Hardware theme

VHD videodiscs are 25cm grooveless vinyl discs. Non-linear playback is easy, so they are suitable for games. They play back video much like a DVD.


The first video game about VHD was released in 1985.

Like a Laserdisc, SelectaVision CED, or Magnavision(DiscoVision). VHD was like a cross between an ancient vinyl records and a modern DVDs. The discs were manufactured cheaper than Laserdiscs and more durable than CEDs. In fact, while Laserdiscs needed special presses and CEDs needed to be entirely manufactured in a cleanroom, VHDs could be made on a stander vinyl record press as if it were an old fashioned audio record. Note that this also meant *anyone* could make a VHD, no need to hire RCA to make a CED for them (no one else had the resources) or buying the equipment and a license for the right to make Laserdics. There were no groves on the VDH discs, instead there were pits like an optical dist. But instead of a laser, a diamond tipped needle was precisely 'hovered' over it to read the pits using electronics to guide its position (as if it were a laser). The needle did require physical contact with the disc, so it would wear out the disk eventually. But they lasted many times longer than audio records and CEDs. The discs used a CAV scheme with a set number of frames/time measurement per revolution. It could pause, seek, frame, and jump like a CAV laserdisc or DVD video. There were four 'tracks' on the disk, two were needed to record video, 1 track could record sound or still pictures; these could be mixed and matched however needed. Two standards were planned a video and 2 audio channels disc and a 3 audio channels + still pictures dics. The audio+pics disc was canceled when Audio CD became successful. But many Anime discs were made, and some videogames. Since the videodiscs could do non-linear video, these videos could be played when needed for videogames. An MSX adapter was added to several VHD players that allowed the MSX to control video playback. Thus, the equivalent of a home Laserdisc system. Some MSX machines also included the ability to overlay real-time computer images on the prerecorded video image, so games like Thayer's Quest are possible.



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