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Multiplexed Analogue Components (MAC) was an
analog television Analog television is the original television technology that uses analog signals to transmit video and audio. In an analog television broadcast, the brightness, colors and sound are represented by amplitude, phase and frequency of an analog ...
standard where
luminance Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light that passes through, is emitted from, or is reflected from a particular area, and falls with ...
and
chrominance Chrominance (''chroma'' or ''C'' for short) is the signal used in video systems to convey the color information of the picture (see YUV color model), separately from the accompanying luma signal (or Y' for short). Chrominance is usually represen ...
components were transmitted separately. This was an evolution from older color TV systems (such as
PAL Phase Alternating Line (PAL) is a colour encoding system for analogue 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 ...
or
SECAM SECAM, also written SÉCAM (, ''Séquentiel de couleur à mémoire'', French for ''color sequential with memory''), is an analog color television system that was used in France, some parts of Europe and Africa, and Russia. It was one of th ...
) where there was interference between chrominance and luminance. Originally proposed in the 1980s for use on a Europe-wide terrestrial
HDTV High-definition television (HD or HDTV) describes a television system which provides a substantially higher image resolution than the previous generation of technologies. The term has been used since 1936; in more recent times, it refers to the g ...
system, although it was never used terrestrially. However, tests have been done in France with terrestrial transmission but no commercial exploitation. Various systems were developed, collectively known as the "MAC/packet" family. In 1985 these were recommended for
satellite A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioiso ...
and cable broadcasts by the European Broadcasting Union (EBU). C-MAC/packet was intended for Direct Broadcast Satellite (DBS), D-MAC/packet was intended for wide-band cable, and D2-MAC/packet was intended both for DBS and narrow-band cable.


History

MAC was originally developed by the
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) (dates unknown) in the UK for delivering high quality pictures via direct broadcast satellites that would be independent of European countries' choice of terrestrial colour-coding standard. In 1982 it was adopted as the transmission format for the UK's forthcoming direct broadcast satellite (DBS) television services (eventually provided by
British Satellite Broadcasting British Satellite Broadcasting (BSB) was a television company, headquartered in London, that provided direct broadcast satellite television services to the United Kingdom. They started broadcasting on 25 March 1990. The company was merged with ...
). The following year MAC was adopted by 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 The European Union (EU) is a supranational political and economic union of member states that are located primarily in Europe. The union has a total area of and an estimated total population of about 447million. The EU has often been ...
imposed MAC on the national DBS broadcasters, to provide a stepping stone from analogue PAL and SECAM formats to the eventual high definition and
digital television Digital television (DTV) is the transmission of television signals using digital encoding, in contrast to the earlier analog television technology which used analog signals. At the time of its development it was considered an innovative adva ...
of the future, with european TV manufacturers in a privileged position to provide the equipment required. However, the Astra 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 origina ...
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 satellite broadcasts changed to
DVB-S Digital Video Broadcasting – Satellite (DVB-S) is the original DVB standard for Satellite Television and dates from 1995, in its first release, while development lasted from 1993 to 1997. The first commercial applications was by Star TV in Asia ...
format.


