Phase Alternating Line (PAL) is a colour encoding system foranalog television. It was one of three major analogue colour television standards, the others beingNTSC andSECAM. In most countries it was broadcast at625 lines, 50 fields (25 frames) per second, and associated with CCIR analoguebroadcast television systemsB,D,G,H,I orK. The articles on analogbroadcast television systems further describeframe rates,image resolution, and audio modulation.
PAL video iscomposite video becauseluminance (luma, monochrome image) andchrominance (chroma, colour applied to the monochrome image) are transmitted together as one signal. A latter evolution of the standard,PALplus, added support forwidescreen broadcasts with no loss of verticalimage resolution, while retaining compatibility with existing sets. Almost all of the countries using PAL are currently in theprocess of conversion, or have already converted transmission standards toDVB,ISDB orDTMB. The PAL designation continues to be used in some non-broadcast contexts, especially regardingconsole video games.
PAL was adopted by most European countries, by several African countries, byArgentina,Brazil,Paraguay,Uruguay, and by most ofAsia Pacific (including the Middle East and South Asia).[1] Countries in those regions that did not adopt PAL wereFrance,[2] Francophone Africa,[2] several ex-Soviet states,[2]Japan,[3]South Korea,Liberia,Myanmar, thePhilippines,[3] andTaiwan.[3]
With the introduction ofhome video releases and later digital sources (e.g.DVD-Video), the name "PAL" might be used to refer to digital formats, even though they use completely different colour encoding systems. For instance,576i (576 interlaced lines) digital video with colour encoded asYCbCr, intended to be backward compatible and easily displayed on legacy PAL devices, is usually mentioned as "PAL" (eg: "PAL DVD"). Likewise, video game consoles outputting a 50 Hz signal might be labeled as "PAL", as opposed to 60 Hz on NTSC machines. These designations should not be confused with the analog colour system itself.
In the 1950s, the Western European countries began plans to introduce colour television, and were faced with the problem that theNTSC standard demonstrated several weaknesses, including colour tone shifting under poor transmission conditions, which became a major issue considering Europe's geographical and weather-related particularities. To overcome NTSC's shortcomings, alternative standards were devised, resulting in the development of the PAL and SECAM standards. The goal was to provide a colour TV standard for the European picture frequency of 50 fields per second (50 hertz), and finding a way to eliminate the problems with NTSC.
PAL was developed byWalter Bruch atTelefunken inHanover,West Germany, with important input fromGerhard Mahler [de].[4] The format was patented byTelefunken in December 1962, citing Bruch as inventor,[5][6] and unveiled to members of theEuropean Broadcasting Union (EBU) on 3 January 1963.[6] When asked why the system was named "PAL" and not "Bruch", the inventor answered that a "Bruch system" would probably not have sold very well ("Bruch" is the German word for "breakage"[7]).
The first broadcasts began in theUnited Kingdom in July 1967, followed byWest Germany at theBerlin IFA on August 25.[6][8] The BBC channel initially using the broadcast standard wasBBC2, which had been the first UK TV service to introduce "625-lines" during 1964. TheNetherlands andSwitzerland started PAL broadcasts by 1968, withAustria following the next year.[6]
Telefunken PALcolour 708T[9] was the first PAL commercial TV set. It was followed byLoewe-Farbfernseher S 920 andF 900.[10]
Telefunken was later bought by the French electronics manufacturerThomson. Thomson also bought theCompagnie Générale de Télévision whereHenri de France developed SECAM, the firstEuropean Standard for colour television. Thomson, now called Technicolour SA, also owns theRCA brand and licences it to other companies;Radio Corporation of America, the originator of that brand, created the NTSC colour TV standard before Thomson became involved.
