SÉCAM (Séquentiel couleur avec mémoire, French for "sequential colour with memory") is an analog color television system first used in France. SÉCAM was invented by a team led by Henri de France and working at Thomson. It is historically the first European color television standard. Analog television encodes picture information by varying the voltages and/or frequency of the signal. ... Henri de France was an influential French television engineer. ... Thomson SA (NYSE: TMS)(Euronext: TMM) , formerly known as Thomson Multimedia is a multinational electronics manufacturer and media services provider headquartered in Boulogne, France. ... World map showing location of Europe A satellite composite image of Europe Europe is geologically and geographically a peninsula, forming the westernmost part of Eurasia. ...

Technical details

Just as the other color standards adopted for broadcast usage over the world, SÉCAM is a compatible standard, which means that monochrome television receivers predating its introduction are still able to correctly show the programs, although only in black and white. Because of this compatibility requirement, colour standards add a second signal to the basic monochrome signal, and this signal carries the colour information, called chrominance or C in short, while the black and white information is called the luminance (Y in short). Old TV receivers only see the luminance, while colour receivers process both signals. Georges Valensi was a French telecommunications engineer who, in 1938, invented and patented a method of transmitting color images so that they could be received on both color and black & white television sets. ... Chrominance (chroma for short) comprises the two components of a television signal that encode color information. ... The word luminance, a synonym for luminosity, means emitting or reflecting light. ...

Another aspect of the compatibility being not using more bandwidth than the monochrome signal alone, the colour signal has to be somehow inserted into the monochrome signal, without disturbing it. This insertion is possible because the spectrum of the monochrome TV signal is not continuous, hence empty space exists, which can be recycled. This lack of continuity results from the discrete nature of the signal, which is divided into frames and lines. Analog colour systems differ by the way in which empty space is used. In all cases, the colour signal is inserted at the end of the spectrum of the monochrome signal.

In order to be able to separate the colour signal from the monochrome one in the receiver, a fixed frequency subcarrier has to be used, this subcarrier being modulated by the colour signal.

The colour space is three dimensional by the nature of the human vision, so after subtracting the luminance, which is carried by the base signal, the colour subcarrier still has to carry a two dimensional signal. Typically the red (R) and the blue (B) information are carried because their signal difference with luminance (R-Y and B-Y) is stronger than that of green (G-Y).

SÉCAM differs from the other colour systems by the way the R-Y and B-Y signals are carried.

First, SÉCAM uses frequency modulation to encode chrominance information on the subcarrier. Frequency modulation (FM) is a form of modulation which represents information as variations in the instantaneous frequency of a carrier wave. ... Chrominance (chroma for short) comprises the two components of a television signal that encode color information. ...

Second, instead of transmitting the red and blue information together, it only sends one of them at a time, and uses the information about the other colour from the preceding line. It uses a delay line, an analog memory device, for the purpose of storing one line of colour information. This justifies the "Sequential, With Memory" name.

Because SÉCAM transmits only one colour at a time, it is free of the colour artifacts present in NTSC and PAL and resulting from the combined transmission of both signals.

This means that the vertical colour resolution is halved relative to NTSC. It is however not halved compared to PAL. Although PAL does not eliminate half of vertical colour information during encoding, it combines colour information from adjacent lines at the decoding stage, in order to compensate for colour subcarrier phase errors occurring during the transmission of the Amplitude-Modulated colour subcarrier. This is normally done using a delay line borrowed from SÉCAM (the result is called PAL DL or PAL Delay-Line, sometimes interpreted as DeLuxe), but can be accomplished "visually" in cheap TV sets (PAL standard). Because the FM modulation of SÉCAM's colour subcarrier is insensitive to phase (or amplitude) errors, phase errors do not cause loss of colour saturation in SÉCAM, although they do in PAL. In NTSC such errors cause colour shifts. NTSC is the analog television system in use in the United States and many other countries, including most of the Americas and some parts of East Asia. ... For other meanings of PAL see PAL (disambiguation). ...

The colour difference signals in SÉCAM are actually calculated in the YDbDr colour space, which is a scaled version of the YUV colour space. This encoding is better suitable to the transmission of only one signal at a time. YDbDr is the colour space used in the SECAM colour television broadcasting standard, which is used in France and some countries of the former Eastern Bloc. ... A color model is an abstract mathematical model describing the way colors can be represented as tuples of numbers, typically as three or four values or color components (e. ... Example of U-V color plane, Y value = 0. ...

