s ISDN level by the use of differential Proposed systems of bit rate production have been claimed to permit pulse code modulation (DPCM). 525 line broadcast TV at bit rates from about 5Mbit/s to 10Mbit/s and HDTV at between 30Mbit/s to 50Mbit/s. All the proposed digital systems use video bandwidth compression after basic anal- 57.2.4.2 Hi Vision ogue to digital conversion including interlace scanning, removal of source redundancy, making full use of human perception limitation- The NHK broadcasting organisation, in collaboration with Japanese S, three dimensional processing (time as third dimension) and en- industry, has developed and widely demonstrated an HDTV system tropy coding. capable of excellent quality on closed circuit. The system was Because a digital system could be transmitted at much lower originally proposed as a world studio production standard, for which transmitter power for equal coverage than conventional analogue purpose it has gained support primarily in 60Hz areas. It was not AM systems, the possibility of using existing 'taboo' (adjacent developed as a compatible system, but subsequently a number of channels etc.) terrestrial channels for additional 525/625 line chan- bandwidth reduction systems - MUSE (Multiple Sub-Nyquist- nels is also under investigation. Sampling Encoding) family - have been developed that permit the Bit rate reduction for the distribution of digital TV (broadcast, and 1125 line material to be tr