VHD
Encyclopedia
Video High Density was a videodisc
format which was marketed predominantly in Japan
by JVC
. There was also an audio-only variant, Audio High Density (AHD).
—like the rival SelectaVision
system from RCA
, also known as CED, the user never handled the disc directly. The entire caddy is inserted into the player, and then withdrawn, leaving the disc inside where it will be loaded and start playing. At the end of the side the disc must be removed, turned over and re-inserted.
Like the RCA system, the signal is recorded on the discs as variations in capacitance, a conductive coating on the disc itself forming part of a resonant circuit. A diamond stylus reads the signal, though unlike CED there are no actual grooves—the stylus follows the tracks electronically, like a compact disc
. Naturally this means less wear, though there is still physical contact (unlike LaserDisc
) so some wear would still occur.
The discs contain two frames
(four fields
) per revolution, and play in CAV
mode. This makes trick play simple, as all frames start at the same place on the disc, but having two frames per rotation means that true freeze frame
was not possible—there would be some "jitter" on moving sequences (discs which were designed to be used a frame at a time—such as picture catalogues—doubled up the frames, to get true stills at the cost of reduced capacity).
VHD was always intended as a highly interactive format, and many trick-play and non-linear features were supported, directly by the players or via an optional computer interface. Applications included interactive adventure games, and car engine diagnostic tools.
in 1983. By this time, both LaserDisc
and CED
were already suffering from the onslaught of VHS
and Betamax
VCRs. Despite demonstrating the player at several Consumer Electronics Shows, JVC opted not to release VHD as a consumer product in North America.
It found its main niche as a karaoke
system, and was also used in anime
video games and interactive training systems. Commercial versions were available in the UK (and probably the US) for training, demonstration and fault diagnosis.
A stereoscopic system was also sold in Japan, using double-speed discs with alternate-eye images and LCD glasses
to pass the correct view to each eye.
VHD was essentially defunct after 1984.
following in Japan, and discs and players are both still collected.
Videodisc
Videodisc is a general term for a laser- or stylus-readable random-access circular disc that contains both audio and analog video signals recorded in an analog form...
format which was marketed predominantly in Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
by JVC
JVC
, usually referred to as JVC, is a Japanese international consumer and professional electronics corporation based in Yokohama, Japan which was founded in 1927...
. There was also an audio-only variant, Audio High Density (AHD).
Technology
VHD discs are 25 cm (9 5/6 inches) in diameter, and store up to 60 minutes of video per side. Each disc is stored in a caddyCaddy (hardware)
In computer hardware, a caddy refers to a sheath used to hold some media.If the medium is a hard disk drive, the caddy is also referred to as a disk enclosure, which is discussed there...
—like the rival SelectaVision
SelectaVision
The Capacitance Electronic Disc was an analog video video disc playback system developed by RCA, in which video and audio could be played back on a TV set using a special needle and high-density groove system similar to phonograph records....
system from RCA
RCA
RCA Corporation, founded as the Radio Corporation of America, was an American electronics company in existence from 1919 to 1986. The RCA trademark is currently owned by the French conglomerate Technicolor SA through RCA Trademark Management S.A., a company owned by Technicolor...
, also known as CED, the user never handled the disc directly. The entire caddy is inserted into the player, and then withdrawn, leaving the disc inside where it will be loaded and start playing. At the end of the side the disc must be removed, turned over and re-inserted.
Like the RCA system, the signal is recorded on the discs as variations in capacitance, a conductive coating on the disc itself forming part of a resonant circuit. A diamond stylus reads the signal, though unlike CED there are no actual grooves—the stylus follows the tracks electronically, like a compact disc
Compact Disc
The Compact Disc is an optical disc used to store digital data. It was originally developed to store and playback sound recordings exclusively, but later expanded to encompass data storage , write-once audio and data storage , rewritable media , Video Compact Discs , Super Video Compact Discs ,...