InItaly, at firstIndesit in co-operation with SEIMART tried to develop its own standard, ISA (Identificazione a Soppressione Alternata). However, while it presented very interesting technical and qualitative characteristics, it arrived too late and its eventual adoption would have resulted in heavy political and economic consequences, therefore the system was abandoned in favor of PAL in 1975.[11][12]
TheSoviets developed two further systems, mixing concepts from PAL and SECAM, known as TRIPAL and NIIR, that never went beyond tests.[6]
In 1993,[13] an evolution of PAL aimed to improve and enhance format by allowing16:9aspect ratio broadcasts, while remaining compatible with existing television receivers,[14] was introduced. NamedPALplus, it was defined byITU recommendation BT.1197-1. It was developed at theUniversity of Dortmund inGermany, in cooperation with German terrestrial broadcasters and European and Japanese manufacturers. Adoption was limited to European countries.
With the introduction ofdigital broadcasts and signal sources (ex:DVDs, game consoles), the term PAL was used imprecisely to refer to the625-line/50 Hz television system in general, to differentiate from the525-line/60 Hz system generally used with NTSC. For example, DVDs were labelled as PAL or NTSC (referring to the line count and frame rate)[15] even though technically the discs carry neither PAL nor NTSC encoded signal. These devices would still have analog outputs (ex;composite video output), and would convert the digital signals (576i or480i) to the analog standards to assure compatibility. CCIR 625/50 and EIA 525/60 are the proper names for these (line count and field rate) standards; PAL and NTSC on the other hand are methods of encoding colour information in the signal.
"PAL-D", "PAL-N", "PAL-H" and "PAL-K" designations on this section describe PAL decoding methods and are unrelated tobroadcast systems with similar names.[6]
The Telefunken licence covered any decoding method that relied on the alternating subcarrier phase to reduce phase errors, described as "PAL-D" for "delay", and "PAL-N" for "new" or "Chrominance Lock".[6]
This excluded very basic PAL decoders that relied on the human eye to average out the odd/even line phase errors, and in the early 1970s some Japanese set manufacturers developed basic decoding systems to avoid paying royalties toTelefunken. These variations are known as "PAL-S" (for "simple" or "Volks-PAL"),[16] operating without a delay line and suffering from the “Hanover bars” effect. An example of this solution is theKuba Porta Color CK211P set.[6] Another solution was to use a 1Hanalogue delay line to allow decoding of only the odd or even lines. For example, the chrominance on odd lines would be switched directly through to the decoder and also be stored in the delay line. Then, on even lines, the stored odd line would be decoded again. This method (known as 'gated NTSC') was adopted bySony on their 1970sTrinitron sets (KV-1300UB toKV-1330UB), and came in two versions: "PAL-H" and "PAL-K" (averaging over multiple lines).[6][16] It effectively treated PAL as NTSC, suffering from hue errors and other problems inherent in NTSC and required the addition of a manualhue control.
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Most PAL systems encode the colour information using a variant of theY'UV colour space.comprises the monochromeluma signal, with the three RGB colour channels mixed down onto two, and.
Like NTSC, PAL uses aquadrature amplitude modulatedsubcarrier carrying thechrominance information added to the luma video signal to form acomposite video baseband signal. The frequency of this subcarrier is 4.43361875 MHz for PAL 4.43, compared to 3.579545 MHz for NTSC 3.58. The SECAM system, on the other hand, uses a frequency modulation scheme on its two line alternate colour subcarriers 4.25000 and 4.40625 MHz.
The name "Phase Alternating Line" describes the way that the phase of part of the colour information on the video signal is reversed with each line, which automatically corrects phase errors in the transmission of the signal by cancelling them out, at the expense of vertical frame colour resolution. Lines where the colour phase is reversed compared to NTSC are often called PAL or phase-alternation lines, which justifies one of the expansions of the acronym, while the other lines are called NTSC lines. Early PAL receivers relied on the human eye to do that cancelling; however, this resulted in a comb-like effect known asHanover bars on larger phase errors. Thus, most receivers now use a chrominanceanalogue delay line, which stores the received colour information on each line of display; an average of the colour information from the previous line and the current line is then used to drive thepicture tube. The effect is that phase errors result insaturation changes, which are less objectionable than the equivalent hue changes of NTSC. A minor drawback is that the vertical colour resolution is poorer than the NTSC system's, but since the human eye also has a colour resolution that is much lower than its brightness resolution, this effect is not visible. In any case, NTSC, PAL, and SECAM all have chrominance bandwidth (horizontal colour detail) reduced greatly compared to the luma signal.