Variants

A number of broadcasting variants exist, according to the way the digital signals are multiplexed with the MAC vision signal. *
A-MAC In television electronics, A-MAC carries digital information: sound, and data-teletext on an FM subcarrier at 7 MHz. Since the vision bandwidth of a standard MAC signal is 8.4 MHz, the horizontal resolution on A-MAC has to be reduced t ...
designed as a test-bed for the MAC concept. A-MAC was never deployed by any broadcaster. S-MAC is design descendant A-MAC. * B-MAC used in South Africa by
Multichoice MultiChoice is a South African company that operates DStv, a major satellite television service in Sub-Saharan Africa and GOtv, a minor service operating in over 9 countries of this area and Showmax service. MultiChoice was formed out of the s ...
, Australia by Optus. Used in the US by
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 A ...
and
American Forces Radio and Television Service The American Forces Network (AFN) is a government television and radio broadcast service the U.S. military provides to those stationed or assigned overseas. Headquartered at Fort George G. Meade, Maryland, AFN's broadcast operations, which i ...
. Used in parts of Asia until 2005 when it was replaced by digital compression. * C-MAC required a bandwidth of about 22 MHz, making it problematic for broadcasting. It could carry eight high quality (15 kHz bandwidth) sound channels. It has a
wide-screen Widescreen images are displayed within a set of aspect ratios (relationship of image width to height) used in film, television and computer screens. In film, a widescreen film is any film image with a width-to-height aspect ratio greater than t ...
backwardly compatible variant called
E-MAC C-MAC is the television technology variant approved by the European Broadcasting Union (EBU) for satellite transmissions. The digital information is modulated using 2-4PSK (phase-shift keying), a variation of quadrature PSK where only two of the ...
. *
D-MAC Among the family of MAC or Multiplexed Analogue Components systems for television broadcasting, D-MAC is a reduced bandwidth variant designed for transmission down cable. * The data is duobinary coded with a data burst rate of 20.25Mbit/s so th ...
was a UK standard (used by
British Satellite Broadcasting British Satellite Broadcasting (BSB) was a television company, headquartered in London, that provided direct broadcast satellite television services to the United Kingdom. They started broadcasting on 25 March 1990. The company was merged with ...
) for satellite broadcasts, needing a bandwidth of approximately 10.5 MHz. It could carry eight high quality (15 kHz bandwidth) sound channels Used in Norway by
NRK NRK, an abbreviation of the Norwegian ''Norsk Rikskringkasting AS'', generally expressed in English as the Norwegian Broadcasting Corporation, is the Norwegian government-owned radio and television public broadcasting company, and the largest ...
, transmitting 3 radio channels and 1 TV channel at one D-MAC channel. *
D2-MAC D2-MAC is a satellite television transmission standard, a member of Multiplexed Analogue Components family. It was created to solve D-MAC's bandwidth problem on European cable systems. * D2-MAC uses half the data rate of D-MAC * D2-MAC has a re ...
further reduces the bandwidth to 7.8 MHz allowing usage on cable and satellite broadcast. It could carry four high quality (15 kHz bandwidth) sound channels or eight lower quality audio channels. Adopted by Germany and France, it was used on satellite broadcasts ( TV-Sat 2,
TDF 1 TDF 1 or TDF-1 was a French communications satellite which was to have been operated by Télévision de France (France Télécom). It was intended to be used to provide television broadcast services to Europe, however it failed before entering ...
and
TDF 2 TDF 2 or TDF-2 was a French communications satellite which was to have been operated by Télévision de France (France Télécom). It was intended to be used to provide television broadcast services to Europe, however it failed before entering ...
). The system was used until July 2006 in Scandinavia and until the mid-1990s for German and French sound channels. Some cable systems may still be using
D2-MAC D2-MAC is a satellite television transmission standard, a member of Multiplexed Analogue Components family. It was created to solve D-MAC's bandwidth problem on European cable systems. * D2-MAC uses half the data rate of D-MAC * D2-MAC has a re ...
in Europe and Asia. *
HD-MAC HD-MAC (High Definition Multiplexed Analogue Components) was a broadcast television standard proposed by the European Commission in 1986, as part of Eureka 95 project. It belongs to the MAC - Multiplexed Analogue Components standard family. It is ...
, an early high-definition television standard allowing for 2048x1152 resolution.


