Among the family of MAC or

Multiplexed Analogue Components Multiplexed Analogue Components (MAC) was an analog television standard where luminance and chrominance components were transmitted separately. This was an evolution from older color TV systems (such as PAL or SECAM) where there was interferen ...

systems for

television broadcasting A television broadcaster or television network is a telecommunications network for the distribution of television content, where a central operation provides programming to many television stations, pay television providers or, in the United ...

, D-MAC is a reduced bandwidth variant designed for transmission down cable. * The data is duobinary coded with a data burst rate of 20.25 Mbit/s so that 0° as well as ±90° phasors are used. * D-MAC has a bandwidth of 8.4 MHz versus 27 MHz for C-MAC. * Most cable systems work on

EBU The European Broadcasting Union (EBU; , UER) is an alliance of Public broadcasting, public service media organisations in countries within the European Broadcasting Area (EBA) or who are member states of the Council of Europe, members of the ...

7 MHz channel spacing, so this approach did not work universally. * D-MAC's bandwidth problems were later fixed by D2-MAC.

D2-MAC: a fix for D-MAC

D-MAC consumed too much bandwidth for many applications, so D2-MAC was designed for European cable TV systems.

Luminance and chrominance

MAC transmits luminance and chrominance data separately in time rather than separately in frequency (as other analog television formats do, such as composite video).

Audio and scrambling (selective access)

* Audio, in a format similar to

NICAM Near Instantaneous Companded Audio Multiplex (NICAM) is an early form of lossy compression for digital audio. It was originally developed in the early 1970s for point-to-point links within broadcasting networks.Croll, M.G., Osborne, D.W. and Spi ...

was transmitted digitally rather than as an FM subcarrier. * The MAC standard included a standard scrambling system,

EuroCrypt EuroCrypt is a conditional access system for Multiplexed Analogue Components-encoded analogue satellite television Satellite television is a service that delivers television programming to viewers by relaying it from a communications satell ...

, a precursor to the standard DVB-CSA encryption system.

History and politics

MAC was developed by the UK's

Independent Broadcasting Authority The Independent Broadcasting Authority (IBA) was the regulatory body in the United Kingdom for commercial television ( ITV and Channel 4 and limited satellite television regulation – cable television was the responsibility of the Cable Author ...

(IBA) and in 1982 was adopted as the transmission format for the UK's forthcoming

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.ITU Radio Regulations, Section IV. Radio Stations and Systems ...

(DBS) television services (eventually provided by

British Satellite Broadcasting British Satellite Broadcasting plc (BSB) was a television company, based in London, that provided satellite television, direct broadcast satellite television services to the United Kingdom. It started broadcasting on 25 March 1990. The company ...

). The following year MAC was adopted by the

European Broadcasting Union The European Broadcasting Union (EBU; , UER) is an alliance of Public broadcasting, public service media organisations in countries within the European Broadcasting Area (EBA) or who are member states of the Council of Europe, members of the ...

(EBU) as the standard for all DBS. By 1986, despite there being two standards, D-MAC and D2-MAC, favoured by different countries in Europe, an EU Directive imposed MAC on the national DBS broadcasters, to provide a stepping stone from analogue

PAL Phase Alternating Line (PAL) is a color encoding system for analog television. It was one of three major analogue colour television standards, the others being NTSC and SECAM. In most countries it was broadcast at 625 lines, 50 fields (25 ...

and

Secam SECAM, also written SÉCAM (, ''Séquentiel de couleur à mémoire'', French for ''sequential colour memory''), is an analog color television system that was used in France, Russia and some other countries or territories of Europe and Africa. ...

formats to the eventual high definition and

digital Digital usually refers to something using discrete digits, often binary digits. Businesses *Digital bank, a form of financial institution *Digital Equipment Corporation (DEC) or Digital, a computer company *Digital Research (DR or DRI), a software ...

television of the future, with European TV manufacturers in a privileged position to provide the equipment required. However, the

Astra Astra (Latin for "stars") may refer to: People * Astra (name) Places * Astra, Chubut, a village in Argentina * Astra (Isauria), a town of ancient Isauria, now in Turkey * Astra, one suggested name for a hypothetical fifth planet that became t ...

satellite system was also starting up at this time (the first satellite,

Astra 1A Astra 1A was the first satellite launched and operated by SES (Société Européenne des Satellites), launched in December 1988. During its early days, it was often referred to as the Astra Satellite, as SES only operated one satellite origi ...

was launched in 1989) and that operated outside of the EU's MAC requirements, due to being a non-DBS satellite. Despite further pressure from the EU (including a further Directive originally intended to make MAC provision compulsory in TV sets, and a subsidy to broadcasters to use the MAC format), most broadcasters outside Scandinavia preferred the lower cost of PAL transmission and receiving equipment. In the 2000s, the use of D-MAC and D2-MAC ceased when the satellite broadcasts of the channels concern changed to DVB-S format.''High Above'' Broadgate Publications (April, 2010).

References

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External links