DigiCipher 2, or simply DCII, is a proprietary standard format of digital signal transmission and it doubles as an

encryption In cryptography, encryption is the process of encoding information. This process converts the original representation of the information, known as plaintext, into an alternative form known as ciphertext. Ideally, only authorized parties can decip ...

standard with MPEG-2/MPEG-4 signal

video compression In information theory, data compression, source coding, or bit-rate reduction is the process of encoding information using fewer bits than the original representation. Any particular compression is either lossy or lossless. Lossless compression ...

used on many

communications satellite A communications satellite is an artificial satellite that relays and amplifies radio telecommunication signals via a transponder; it creates a communication channel between a source transmitter and a receiver at different locations on Earth. C ...

television Television, sometimes shortened to TV, is a telecommunication medium for transmitting moving images and sound. The term can refer to a television set, or the medium of television transmission. Television is a mass medium for advertisin ...

and audio signals. The DCII standard was originally developed in 1997 by

General Instrument General Instrument (GI) was an American electronics manufacturer based in Horsham, Pennsylvania, specializing in semiconductors and cable television equipment. They formed in New York City in 1923 as an electronics manufacturer. During the 1950s, ...

, which then became the Home and Network Mobility division of

Motorola Motorola, Inc. () was an American Multinational corporation, multinational telecommunications company based in Schaumburg, Illinois, United States. After having lost $4.3 billion from 2007 to 2009, the company split into two independent p ...

, then bought by

Google Google LLC () is an American multinational technology company focusing on search engine technology, online advertising, cloud computing, computer software, quantum computing, e-commerce, artificial intelligence, and consumer electronics. ...

in Aug 2011, and lastly became the Home portion of the division to

Arris In architecture, an arris is the sharp edge formed by the intersection of two surfaces, such as the corner of a masonry unit; the edge of a timber in timber framing; the junction between two planes of plaster or any intersection of divergent a ...

. 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 PrimeStar was a U.S. direct broadcast satellite broadcasting company formed in 1991 by a consortium of cable television system operators ( TCI Satellite Entertainment Group, Time Warner Cable, Cox Communications, Comcast and MediaOne) and GE Ame ...

medium-power

direct broadcast satellite Satellite television is a service that delivers television programming to viewers by relaying it from a communications satellite orbiting the Earth directly to the viewer's location. The signals are received via an outdoor parabolic antenna comm ...

(DBS) system during the early 1990s. The DCII standard predates wide acceptance of

DVB Digital Video Broadcasting (DVB) is a set of international open standards for digital television. DVB standards are maintained by the DVB Project, an international industry consortium, and are published by a Joint Technical Committee (JTC) o ...

-based digital terrestrial television compression (although not cable or satellite DVB) and therefore is incompatible with the DVB standard. Approximately 70% of newer first-generation

digital cable Digital cable is the distribution of cable television using digital data and video compression. The technology was first developed by General Instrument. By 2000, most cable companies offered digital features, eventually replacing their previou ...

networks in North America use the 4DTV/DigiCipher 2 format. The use of DCII is most prevalent in North American digital

cable television Cable television is a system of delivering television programming to consumers via radio frequency (RF) signals transmitted through coaxial cables, or in more recent systems, light pulses through fibre-optic cables. This contrasts with broa ...

set-top box A set-top box (STB), also colloquially known as a cable box and historically television decoder, is an information appliance device that generally contains a TV-tuner input and displays output to a television set and an external source of sign ...

es. DCII is also used on Motorola's 4DTV digital

satellite television Satellite television is a service that delivers television programming to viewers by relaying it from a communications satellite orbiting the Earth directly to the viewer's location. The signals are received via an outdoor parabolic antenna comm ...

tuner and

Shaw Direct Shaw Direct is a direct broadcast satellite television distributor in Canada and a subsidiary of the telecommunications company Shaw Communications. As of 2010, Shaw Direct had over 900,000 subscribers. It broadcasts on Ku band from two communic ...

's DBS receiver. The DigiCipher 2 encryption standard was reverse engineered in 2016.

Technical specifications

DigiCipher II uses QPSK and BPSK at the same time. The primary difference between DigiCipher 2 and DVB lies in how each standard handles SI

metadata Metadata is "data that provides information about other data", but not the content of the data, such as the text of a message or the image itself. There are many distinct types of metadata, including: * Descriptive metadata – the descriptive ...

, 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 In most telecommunications organizations, a virtual channel is a method of remapping the ''program number'' as used in H.222 Program Association Tables and Program Mapping Tables to a channel number that can be entered via digits on a receiver's ...

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 In computer science and information theory, a Huffman code is a particular type of optimal prefix code that is commonly used for lossless data compression. The process of finding or using such a code proceeds by means of Huffman coding, an algori ...

which saves on broadcast bandwidth and loading times. DigiCipher II uses Dolby Digital AC-3 audio for all channels, although MPEG-1 Level 2 audio is not supported.

External links

Technical page on digital satellite signalsHistorical Perspective: HBO Implements Scrambling

References

{{broadcast encryption Cryptographic protocols Digital television Television terminology Conditional-access television broadcasting Digital rights management systems 1997 introductions Telecommunications-related introductions in 1997 Audiovisual introductions in 1997