Studio (non-broadcast) MAC variants

S-MAC (''Studio MAC''): Used mostly in North America. * Processing
NTSC The first American standard for analog television broadcast was developed by National Television System Committee (NTSC)National Television System Committee (1951–1953), Report and Reports of Panel No. 11, 11-A, 12–19, with Some supplement ...
component signals yields better results (a higher quality image) than manipulating NTSC directly – thus the need to create S-MAC. * It is not possible to mix standard MAC signals in the studio environment because the (R-Y) and (B-Y) components are carried on alternate lines. * S-MAC's
SECAM SECAM, also written SÉCAM (, ''Séquentiel de couleur à mémoire'', French for ''color sequential with memory''), is an analog color television system that was used in France, some parts of Europe and Africa, and Russia. It was one of th ...
like approach to bandwidth reduction is technical annoyance, but most studio users are not affected by it. * In S-MAC the luminance is compressed by 2:1 and the two chrominance signals by 4:1 so that all three may occupy the same line. * S-MAC's vision bandwidth is 11 MHz, only ~2.8x that of
NTSC The first American standard for analog television broadcast was developed by National Television System Committee (NTSC)National Television System Committee (1951–1953), Report and Reports of Panel No. 11, 11-A, 12–19, with Some supplement ...
's vision bandwidth of 4.2 MHz. * S-MAC can be carried on a single circuit and converted losslessly to and from C-MAC at any stage. * S-MAC is well suited for SNG applications (AKA: news gathering trucks).


Technical overview

MAC transmits
luminance Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light that passes through, is emitted from, or is reflected from a particular area, and falls with ...
and
chrominance Chrominance (''chroma'' or ''C'' for short) is the signal used in video systems to convey the color information of the picture (see YUV color model), separately from the accompanying luma signal (or Y' for short). Chrominance is usually represen ...
data separately in time rather than separately in frequency (as other
analog television Analog television is the original television technology that uses analog signals to transmit video and audio. In an analog television broadcast, the brightness, colors and sound are represented by amplitude, phase and frequency of an analog ...
formats do, such as
composite video Composite video is an analog video signal format that carries standard-definition video (typically at 525 lines or 625 lines) as a single channel. Video information is encoded on one channel, unlike the higher-quality S-Video (two channe ...
). This allows for full separation of the components. The signals are also time-compressed (with ratios of 3:2 for luminance and 3:1 for chrominance) and the two color difference signals are transmitted on alternate lines, further increasing compression. The color space was
YPbPr YPbPr or Y'PbPr, also written as , is a color space used in video electronics, in particular in reference to component video cables. YPBPR is gamma corrected YCBCR color space (it is not analog YUV that was used for analog TV, though component ...
, with a luminance component and red blue color difference chrominance components.


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 sub-carrier. * The MAC standard included a standard scrambling system, EuroCrypt, a precursor to the standard DVB-CSA encryption system


Technical details

In MAC color is encoded using the
YPbPr YPbPr or Y'PbPr, also written as , is a color space used in video electronics, in particular in reference to component video cables. YPBPR is gamma corrected YCBCR color space (it is not analog YUV that was used for analog TV, though component ...
color space. Luma (Y') is derived from red, green, and blue (R', G', B') after gamma-correction (formula similar to
PAL Phase Alternating Line (PAL) is a colour encoding system for analogue 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 ...
): * Y'= 0.2997R' + 0.587G' + 0.1145B' Color information is computed based on B-Y and R-Y differences, generating two compressed and weighted color-difference signals know in older MAC references as E' and E' or C and C. To avoid any confusion, and since the signals are analogue and bi-polar, these terms were replaced by P and P. P' and P' are used to transmit
chrominance Chrominance (''chroma'' or ''C'' for short) is the signal used in video systems to convey the color information of the picture (see YUV color model), separately from the accompanying luma signal (or Y' for short). Chrominance is usually represen ...
. On C-MAC, D-MAC and D2-MAC the following formulas apply: *P' = 0.733(B'-Y') *P' = 0.733(-0.299R'-0.587G'-0.886B') *P' = 0.2192R' -0.4303G' +0.6495B' *P' = 0.927(R'-Y') *P' = 0.927(0.701R'-0.587G'-0.114B') *P' = 0.6498R' -0.5441G' -0.1057B' Luminance signal range is -0.5 to 0.5 volts; color difference signals vary between -0.65 to 0.65 volts. The following table lists the main technical parameters of the various MAC variants:


