Hi-Vision

MUSE (Multiple sub-Nyquist sampling encoding), was a dot-interlaced digital video compression system that used analog modulation for transmission to deliver 1125-line high definition video signals to the home. Japan had the earliest working HDTV system, which was named Hi-Vision (a contraction of HIgh-definition teleVISION) with design efforts going back to 1979. The country began broadcasting wideband analog HDTV signals in the late 1980s using 1035 active lines interlaced in the standard 2:1 ratio (1035i) with 1125-lines total.

MUSE, a compression system for Hi-Vision signals, was developed by NHK Science & Technology Research Laboratories in the 1980s, employed 2-dimensional filtering, dot-interlacing, motion-vector compensation and line-sequential color encoding with time compression to 'fold' an original 20 MHz source Hi-Vision signal into a bandwidth of 8.1 MHz.

Modulation research

DPCM Audio compression format: DPCM quasi-instantaneous companding

MUSE is a 1125 line system (1035 visible), and is not pulse and sync compatible with the digital 1080 line system used by modern HDTV. Originally, it was a 1125 line, interlaced, 60 Hz, system with a 5/3 (1.66:1) aspect ratio and an optimal viewing distance of roughly 3.3H.

For terrestrial MUSE transmission a bandwidth limited FM system was devised. A satellite transmission system uses uncompressed FM.

The pre-compression bandwidth for Y is 20 MHz, and the pre-compression bandwidth for chrominance is a 7.425 MHz carrier.

The Japanese initially explored the idea of frequency modulation of a conventionally constructed composite signal. This would create a signal similar in structure to the Y/C NTSC signal - with the Y at the lower frequencies and the C above. Approximately 3 kW of power would be required, in order to get 40 dB of signal to noise ratio for a composite FM signal in the 22 GHz band. This was incompatible with satellite broadcast techniques and bandwidth.

To overcome this limitation, it was decided to use a separate transmission of Y and C. This reduces the effective frequency range and lowers the required power. Approximately 570 W (360 for Y and 210 for C) would be needed in order to get a 40 dB of signal to noise ratio for a separate Y/C FM signal in the 22 GHz satellite band. This was feasible.

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