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DigiCipher 2, or simply DCII, is a proprietary standard format of digital signal transmission and encryption with MPEG-2/MPEG-4 signal video compression used on many communications satellite television and audio signals. The DCII standard was originally developed in 1997 by General Instrument, which is now the Home and Network Mobility division of Motorola. Google purchased this division in Aug 2011 but has since sold the Home portion of the division to Arris.〔http://www.engadget.com/2013/04/17/arris-closes-deal-to-buy-motorola-home-cable-and-internet-biz-fr/〕 The original attempt for a North American digital signal encryption and compression standard was DigiCipher 1, which was used most notably in the now-defunct PrimeStar medium-power direct broadcast satellite (DBS) system during the early 1990s. The DCII standard predates wide acceptance of DVB-based digital terrestrial television compression (although not cable or satellite DVB) and therefore is incompatible with the DVB standard. The primary difference between DigiCipher 2 and DVB lies in how each standard handles SI metadata, or System Information, where DVB reserves packet identifiers from 16 to 31 for metadata, DigiCipher reserves only packet identifier 8187 for its master guide table which acts as a ''look-up table'' for all other metadata tables. DigiCipher 2 also extends the MPEG ''program number'' that is assigned for each service in a transport stream with the concept of a virtual channel number, whereas the DVB system never defined this type of remapping preferring to use a registry of ''network'' identifiers to further differentiate ''program numbers'' from those used in other transport streams. There are also private non-standard additions to DVB that add virtual channel remapping using ''logical channel numbers''. Also unlike DVB, all text used in descriptors can be compressed using standard Huffman coding which saves on broadcast bandwidth and loading times. Approximately 70% of newer first-generation digital cable networks in North America use the 4DTV/DigiCipher 2 format. The use of DCII is most prevalent in North American digital cable television set top boxes. DCII is also used on Motorola's 4DTV digital satellite television tuner and Shaw Direct's DBS receiver. ==External links== *(Technical page on digital satellite signals ) *(Historical Perspective: HBO Implements Scrambling ) 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「DigiCipher 2」の詳細全文を読む スポンサード リンク
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