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DigiCipher 2, or simplyDCII, is a proprietary standard format of digital signal transmission and it doubles as anencryption standard with MPEG-2/MPEG-4 signalvideo compression used on manycommunications satellitetelevision and audio signals. The DCII standard was originally developed in 1997 byGeneral Instrument, which then became the Home and Network Mobility division ofMotorola, then bought byGoogle in Aug 2011, and lastly became the Home portion of the division toArris.[1]
The original attempt for a North American digital signal encryption and compression standard was DigiCipher 1, which was used most notably in the now-defunctPrimeStar medium-powerdirect broadcast satellite (DBS) system during the early 1990s. The DCII standard predates wide acceptance ofDVB-based digital terrestrial television compression (although not cable or satellite DVB) and therefore is incompatible with the DVB standard.
Approximately 70% of first-generationdigital cable networks in North America use the4DTV/DigiCipher 2 format.[2] The use of DCII is most prevalent in North American digitalcable televisionset-top boxes. DCII is also used on Motorola's 4DTV digitalsatellite televisiontuner andShaw Direct's DBS receiver.
The DigiCipher 2 encryption standard was reverse engineered in 2016.[3]
DigiCipher II uses QPSK and BPSK at the same time. The primary difference between DigiCipher 2 and DVB lies in how each standard handles SImetadata, or System Information, where DVB reserves packet identifiers from 16 to 31 for metadata, DigiCipher reserves only packet identifier 8187 for itsmaster guide table which acts as alook-up table for all other metadata tables. DigiCipher 2 also extends the MPEGprogram number that is assigned for each service in a transport stream with the concept of avirtual channel number, whereas the DVB system never defined this type of remapping preferring to use a registry ofnetwork identifiers to further differentiateprogram numbers from those used in other transport streams. There are also private non-standard additions to DVB that add virtual channel remapping usinglogical channel numbers. Also unlike DVB, all text used in descriptors can be compressed using standardHuffman coding which saves on broadcast bandwidth and loading times. DigiCipher II usesDolby Digital AC-3 audio for all channels, although MPEG-1 Level 2 audio is not supported.[2]