FM modulation of the colour information allows SÉCAM to be free of the dot crawl problem commonly encountered with the other analog standards and first widely noticed with the Laserdiscs. Dot crawl can be removed from PAL and NTSC-encoded signals using a comb filter. Such filters are usually only included in high-end displays. Dot crawl patterns (animated checkerboard) are easily visible along vertical lines in DVD menus displayed even by expensive (eg. plasma) displays if these displays are connected to a signal source (DVD player) using a composite PAL or NTSC connection rather than for example RGB. The dot crawl is the popular name for a visual defect of color analog video standards when signals are transmitted as composite video. ... Pioneers LaserDisc Logo The Laserdisc (LD) was the first commercial optical disc storage medium, and was used primarily for the presentation of movies. ... In signal processing, a comb filter adds a slightly delayed version of a signal to itself, causing phase cancellations and a spectrum that looks like a comb. ...

The idea of reducing the vertical colour resolution comes from Henri de France, who observed that colour information is approximately identical for two successive lines. Because the colour information was designed to be a cheap, backwards-compatible addition to the monochrome signal, the colour signal has a lower bandwidth than the luminance signal, and hence lower horizontal resolution. Fortunately, the human visual system is similar in design: it perceives changes in luminance at a higher resolution than changes in chrominance, so this asymmetry has minimal visual impact. It was therefore also logical to reduce the vertical colour resolution. Henri de France was an influential French television engineer. ...

DVD and other digital television formats have continued to exploit this visual artefact, subsampling colour both horizontally and vertically. Hence, paradoxically, VHS NTSC videos can have a greater vertical colour resolution than DVD. DVD is an optical disc storage media format that can be used for storing data, including movies with high video and sound quality. ... Top view VHS cassette with US Quarter for scale Bottom view of VHS cassette with magnetic tape exposed The Video Home System, better known by its acronym VHS, is a recording and playing standard for video cassette recorders (VCRs), developed by JVC (ironically, with some of its critical technology under... NTSC is the analog television system in use in the United States and many other countries, including most of the Americas and some parts of East Asia. ... DVD is an optical disc storage media format that can be used for storing data, including movies with high video and sound quality. ...

A similar paradox applies to the vertical resolution in television in general: reducing the bandwidth of the video signal will preserve the vertical resolution, even if the image loses sharpness and is smudged in the horizontal direction. Hence, video could be sharper vertically than horizontally. However, because of the interlacing, vertical resolution is effectively not as great as the number of scan lines. Additionally, transmitting an image with too much vertical detail will cause annoying flicker on television screens, as small details will only appear on a single line, and hence be refreshed at half the frequency. Computer-generated text and inserts have to be carefully low-pass filtered to prevent this.

History

Work on SÉCAM began in 1956. The technology was ready by the end of the fifties, but this was too soon for a wide introduction. Notably, SÉCAM did not work with the 819-line television standard then used by the then sole French TV network. France had to start the conversion by switching over to a 625-line television standard, which happened at the beginning of the sixties with the introduction of a second network. 1956 was a leap year starting on Sunday. ...

SÉCAM was inaugurated in France on October 1st, 1967, on la seconde chaîne (the second network), currently called France 2. A group of four men, all dressed in suits, presumably presenters and network officials, were shown standing in a studio. The image was originally black and white and suddenly switched to colour; one of the people said something along the lines of "now you can see us as we really are". October 1 is the 274th day of the year (275th in Leap years). ... 1967 was a common year starting on Sunday (the link is to a full 1967 calendar). ...

The first colour television sets cost 5000 Francs. Colour TV was not very popular initially; only about 1500 people watched the inaugural program in colour. A year later, only 200,000 sets had been sold of an expected million. This pattern was similar to the earlier slow build-up of colour television popularity in the USA.

SÉCAM was later adopted by former French and Belgian colonies, Eastern European countries, the former Soviet Union and Middle Eastern countries. However, with the fall of communism, and following a period when multi-standard TV sets became a commodity, a lot of Eastern European countries decided to switch to PAL. Eastern Europe is, by convention, that part of Europe from the Ural and Caucasus mountains in the East to an arbitrarily chosen boundary in the West. ... A map showing countries commonly considered to be part of the Middle East The Middle East is a region comprising the lands around the southern and eastern parts of the Mediterranean Sea, a territory that extends from the eastern Mediterranean Sea to the Persian Gulf. ... The word commodity is a term with distinct meanings in business and in Marxist political economy. ...

