VHS
The Video Home System[1] (better known by its abbreviation VHS[2]) is a consumer-level video standard developed by Japanese company JVC and launched in 1976.
History
It was first introduced at the Consumer Electronics Show in Chicago on June 4, 1977, and later marketed to the public on October 1, 1977. During the late part of the 1970s and the early 1980s, the home video industry was involved in the VHS vs. Betamax war, which VHS would eventually win. Advantages of VHS included longer playing time, faster rewinding and fast-forwarding, and a less-complex, lower-cost tape transport mechanism. The VHS technology was owned by JVC, but they allowed other manufacturers to license the format for much smaller fees than Sony did, leading to wide adoption by non-JVC companies.[3] VHS would eventually succeed as the dominant home video format, surpassing others by the early 1980s and remaining dominant through the 90s.
In later years, optical disc formats began to offer better quality than video tape. The earliest of these formats, Laserdisc, was not widely adopted, but the subsequent DVD (Digital Versatile Disc) format eventually did achieve mass acceptance and replaced VHS as the preferred method of distribution after 2000.[4] By 2006, film studios in the United States had stopped releasing new movie titles in VHS format. On December 31, 2008, the last major United States supplier of pre-recorded VHS tapes, Distribution Video Audio Inc. of Palm Harbor, Florida, shipped its final truckload.[5] , most of the VHS tapes being produced are blank.
Capacity
A VHS cassette holds a maximum of about 430 m (1,410 ft.) of tape at the lowest acceptable tape thickness, giving a maximum playing time of about 3.5 hours for NTSC and 5 hours for PAL at "standard" (SP) quality. Other speeds include LP and EP/SLP which double and triple the recording time, for NTSC regions. These speed reductions cause a slight reduction in video quality (from 250 lines to 230 analog lines horizontal); also, tapes recorded at the lower speed often exhibit poor playback performance on recorders other than the one they were produced on. Because of this, commercial prerecorded tapes were almost always recorded in SP mode.
Video recording
VHS tapes have approximately 3 MHz of video bandwidth and 400 kHz of chroma bandwidth, which is achieved at a relatively low tape speed by the use of helical scan recording of a frequency modulated luminance (black and white) signal, with a down-converted "color under" chroma (color) signal recorded directly at the baseband. Each helical track contains a single field ('even' or 'odd' field, equivalent to half a frame) encoded as an analog raster scan, similar to analog TV broadcasts. The horizontal resolution is 170 lines per scanline, and the vertical resolution (the number of scanlines) is the same as the respective analog TV standard (575 for PAL or 486 for NTSC). In modern-day digital terminology, VHS is roughly equivalent to 333x480 pixels luma and 40x480 chroma resolutions (333x480 pixels=159,840 pixels or 0.16MP (1/6 of a MegaPixel)).[6]
JVC would counter 1985's SuperBeta with VHS HQ, or High Quality. The frequency modulation of the VHS luminance signal is limited to 3 megahertz which makes higher resolutions impossible, but an HQ branded deck includes luminance noise reduction, chroma noise reduction, white clip extension, and improved sharpness circuitry. The effect was to increase the apparent horizontal resolution of a VHS recording from 240 to 250 analog (equivalent to 333 pixels from left-to-right, in digital terminology). The major VHS OEMs resisted HQ due to cost concerns, eventually resulting in JVC reducing the requirements for the HQ brand to white clip extension plus one other improvement.
In 1987 JVC introduced the new format called Super VHS which extended the bandwidth to over 5 megahertz, yielding 420 analog horizontal (560 pixels left-to-right).