_and_line_(64%25C2%25B5s)_decoding.jpg)
The 4.43361875 MHz frequency of the colour carrier is a result of 283.75 colour clock cycles per line plus a 25 Hz offset to avoid interferences. Since the line frequency (number of lines per second) is 15625 Hz (625 lines × 50 Hz ÷ 2), the colourcarrier frequency calculates as follows: 4.43361875 MHz = 283.75 × 15625 Hz + 25 Hz.
The frequency 50 Hz is the optional refresh frequency of the monitor to be able to create an illusion of motion, while 625 lines means the vertical lines or resolution that the PAL system supports.
The original colourcarrier is required by the colour decoder to recreate thecolour difference signals. Since the carrier is not transmitted with the video information it has to be generated locally in the receiver. In order that thephase of this locally generated signal can match the transmitted information, a 10 cycle burst of coloursubcarrier is added to the video signal shortly after the line sync pulse, but before the picture information, during the so-calledback porch. This colour burst is not actually in phase with the original colour subcarrier, but leads it by 45 degrees on the odd lines and lags it by 45 degrees on the even lines. Thisswinging burst enables the colour decoder circuitry to distinguish the phase of thevector which reverses every line.
For PAL-B/G the signal has these characteristics.
| Parameter | Value |
|---|---|
| Bandwidth | 5 MHz[1] |
| Horizontal sync polarity | Negative |
| Total time for each line | 64 μs[17][18] |
| Front porch (A) | 1.65+0.4 −0.1 μs |
| Sync pulse length (B) | 4.7±0.20 μs |
| Back porch (C) | 5.7±0.20 μs |
| Active video (D) | 51.95+0.4 −0.1 μs |
(Total horizontal sync time 12.05 μs)
After 0.9 μs a2.25±0.23 μscolourburst of10±1 cycles is sent. Most rise/fall times are in250±50 ns range. Amplitude is 100% for white level, 30% for black, and 0% for sync.[17]
TheCVBS electrical amplitude is Vpp1.0 V and impedance of 75Ω.[19]
The vertical timings are:
| Parameter | Value |
|---|---|
| Vertical lines | 312.5 (625 total) |
| Vertical lines visible | 288 (576 total) |
| Vertical sync polarity | Negative (burst) |
| Vertical frequency | 50 Hz |
| Sync pulse length (F) | 0.576 ms (burst)[20] |
| Active video (H) | 18.4 ms |
(Total vertical sync time 1.6 ms)
As PAL is interlaced, every two fields are summed to make a complete picture frame.
PAL colorimetry, as defined by the ITU on REC-BT.470, and based onCIE 1931 x,y coordinates:[21]
| Standard | Year | White point | Primaries | DisplaygammaEOTF | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Red | Green | Blue | ||||||||
| xʀ | yʀ | xɢ | yɢ | xʙ | yʙ | |||||
| PAL | EBU 3213-E,ITU-R BT.470/601 (B/G) | 1970 | D65 | 0.64 | 0.33 | 0.29 | 0.60 | 0.15 | 0.06 | 2.8 |
| PAL-M | BT.470-6[22] | 1972 | C | 0.67 | 0.33 | 0.21 | 0.71 | 0.14 | 0.08 | 2.2 |
The assumeddisplay gamma is defined as 2.8.[21] ThePAL-M system uses color primary and gamma values similar to NTSC.[22] Color is encoded using theYUV color space.
Luma () is derived from red, green, and blue () gamma pre-corrected () primary signals:[18]
and are used to transmitchrominance. Each has a typical bandwidth of 1.3 MHz.
Composite PAL signaltiming[18] where.
Subcarrier frequency is 4.43361875 MHz (±5 Hz) for PAL-B/D/G/H/I/N.