Why SÉCAM in France?

Some have argued that the primary motivation for the development of SÉCAM in France was to protect French television equipment manufacturers. However, incompatibility had started with the earlier decision to uniquely adopt positive video modulation for French broadcast signals. Also, SÉCAM development predates PAL; and because of frame rate differences (50 versus 60 Hz) and the requirement for compatibility with monochrome TV receivers, it was not possible for Europeans to adopt NTSC. SÉCAM and PAL addressed the chroma phase problem, whereas NTSC required the tint control on U.S. sets. In Amplitude Modulated (AM) broadcast analogue television systems it is possible to modulate the video signal two ways. ... NTSC is the analog television system in use in the United States and many other countries, including most of the Americas and some parts of East Asia. ... Since the NTSC color television standard is susceptible to color errors, there is a tint control on NTSC television sets, which allows the image hue to be corrected. ...

Nonetheless, SÉCAM was partly developed for reasons of national pride. Henri de France's personal charisma and ambition may have been a contributing factor. The word charisma (from the Greek word charis) or gift, is often used in this form to describe an ability to charm or influence people. ...

Unlike some other manufacturers, the company where SÉCAM was invented, Thomson, still sells TV sets worldwide under different brands; this may be due in part to the legacy of SÉCAM. Thomson bought the company which developed PAL, Telefunken, and today even co-owns the RCA brand —RCA being the creator of NTSC. Thomson also co-authored the current American high-definition TV standard ATSC. Thomson SA (NYSE: TMS)(Euronext: TMM) , formerly known as Thomson Multimedia is a multinational electronics manufacturer and media services provider headquartered in Boulogne, France. ... Telefunken is a German radio- and television company, founded in 1903. ... RCA, formerly an initialism for the Radio Corporation of America, is now a trademark used by two companies for products descended from that common ancestor: Thomson Consumer Electronics, which manufactures RCA-branded televisions, DVD players, video cassette recorders, direct broadcast satellite decoders, camcorders, audio equipment, telephones, and related accessories; and... The Advanced Television Systems Committee (ATSC) is the group that helped to develop the new digital television standard for the United States, also adopted by Canada, Mexico and South Korea and being considered by other countries. ...

Why SÉCAM elsewhere?

The adoption of SÉCAM in Eastern Europe has been attributed to Cold War political machinations: it has been claimed that its use made it impossible for most Eastern Europeans to view television broadcast from outside the Iron Curtain using PAL. A cold war is a state of conflict between nations that does not involve direct military action but is pursued primarily through economic and political actions, acts of espionage or conflict through surrogates. ... In the summer of 1989, the foreign ministers of Austria and Hungary, Alois Mock and Gyula Horn, ceremoniously cut through the border defences separating their countries. ...

However, remember that PAL and SÉCAM are just standards for the colour subcarrier, used in conjunction with older standards for the base monochrome signals. The names for these monochrome standards are letters, such as M, B/G, D/K, and L. See CCIR, OIRT and FCC (the standardization bodies). The ITU Radiocommunication Sector (ITU-R) is a standards body subcommittee of the International Telecommunication Union relating to radio communication. ... The International Radio and Television Organisation (official name in French: Organisation Internationale de Radiodiffusion et de Télévision or OIRT), more often called Intervision (Russian Интервидение, Polish Interwizja), was an East European network of radio and television broadcasters established in 1946 with the primary purpose of exchanging productions between its members. ... The Federal Communications Commission (FCC) is an independent United States government agency, created, directed, and empowered by Congressional statute. ...

These signals are much more important to compatibility than the colour subcarriers. They differ by AM or FM modulation, signal polarisation, relative frequencies within the channel, bandwidth, etc. For example, a PAL D/K TV set will be able to receive a SÉCAM D/K signal (although in black and white), while it will not be able to receive a PAL B/G signal at all. So even before SÉCAM came to Eastern European countries, most viewers could not have received Western programs —and colour TV sets were not exactly widespread in the Communist bloc anyway, so the B/W-only reception wasn't actually much of a problem. Amplitude modulation (AM) is a form of modulation in which the amplitude of a carrier wave is varied in direct proportion to that of a modulating signal. ... Frequency modulation (FM) is a form of modulation which represents information as variations in the instantaneous frequency of a carrier wave. ... This article treats polarization in electrodynamics. ...

