|
Video Cassette Recording (VCR) is an early domestic analog recording format designed by Philips. It was the first successful consumer-level home videocassette recorder (VCR) system. Later variants included the VCR-LP and Super Video (SVR) formats. The VCR format was introduced in 1972, just after the Sony U-matic format in 1971. Although at first glance the two might appear to have been competing formats, they were aimed at very different markets. U-matic was introduced as a professional television production format, whilst VCR was targeted particularly at educational but also domestic users. Unlike some other early formats such as Cartrivision, the VCR format does record a high-quality video signal without resorting to Skip field. Home video systems had previously been available, but they were open-reel systems (most notably made by Sony) and were expensive to both buy and operate. They were also unreliable and often only recorded in black and white such as the EIAJ-1. The VCR system was easy to use and recorded in colour but was still expensive: when it was introduced in 1972 the N1500 recorder cost nearly UK £600 (). By comparison a small car (the Morris Mini) could be purchased for just over £600. The VCR format used large square cassettes with 2 co-axial reels, one on top of the other, containing half inch (12.7 mm) wide chrome dioxide magnetic tape. Three playing times were available: 30, 45 and 60 minutes. The 60-minute videocassettes proved very unreliable, suffering numerous snags and breakages due to the very thin 17μm video tape. Tapes of 45 minutes or less contained 20 μm thickness tape. The mechanically complicated recorders themselves also proved somewhat unreliable. One particularly common failing occurred should tape slack develop within the cassette; the tape from the top (takeup) spool may droop into the path of the bottom (supply) spool and become entangled in it if rewind was selected. The cassette would then completely jam and require dismantling to clear the problem, and the tape would then be creased and damaged. The system predated the development of the slant azimuth technique to prevent crosstalk between adjacent video tracks, so it had to use an unrecorded guard band between tracks. This required the system to run at a high tape speed of 11.26〔N1500 Service Manual published by Philips〕 inches per second. The Philips VCR system was groundbreaking and brought together many advances in video recording technology to produce the first truly practical home video cassette system. The very first Philips N1500 model included all the essential elements of a domestic video cassette recorder: * Simple loading of cassette and simple operation by "Piano Key" controls, with full auto-stop at tape ends. * A tuner for recording off-air television programmes. * A clock with timer for unattended recordings. * A modulator to allow connection to a normal (for the time) television receiver without audio and video input connectors. The Philips VCR system was only marketed in the U.K. and mainland Europe. In mid-1977, Philips announced they were considering distribution of the format in North America, and it was test marketed for several months. Because the format was initially designed only for use with the 625-line 50 Hz PAL system, VCR units had to be modified in order to work with the 60 Hz NTSC system. Unfortunately, for mechanical and electronic reasons, the tape speed had to be increased by 20%, which resulted in a 60-minute PAL tape running for 50 minutes in a NTSC machine. DuPont announced a thinner videotape formulation that would allow a 60-minute NTSC VCR tape (and roughly 70 minutes in PAL), but the tape was even less reliable than previous formulations. Ultimately, Philips abandoned any hope of trying to sell their VCR format in North America, partly because of the reliability issues, and partly because of the introduction of VHS that same year. ==Variants== VCR later evolved into a related format known as VCR-LP. This exploited slant azimuth to greatly increase the recording time. Although both formats used identical VCR cassettes, the recordings were incompatible between the two systems, and few if any dual-format recorders existed. Philips N1700, released in 1977, supported the VCR-LP format. A later even longer-playing variant, Super Video (SVR) was manufactured by Grundig exclusively. SVR was designed to exclusively use BASF and Agfa -manufactured chrome-dioxide tape in cassettes that were identical to the earlier Philips ones, with the exception of a small actuator added to the bottom of the cassette. This meant that only the BASF/Agfa tapes would work in SVR machines, but that such tapes could also be used in the older VCR and VCR-LP machines. Just as VCR-LP recordings are incompatible with VCR, so SVR recordings are incompatible with both VCR and VCR-LP. The only model to be built was the Grundig SVR4004, with a few detail variations such as optional audio/video connectors, plus a rebadged ITT 240. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Video Cassette Recording」の詳細全文を読む スポンサード リンク
|