. Naturally this means less wear, though there is still physical contact (unlike LaserDisc
Laserdisc
LaserDisc was a home video format and the first commercial optical disc storage medium. Initially licensed, sold, and marketed as MCA DiscoVision in North America in 1978, the technology was previously referred to interally as Optical Videodisc System, Reflective Optical Videodisc, Laser Optical...
) so some wear would still occur.
The discs contain two frames
Data frame
In computer networking and telecommunication, a frame is a digital data transmission unit or data packet that includes frame synchronization, i.e. a sequence of bits or symbols making it possible for the receiver to detect the beginning and end of the packet in the stream of symbols or bits...
(four fields
Field (video)
In video, a field is one of the many still images which are displayed sequentially to create the impression of motion on the screen. Two fields comprise one video frame...
) per revolution, and play in CAV
Constant angular velocity
In optical storage, constant angular velocity is a qualifier for the rated speed of an optical disc drive, and may also be applied to the writing speed of recordable discs...
mode. This makes trick play simple, as all frames start at the same place on the disc, but having two frames per rotation means that true freeze frame
Freeze frame
- Film and Television :*Freeze frame shot, a cinematographic technique*Freeze frame television, a technique making use of freeze frame shots*Freeze Frame, a game on The Price is Right...
was not possible—there would be some "jitter" on moving sequences (discs which were designed to be used a frame at a time—such as picture catalogues—doubled up the frames, to get true stills at the cost of reduced capacity).
VHD was always intended as a highly interactive format, and many trick-play and non-linear features were supported, directly by the players or via an optional computer interface. Applications included interactive adventure games, and car engine diagnostic tools.
History
VHD was first demonstrated in 1978, and after numerous advertisements in 1981/1982 National Geographic magazines, it was eventually released in JapanJapan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
in 1983. By this time, both LaserDisc
Laserdisc
LaserDisc was a home video format and the first commercial optical disc storage medium. Initially licensed, sold, and marketed as MCA DiscoVision in North America in 1978, the technology was previously referred to interally as Optical Videodisc System, Reflective Optical Videodisc, Laser Optical...
and CED
SelectaVision
The Capacitance Electronic Disc was an analog video video disc playback system developed by RCA, in which video and audio could be played back on a TV set using a special needle and high-density groove system similar to phonograph records....
were already suffering from the onslaught of VHS
VHS
The Video Home System is a consumer-level analog recording videocassette standard developed by Victor Company of Japan ....
and Betamax
Betamax
Betamax was a consumer-level analog videocassette magnetic tape recording format developed by Sony, released on May 10, 1975. The cassettes contain -wide videotape in a design similar to the earlier, professional wide, U-matic format...
VCRs. Despite demonstrating the player at several Consumer Electronics Shows, JVC opted not to release VHD as a consumer product in North America.
It found its main niche as a karaoke
Karaoke
is a form of interactive entertainment or video game in which amateur singers sing along with recorded music using a microphone and public address system. The music is typically a well-known pop song minus the lead vocal. Lyrics are usually displayed on a video screen, along with a moving symbol,...
system, and was also used in anime
Anime
is the Japanese abbreviated pronunciation of "animation". The definition sometimes changes depending on the context. In English-speaking countries, the term most commonly refers to Japanese animated cartoons....
video games and interactive training systems. Commercial versions were available in the UK (and probably the US) for training, demonstration and fault diagnosis.
A stereoscopic system was also sold in Japan, using double-speed discs with alternate-eye images and LCD glasses
LCD shutter glasses
Liquid crystal shutter glasses are glasses used in conjunction with a display screen to create the illusion of a three dimensional image, an example of stereoscopy. Each eye's glass contains a liquid crystal layer which has the property of becoming dark when voltage is applied, being otherwise...
to pass the correct view to each eye.
VHD was essentially defunct after 1984.
VHD today
VHD was not a great success as a consumer product, but the system sold well for the applications discussed above. VHD has something of a cultCult
The word cult in current popular usage usually refers to a group whose beliefs or practices are considered abnormal or bizarre. The word originally denoted a system of ritual practices...
following in Japan, and discs and players are both still collected.