Another, speculative political theory is that PAL was originally German, while SÉCAM came from a country which had better political relations with Eastern Europe after the war. Mushroom cloud from the nuclear explosion over Nagasaki rising 18 km into the air. ...

SÉCAM varieties

There are three varieties of SÉCAM:

1. French SÉCAM, used in France and its former colonies
2. MESÉCAM, used in the Middle East
3. SÉCAM D/K, used in the Commonwealth of Independent States and Eastern Europe (this is simply SÉCAM used with the D and K monochrome TV transmission standards).

Around 1983-1984 a new colour identification standard has been introduced in order to make more space available inside the signal for adding teletext information (originally according to the Antiope standard). Identification bursts have been made per-line (like in PAL) rather than per-picture. Older SÉCAM TV sets might not be able to display colour for today's broadcasts. A map showing countries commonly considered to be part of the Middle East The Middle East is a region comprising the lands around the southern and eastern parts of the Mediterranean Sea, a territory that extends from the eastern Mediterranean Sea to the Persian Gulf. ... The Commonwealth of Independent States (CIS) (in Russian: Содружество Независимых Государств (СНГ) - Sodruzhestvo Nezavisimykh Gosudarstv) is a confederation or alliance consisting of 11 of the 15 former Soviet Republics, the exceptions being the three Baltic states: Estonia, Latvia, and Lithuania, and Georgia. ... Teletext is an information retrieval service provided by television broadcast companies. ... This article is about a teletext system, for other things and people named Antiope, see Antiope (disambiguation). ...

Problems with the standard

Unlike PAL or NTSC, analog SÉCAM television cannot easily be edited in its native analog form. Because of the frequency modulation usage, SÉCAM is not linear with respect to the input image (this is also what protects it against broadcasting distorsions), so electrically mixing two (synchronized) SÉCAM signals does not yield a valid SÉCAM signal, unlike with analog PAL or NTSC. For this reason, to mix two SÉCAM signals, they must be demodulated, have the mix applied to the demodulated signals, and be remodulated again. Hence, post-production is often done in PAL, or in component formats, with the result encoded or transcoded into SÉCAM at the point of transmission. Reducing the costs of running television stations is one reason for some countries' recent switchovers to PAL. Post production is the general term for the last stage of film production in which photographed scenes (also called footage) are put together into a complete film. ...

TVs currently sold in SÉCAM countries support both SÉCAM and PAL, and more recently baseband NTSC as well (though not usually broadcast NTSC, ie. they cannot accept an antenna signal). Although the older analog camcorders (VHS, VHS-C) were produced in SÉCAM versions, none of the 8 mm or Hi-band models (S-VHS, S-VHS-C and Hi-8) recorded it directly. Instead, a SÉCAM to PAL converter was used internally. The result could be converted back to SÉCAM in some models; most people buying such expensive equipment would have a multistandard TV set anyway and not need such a conversion. Digital camcorders or DVD players do not accept or output a SÉCAM analog signal. However, this is of dwindling importance: since 1980 most European domestic video equipment uses SCART connectors, allowing the transmission of RGB signals between devices. This eliminates the legacy of PAL, SÉCAM and NTSC colour subcarrier standards. For other meanings of PAL see PAL (disambiguation). ... In telecommunication, the term baseband has the following meanings: 1. ... NTSC is the analog television system in use in the United States and many other countries, including most of the Americas and some parts of East Asia. ... Broadcast could refer to: Broadcast, an electronica musical group broadcasting, the distribution of audio and video signals Broadcast address, an IP address allowing information to be sent to all machines on a given subnet. ... Top view VHS cassette with US Quarter for scale Bottom view of VHS cassette with magnetic tape exposed The Video Home System, better known by its acronym VHS, is a recording and playing standard for video cassette recorders (VCRs), developed by JVC (ironically, with some of its critical technology under... VHS-C is the compact VHS format used for portable video recorders. ... 8mm may be referring to: 8mm film, or its replacement American film entitled 8mm about a private detective verifying the existence of a snuff movie. ... S-VHS or Super VHS was an improved, backward-compatible version of the VHS standard for domestic video cassette recorders. ... VHS-C is the compact VHS format used for portable video recorders. ... A 8mm Camcorder The 8mm Video Format (official name: Video8) is a type of video cassette recorder and video tape. ... 1980 is a leap year starting on Tuesday. ... SCART plug SCART (from Syndicat des Constructeurs dAppareils Radiorécepteurs et Téléviseurs) is a French-originated standard and associated 21-pin connector for connecting audio and video equipment to television sets. ... The RGB color model utilizes the additive model in which red, green, and blue light are combined in various ways to create other colors. ...