MAC system innovations

Mathematical * A-MAC proved the mathematical principle that separating vision from colour for TV transmission was technologically viable. Broadcast engineering * The MAC audio subsystem is very 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 ...
, so much so that identical chip-sets are used. Broadcast engineering * D-MAC satellite broadcasts provided the first broadcast sourced
wide-screen Widescreen images are displayed within a set of aspect ratios (relationship of image width to height) used in film, television and computer screens. In film, a widescreen film is any film image with a width-to-height aspect ratio greater than t ...
television in Europe, and HD-MAC provided the first
HDTV High-definition television (HD or HDTV) describes a television system which provides a substantially higher image resolution than the previous generation of technologies. The term has been used since 1936; in more recent times, it refers to the g ...
broadcasts, in 1992.


Technical challenges

Although the MAC technique is capable of superior video quality, (similar to the improvement of component video over composite in a DVD player), its major drawback was that this quality was only ever realized when the video signals being transmitted remained in component form from source to transmitter. If at any stage the video had to be handled in composite form, the necessary encoding/decoding processes would severely degrade the picture quality. * Terrestrial TV broadcasters were never able to take full advantage of MAC image quality due to multiple interactions between their composite and component signal paths. * ''Direct to Home'' and TVRO broadcasters were able to take advantage of MAC's improved image quality because their studios and routing facilities were far less complex. * The success of
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 ...
audio for terrestrial television can be traced to the success of MAC technology. The MAC audio subsystem is nearly identical in design and function 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 ...
.


Countries and territories that used MAC

This is a list of nations that used the MAC standard for television broadcasting: * * * * * * *


Technological obsolescence

Since the vast majority of TV stations and similar installations were only wired for
composite video Composite video is an analog video signal format that carries standard-definition video (typically at 525 lines or 625 lines) as a single channel. Video information is encoded on one channel, unlike the higher-quality S-Video (two channe ...
, the fitting of a MAC transmitter at the end of the chain had the effect of degrading the transmitted image quality, rather than improving it. For this and other technical reasons, MAC systems never really caught on with broadcasters. MAC transmission technology was made obsolete by the radically new digital systems (like
DVB-T DVB-T, short for Digital Video Broadcasting – Terrestrial, is the DVB European-based consortium standard for the broadcast transmission of digital terrestrial television that was first published in 1997 and first broadcast in Singapore in Feb ...
and
ATSC Advanced Television Systems Committee (ATSC) standards are an American set of standards for digital television transmission over terrestrial, cable and satellite networks. It is largely a replacement for the analog NTSC standard and, like th ...
) in the late 1990s. Although MAC transmission systems are still used, the technology is obsolete. It is expected that MAC will cease to be used for TV transmission by 2012.


See also

TV transmission systems: * Analog high-definition television systems *
PAL Phase Alternating Line (PAL) is a colour encoding system for analogue 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 ...
, what MAC technology tried to replace *
SECAM SECAM, also written SÉCAM (, ''Séquentiel de couleur à mémoire'', French for ''color sequential with memory''), is an analog color television system that was used in France, some parts of Europe and Africa, and Russia. It was one of th ...
, what MAC technology tried to replace *
DVB-S Digital Video Broadcasting – Satellite (DVB-S) is the original DVB standard for Satellite Television and dates from 1995, in its first release, while development lasted from 1993 to 1997. The first commercial applications was by Star TV in Asia ...
, MAC technology was replaced by this standard *
DVB-T DVB-T, short for Digital Video Broadcasting – Terrestrial, is the DVB European-based consortium standard for the broadcast transmission of digital terrestrial television that was first published in 1997 and first broadcast in Singapore in Feb ...
, MAC technology was replaced by this standard


References


External links


Multiplexed Analogue Components
in "Analog TV Broadcast Systems" by Paul Schlyter
IBA Engineering Announcement broadcast 3 February 1987
with more information on MAC {{High-definition High-definition television Satellite television Television transmission standards Television technology British inventions 1982 introductions Audiovisual introductions in 1982