Video Delivery Disc

Video Delivery Disc

12-inch VDD in 1983
Media type	video playback media
Capacity	30 min. (20-inch) 45 min. (16-inch) 60 min. (12-inch)
Read mechanism	stylus

The Video Delivery Disc is a video storage format and playback system developed by Boradcasting Corporation of Themiclesia, whereby video could be distributed and replayed on common television sets. The physical medium was similar to, and developed from, the phonograph record, but VDD discs had much denser grooves and were read by a stylus detecting electric capacitance rather than vibration. The format was originally designed for broadcasting, but in development BCT later repositioned the format for home viewing of television shows, theatre, and cinema.

The VDD was first conceived in 1955 by Mark Nya, a BCT engineer, but only authorized for development in 1963. Playable discs were demonstrated in 1968 when the discs could hold 10 minutes of monochrome video. BCT promised an 1970 release, which was achieved but not without severe compromises. The recording density was improved several times after release, but compatibility with existing players was maintained with upgrades to styli. Sales of VDD machines continued until 1990, and discs were made until 1994.

Formats

20-inch

The 20-inch disc was the first VDD format released for public consumption in 1971 but post-dates the 16-inch in development. Engineers were troubled by the short recording times achieved on the 16-inch and, faced with a deadline the company imposed, resorted to increasing the size of the disc to increase recording time. The four extra inches in the disc's diameter allowed more than a 50% improvement in recording time. 20-inch audio discs were used as early as 1905 in Casaterra and were actually issued by the BCT in 1909 but were entirely obsolete by 1972. Because the recording density of the 20-inch disc was lower than the 16-inch and 12-inch versions, it did not require a protective case during transportation; however, a felt sleeve was used to protect the large disc against impact.

The 20-inch disc could hold 10 minutes of monochrome video per side, and both sides were typically used to create a 20-minute playback. This format was suited to television shows, many of which occupied 30-minute blocks on the broadcasting schedule. Only 20 minutes was required because 10 minutes of the 30-minute block was used for advertisement. A separate audio disc was bundled with the video disc to be played on a separate record player. The two discs were manually synchronized. The 20-inch disc was phased out in 1981.

16-inch

The 16-inch disc was launched in 1973 and was capable of holding 25.5 minutes of colour video per side

See also

• Themiclesia