In general, modern professional equipment is now all-digital, and uses component-based digital interconnects such as CCIR 601 to eliminate the need for any analog processing prior to the final modulation of the analog signal for broadcast. However large installed bases of analog professional equipment still exist, particularly in third world countries. CCIR 601 is the old name of a standard published by the CCIR (now ITU-R) for encoding interlaced analogue video signals in digital form. ...

Facetious interpretations of the SÉCAM acronym

American engineers have been known to claim that SÉCAM stands for "System Essentially Contrary to the American Method". Likewise, given that the French often take a stance against what they call American cultural imperialism, in favour of French culture, SÉCAM is jokingly said to also stand for "Système Élégant Contre les Américains" (Elegant system against the Americans). European non-SÉCAM countries know that it really means "Shows Every Colour All Murky" — a reference to the reduction in vertical colour resolution. Although the facetious expansions referencing the American system may have reflected the intentions of the SÉCAM designers, the last one is (as a contrast with PAL) probably a mistake.

Countries and territories which use or have used SÉCAM

bright green - NTSC, yellow - PAL, orange - SECAM, grey - no information

Afghanistan, Andorra, Armenia, Azerbaijan, Belarus, Benin, Bulgaria, Burkina Faso, Burundi, Cambodia (Kampuchea), Central African Republic, Chad, Congo (People's Republic), Côte d'Ivoire, Czech Republic, Djibouti, East Germany, Egypt, Equatorial Guinea, Estonia, France, French Guiana, French Polynesia, Gabon, Georgia, Greece, Guadeloupe, Hungary, Iran, Iraq, Kazakhstan, North Korea, Kyrgyzstan, Latvia, Libya, Lithuania, Luxembourg, Madagascar, Mali, Martinique, Mauritania, Mauritius, Monaco, Mongolia, Morocco, New Caledonia, Niger, North Korea, Poland, Réunion, Romania, Russia, Rwanda, Saint-Pierre and Miquelon, Saudi Arabia, Senegal, Serbia, Slovakia, Syria, Tahiti, Tajikistan, Togo, Tunisia, Turkmenistan, Ukraine, Uzbekistan, Vietnam, Wallis Island, Zaire. Download high resolution version (1276x822, 58 KB) information from sources: [1], [2], NTSC, PAL, SECAM File links The following pages link to this file: NTSC PAL SÉCAM Categories: GFDL images ... Download high resolution version (1276x822, 58 KB) information from sources: [1], [2], NTSC, PAL, SECAM File links The following pages link to this file: NTSC PAL SÉCAM Categories: GFDL images ... Côte dIvoire (often called Ivory Coast in English; see below about the name) is a country in West Africa. ... East Germany, officially the German Democratic Republic (GDR), German Deutsche Demokratische Republik (DDR), was a Communist state that existed from 1949 to 1990 in the former Soviet occupation zone of Germany. ... Réunion is an island, as well as an overseas département (département doutre-mer, or DOM) of France, located in the Indian Ocean, east of Madagascar, about 200 km southwest of Mauritius. ... Saint-Pierre and Miquelon (French Saint-Pierre et Miquelon) is a French overseas collectivity consisting of several small islands off the eastern coast of Canada near Newfoundland. ... Serbia and Montenegro  – Serbia    – Kosovo and Metohia        (UN administration)    – Vojvodina  – Montenegro Official language Serbian1 Capital Belgrade Area  – Total  – % water  88,361 km²  n/a Population  – Total (2002)     (without Kosovo)  – Density  7. ... Tahiti is the largest island in French Polynesia, located in the archipelago of Society Islands in the southern Pacific Ocean, at 17° 40 South, 149° 30 West. ...

Some SÉCAM countries are in the process of switching to PAL and are broadcasting in both SÉCAM and PAL formats. The list does not contain certain countries known to have totally switched to PAL. For other meanings of PAL see PAL (disambiguation). ...

See also

• Broadcast television systems

There are several broadcast television systems in use in the world today. ...

External link

• http://www.nmia.com/~roberts/vidstd