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CED in the History of Media Technology


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JVC VHD AHD Disc System

1979: JVC VHD/AHD Video/Audio Disc System Prototype

Matsushita subsidiary JVC (Japan Victor Company) demonstrated their VHD/AHD disc system in 1979. This system was capacitance-based like CED, but the discs were grooveless with the stylus being guided by servo signals in the disc surface. The VHD discs initially were handled by the operator and played on a machine that looked like an audio LP turntable, but JVC used caddy housed discs when the system was marketed.

In the early 1970's a manager at RCA Records made the mistake of establishing a development contract with JVC's parent company, Matsushita, that included providing them with a prototype CED system. So JVC had full access to RCA's development of the CED system up to that time without having done any of the basic research. JVC made some changes from RCA's CED implementation to be more versatile internationally. The discs had two video frames per revolution (rather than four), and the discs spun at 900 RPM (rather than 450 RPM) for NTSC playback. By merely reducing this speed to 750 RPM the system became capable of PAL playback, so the same discs could be used in the US/Japan or the Great Britain/Europe markets.

VHD (Video High Density) was the video component of the JVC system, while the company hoped AHD (Audio High Density) would be adopted as the standard for digital or pulse code modulation (PCM) audio discs then being debated by a 29-company council. The box on the right in the photo is a demodulator that would allow the player to decode PCM-encoded discs, while the box on the left is a serial interface unit for computer control. But the VHD system faced many delays and wasn't marketed until April 1983. By that time the Philips/Sony compact disc was on the market, and the AHD format never materialized.


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