|
Digital cable is any type of cable television distribution using digital video compression for distribution. The technology was originally developed by General Instrument before being acquired by Motorola〔(【引用サイトリンク】url=http://broadband.motorola.com/business/heritage.html )〕 and subsequently acquired by ARRIS Group. Cable companies converted to digital systems during the 2000s, around the time that television signals were converted to the digital HDTV format, which was not compatible with earlier analog cable systems. In addition to providing higher resolution HD video, digital cable systems provide expanded services such as pay-per-view programming, cable internet access and cable telephone services. Most digital cable signals are encrypted, which reduced the high incidence of cable theft which occurred in analog systems. ==History== In 1990, General Instrument (now owned by ARRIS Group) demonstrated that it was possible to use digital compression to deliver high quality HDTV in a standard 6-MHz television channel. Using the same technology General Instrument (GI) demonstrated the digital transmission of multiple high quality standard definition programs in a 6 MHz cable channel. In the 1990s cable providers began to invest heavily in this new multi-channel digital TV technology to expand the number of channels and services available to subscribers. Increased competition and programming choices from Direct-broadcast satellite services such as DirecTV, Dish Network, and PrimeStar caused cable providers to seek new ways to provide more programming. Customers were increasingly interested in more channels, pay-per-view programming, digital music services, and high speed internet services. By 2000, most cable providers in the US were offering some form of digital cable TV to their customers. Digital cable technology has allowed cable providers to compress video channels so that they take up less frequency space and to offer various two-way communication capabilities. This has enabled digital cable providers to offer more channels, video on demand services (without use of a telephone line), telephone services, high speed internet services, and interactive television services. In addition, digital cable technology allows for error correction to ensure the quality of the received signal and uses a secure digital distribution system (i.e. a secure encrypted signal to prevent eavesdropping and theft of service.) Most digital cable providers use QAM for video services and DOCSIS standards for data services. Some providers have also begun to roll out video services using IPTV or Switched video. 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「digital cable」の詳細全文を読む スポンサード リンク
|