The PAL colour system is usually used with a video format that has 625 lines per frame (576 visible lines, the rest being used for other information such as sync data and captioning) and arefresh rate of 50 interlaced fields per second (compatible with 25 full frames per second), such systems beingB,G,H,I, andN (seebroadcast television systems for the technical details of each format).
This ensures video interoperability. However, as some of these standards (B/G/H,I andD/K) use different sound carriers (5.5 MHz, 6.0 MHz and 6.5 MHz respectively), it may result in a video image without audio when viewing a signal broadcast over the air or cable. Some countries inEastern Europe which formerly usedSECAM with systemsD andK have switched to PAL while leaving other aspects of their video system the same, resulting in the different sound carrier. Instead, other European countries have changed completely from SECAM-D/K to PAL-B/G.[23]
The PAL-N system has a different sound carrier, and also a different colour subcarrier, and decoding on incompatible PAL systems results in a black-and-white image without sound.
The PAL-M system has a different sound carrier and a different colour subcarrier, and does not use 625 lines or 50 frames/second. This would result in no video or audio at all when viewing a European signal.
| PAL B | PAL G, H | PAL I | PAL D/K, L | PAL N | PAL M | |
|---|---|---|---|---|---|---|
| Transmission band | VHF | UHF | VHF/UHF | |||
| Fields | 50 | 60 | ||||
| Scan lines | 625 | 525 | ||||
| Active lines | 576 | 480 | ||||
| Channel bandwidth | 7 MHz | 8 MHz | 6 MHz | |||
| Video bandwidth | 5.0 MHz | 5.5 MHz | 6.0 MHz | 4.2 MHz | ||
| Vision/Sound carrier spacing | 5.5 MHz | 6.0 MHz | 6.5 MHz | 4.5 MHz | ||
| ColourSubcarrier | 4.43361875 MHz | 3.58205625 MHz | 3.575611 MHz | |||
| Assumed Receiver Gamma correction | 2.8 | 2.2 | ||||
The BBC tested their pre-war (but still broadcast until 1985)405-line monochrome system (CCIR System A) with all three colour standards including PAL, before the decision was made to abandon 405 and transmit colour on 625/System I only.
Many countries have turned off analogue transmissions, so the following does not apply anymore, except for using devices which output RF signals, such asvideo recorders.
The majority of countries using or having used PAL have television standards with 625 lines and 50 fields per second. Differences concern the audio carrier frequency and channel bandwidths. The variants are:
Systems B and G are similar. System B specifies 7 MHz channel bandwidth, while System G specifies 8 MHz channel bandwidth. Australia and China used Systems B and D respectively for VHF and UHF channels. Similarly, Systems D and K are similar except for the bands they use: System D is only used on VHF, while System K is only used on UHF. Although System I is used on both bands, it has only been used on UHF in the United Kingdom.
The PAL-L (Phase Alternating Line withCCIR System L broadcast system) standard uses the same video system as PAL-B/G/H (625 lines, 50 Hz field rate, 15.625 kHz line rate), but with a larger 6 MHz video bandwidth rather than 5.5 MHz and moving the audio subcarrier to 6.5 MHz. An 8 MHz channel spacing is used for PAL-L, to maintain compatibility with System L channel spacings.
The PAL-N standard was created inArgentina, through Resolution No. 100 ME/76,[24] which determined the creation of a study commission for a national color standard. The commission recommended using PAL underCCIR System N thatParaguay andUruguay also used. It employs the 625 line/50 field per second waveform of PAL-B/G, D/K, H, and I, but on a 6 MHz channel with a chrominance subcarrier frequency of 3.582056 MHz (917/4*H) similar to NTSC (910/4*H).[21] On the studio production level, standard PAL cameras and equipment were used, with video signals then transcoded to PAL-N for broadcast.[25] This allows 625 line, 50 frames per second video to be broadcast in a 6 MHz channel, at some cost inhorizontal resolution.
In Brazil, PAL is used in conjunction with the 525 line, 60 field/sCCIR System M, using (very nearly) the NTSC colour subcarrier frequency. Exact colour subcarrier frequency of PAL-M is 3.575611 MHz, or 227.25 times System M's horizontal scan frequency. Almost all other countries using system M use NTSC.
