SECAM

NTSCPAL or PAL/SECAMSECAMNo informationDistribution of analog TV systems in the world.

SECAM stands for Séquentiel Couleur à Mémoire, French for "Sequential Color with Memory". It is a system for codifying analog color television used for the first time in France. The Secam system was invented by a team led by French engineer and inventor Henri Georges de France working for the Thomson firm. It is, historically, the first European color television standard.

Technical details

SECAM analogue television signal spectrum under French Standard L.

SECAM makes use of the YDrDb color space, which is a scaled version of YUV, to encode the chrominance information represented by Dr and Db. It differs from the other color systems, firstly, in that SECAM uses frequency modulation to encode the chrominance information onto two separate subcarriers, and secondly, instead of transmitting the two color information signals together, only it sends one of them at a time, and also uses the information about the other color of the preceding line. To do this, an analog delay line is used, as a memory device, to store a line of color information. This justifies its name. from "sequential with memory" (although you could also say that it uses an analog buffer).

Chrominance signals are defined as follows:

${displaystyle left{begin{array}{lcr}Dr fake= fake-1 e.g.*(R-Y)Db fake= stranger1.505*(B-Y)end{array}}}{right. !$

Because SECAM transmits only one color at a time, it is free from the color artifacts present in NTSC and PAL standards resulting from the combined transmission of both signals, which means that the vertical color resolution is reduced to half compared to the NTSC standard.

Frequency modulation of the color information allows SECAM to be completely free of the dot-shift problem commonly found with other analog standards. SECAM transmissions are more robust over longer distances than NTSC or PAL. However, due to its frequency modulation nature, the color signal is still present, albeit at reduced amplitude, even in black and white parts of the image, thus being subject to stronger color crosstalk despite the fact that there is no color tracking of the type of the PAL standard.

History

Work on SECAM began in 1956 when the system was patented by Henri Georges de France under various French and US patents, including number 2993086. The technology was ready by the late 1950s, but this was too soon for a comprehensive introduction. Initially, a version of SECAM was devised and tested for the 819-line French monochrome television standard, today known as ITU Standard E, but was not introduced, due to a pan-European agreement to introduce color TV on 625 lines only, of which The French government of the time was signatory. As a result, France had to initiate the conversion by switching to a 625-line monochrome television system, which occurred in the early 1960s with the introduction of a second television network. The first proposed color system was called SECAM I in 1961, followed by further studies to improve compatibility and image quality over the 625-line standard. Subsequent improvements were named SECAM II and SECAM III, the latter being presented in 1965 at the CCIR General Assembly in Vienna.

Subsequent improvements were SECAM III A and SECAM III B, which was the system adopted for general use in France in 1967. Soviet technicians were involved in the development of the standard, and even created their own incompatible variant called NIIR or SECAM IV, which was not implemented. The team was working at the Telecentrum in Moscow under the direction of Soviet scientist Pavel Vasilievich Shmakov. The designation NIIR comes from the transliteration of Научно-исследовательский институт радио (Nauchno-issledovatel'skiy institut radio., Radio Research and Development Institute, in Spanish) who participated in the development. Two standards were developed: Nonlinear NIIR, which uses a procedure analogous to gamma correction, and Linear NIIR or SECAM IV which omits this process.

Broadcasting with the SECAM standard was inaugurated in France on October 1, 1967, on the Second Channel, today known as France 2. On the day of the inauguration, a group of four men led by Georges Gorse, Minister of Information at the time and three collaborators in the development of the system, was in a television studio. After a countdown, at 2:15 p.m. m. French time, the original black and white image was switched to color and the presenter then declared "Et voici la couleur!" (In Spanish: And here is the color!). In 1967, the Compagnie de Télévision du Liban et du Proche (in Spanish: Television Company of Lebanon and the East) became the third television channel in the world after the Soviet Union and France to broadcast in color, using SECAM technology.

The first color televisions cost 5,000 francs. Color television was not very popular initially; only about 1,500 people watched the inaugural program in color. A year later, only 200,000 receivers had been sold out of an expected million. This pattern was similar to the slow acceptance of color television in the United States.

SECAM was later adopted by the former French and Belgian colonies, Greece, the Soviet Union and Eastern Bloc countries (except Romania and Albania), and Middle Eastern countries. However, with the fall of the communist regimes, and after a period in which multi-standard TV sets became a commodity, many Eastern European countries decided to switch to the PAL standard. Other countries, notably the UK and Italy, briefly experimented with SECAM before turning to PAL. In Colombia, in 1966 the first tests for color television transmission with the SECAM standard began, however years later this standard was abandoned for NTSC and PAL (used together until the late 90s, when the standard was unanimously adopted). first.

Development

Some have argued that the main motivation for the development of SECAM in France was to protect local television equipment manufacturers. However, the incompatibility had started with the unusual decision to adopt positive video modulation for French broadcast signals. Earlier systems like System A and 819 line systems were the only other systems to use positive video modulation. Furthermore, the development of SECAM predates that of PAL. NTSC is considered undesirable in Europe due to its color cast problem that requires additional control, which in the SECAM and PAL standards were resolved.

Unlike other manufacturers, the company where SECAM was invented, Technicolor (known as Thomson until 2010), continues to sell televisions around the world under different brand names; this may be due in part to the inheritance of SECAM. Thomson bought the company that developed PAL, Telefunken, and today it even co-owns the RCA brand, creator of NTSC. Thomson is also a co-author of the American ATSC digital television standard.

Varieties of SECAM

There are six varieties of SECAM:

• SECAM L-L': It was used only in France, Luxembourg and Monaco in southern France. It was replaced in 2011 by the DVB-T digital standard.
• SECAM B/G: It was used in Saudi Arabia, Egypt, Iran, Libya, Morocco and Tunisia, which changed to the PAL standard and currently do so towards the DVB-T digital norm or DVB-T2.
• SECAM D/K: It is used in the Commonwealth of Independent States and in parts of Eastern Europe, although most of the countries of this area migrated to the PAL standard and currently do so to the DVB-T or DVB-T2 standard for Russia.
• SECAM H: System variant introduced around 1983-1984, for the addition of teletext information.
• SECAM K: Variant introduced for the French units. However, the SECAM standard used in France's overseas possessions, as well as the African countries that were French colonies, slightly differs from the SECAM of France.
• SECAM M: Used between 1970-1991 in Cambodia and Vietnam (Hanoi and northern cities).