The PAL colour system (either baseband or with any RF system, with the normal 4.43 MHz subcarrier unlike PAL-M) can also be applied to an NTSC-like525-line picture to form what is often known as "PAL 60" (sometimes "PAL 60/525", "Quasi-PAL" or "Pseudo PAL"). PAL-M (a broadcast standard) however should not be confused with "PAL 60" (a video playback system—see below).
PAL television receivers manufactured since the 1990s can typically decode all of the PAL variants except, in some cases PAL-M and PAL-N. Many such receivers can also receive Eastern European and Middle Eastern SECAM, though rarely French-broadcast SECAM (because France used a quasi-unique positive video modulation, system L) unless they are manufactured for the French market. They will correctly display plain (non-broadcast)CVBS orS-video SECAM signals. Many can also acceptbaseband NTSC-M, such as from a VCR or game console, and RF modulated NTSC with a PAL standard audio subcarrier (i.e., from a modulator), though not usually broadcast NTSC (as its 4.5 MHz audio subcarrier is not supported). Many sets also support NTSC with a 4.43 MHz color subcarrier (see PAL 60 on the next section).
VHS tapes recorded from a PAL-N or a PAL-B/G, D/K, H, or I broadcast are indistinguishable because the downconverted subcarrier on the tape is the same. A VHS recorded off TV (or released) in Europe will play in colour on any PAL-N VCR and PAL-N TV in Argentina, Paraguay and Uruguay. Likewise, any tape recorded in Argentina, Paraguay or Uruguay off a PAL-N TV broadcast can be sent to anyone in European countries that use PAL (and Australia/New Zealand, etc.) and it will display in colour. This will also play back successfully in Russia and other SECAM countries, as the USSR mandated PAL compatibility in 1985—this has proved to be very convenient for video collectors.
People in Argentina, Paraguay and Uruguay usually own TV sets that also display NTSC-M, in addition to PAL-N.DirecTV also conveniently broadcasts in NTSC-M for North, Central, and South America. MostDVD players sold in Argentina, Paraguay and Uruguay also play PAL discs—however, this is usually output in the European variant (colour subcarrier frequency 4.433618 MHz), so people who own a TV set which only works in PAL-N (plus NTSC-M in most cases) will have to watch those PAL DVD imports in black and white (unless the TV supports RGBSCART) as the colour subcarrier frequency in the TV set is the PAL-N variation, 3.582056 MHz.
In the case that a VHS or DVD player works in PAL (and not in PAL-N) and the TV set works in PAL-N (and not in PAL), there are two options:
Some DVD players (usually lesser known brands) include an internal transcoder and the signal can be output in NTSC-M, with some video quality loss due to thestandard conversion from a 625/50 PAL DVD to the NTSC-M 525/60 output format. A few DVD players sold in Argentina, Paraguay and Uruguay also allow a signal output of NTSC-M, PAL, or PAL-N. In that case, a PAL disc (imported from Europe) can be played back on a PAL-N TV because there are no field/line conversions, quality is generally excellent.
Some special VHS video recorders are available which can allow viewers the flexibility of enjoying PAL-N recordings using a standard PAL (625/50 Hz) colour TV, or even through multi-system TV sets. Video recorders like Panasonic NV-W1E (AG-W1 for the US), AG-W2, AG-W3, NV-J700AM, Aiwa HV-M110S, HV-M1U, Samsung SV-4000W and SV-7000W feature a digital TV system conversion circuitry.
Many 1990s-onwardsvideocassette recorders sold in Europe can play back NTSC tapes. When operating in this mode most of them do not output a true (625/50) PAL signal, but rather a hybrid consisting of the original NTSC line standard (525/60), with colour converted to PAL 4.43 MHz (instead of 3.58 as with NTSC andPAL-M) — this is known as"PAL 60" (also"quasi-PAL" or"pseudo-PAL") with "60" standing for 60 Hz (for 525/30), instead of 50 Hz (for 625/25).
Some video game consoles also output a signal in this mode. TheDreamcast pioneered PAL 60 with most of its games being able to play games at full speed like NTSC and without borders.Xbox andGameCube also support PAL 60 unlike PlayStation 2.[26] ThePlayStation 2 did not actually offer a true PAL 60 mode; while many PlayStation 2 games did offer a "PAL 60" mode as an option, the console would in fact generate an NTSC signal during 60 Hz operation.
Most newer television sets can display a "PAL 60" signal correctly, but some will only do so (if at all) in black and white and/or with flickering/foldover at the bottom of the picture, or picture rolling (however, many old TV sets can display the picture properly by means of adjusting the V-Hold and V-Height knobs—assuming they have them). Some TV tuner cards or video capture cards will support this mode (although software/driver modification can be required and the manufacturers' specs may be unclear).
Some DVD players offer a choice of PAL vs NTSC output for NTSC discs.[27]
PAL usually has 576 visible lines compared with 480 lines withNTSC, meaning that PAL has a 20% higher resolution, in fact it even has a higher resolution thanEnhanced Definition standard (852x480). Most TV output for PAL and NTSC use interlaced frames meaning that even lines update on one field and odd lines update on the next field. Interlacing frames gives a smoother motion with half the frame rate.NTSC is used with aframe rate of60i or30p whereas PAL generally uses50i or25p; both use a high enoughframe rate to give the illusion of fluid motion. This is due to the fact that NTSC is generally used in countries with autility frequency of 60 Hz and PAL in countries with 50 Hz, although there are many exceptions.
Both PAL and NTSC have a higher frame rate than film which uses 24 frames per second. PAL has a closer frame rate to that of film, so most films are sped up 4% to play on PAL systems, shortening the runtime of the film and, without adjustment, slightly raising the pitch of the audio track in order to, in the case of VHS tapes and DVDs, make room for more local content made in the country (UK, Australia etc). Film conversions for NTSC instead use3:2 pull down to spread the 24 frames of film across 60 interlaced fields. This maintains the runtime of the film and preserves the original audio, but may cause worse interlacing artefacts during fast motion.
NTSC receivers have atint control to perform colour correction manually. If this is not adjusted correctly, the colours may be faulty. The PAL standard automatically cancelshue errors by phase reversal, so a tint control is unnecessary yet Saturation control can be more useful. Chrominance phase errors in the PAL system are cancelled out using a 1H delay line resulting in lower saturation, which is much less noticeable to the eye than NTSC hue errors.
However, the alternation of colour information—Hanover bars—can lead to picture grain on pictures with extreme phase errors even in PAL systems, if decoder circuits are misaligned or use the simplified decoders of early designs (typically to overcome royalty restrictions). This effect will usually be observed when the transmission path is poor, typically in built up areas or where the terrain is unfavourable. The effect is more noticeable on UHF than VHF signals as VHF signals tend to be more robust. In most cases such extreme phase shifts do not occur.
PAL and NTSC have slightly divergentcolour spaces, but the colour decoder differences here are ignored.
Outside of film and TV broadcasts, the differences between PAL and NTSC when used in the context ofvideo games were quite dramatic. For comparison, the NTSC standard is 60 fields/30 frames per second while PAL is 50 fields/25 frames per second. To avoid timing problems or unfeasible code changes, games were slowed down by approximately 16.7%. This has led to games ported over to PAL regions being historically known for their inferior speed and frame rates compared to their NTSC counterparts, especially when they are not properly optimized for PAL standards.
Full motion video rendered and encoded at 30 frames per second by the Japanese/US (NTSC) developers were often down-sampled to 25 frames per second or considered to be 50 frames per second video for PAL release—usually by means of3:2 pull-down, resulting in motionjudder. In addition, the increased resolution of PAL was often not utilised at all during conversion, creating a pseudo-letterbox effect with borders on the top and bottom of the screen, looking similar to 14:9 letterbox. This leaves the graphics with a slightly squashed look due to an incorrect aspect ratio caused by the borders.
These practices were prevalent in previous generations, especially during the8-bit and16-bit era of video games where 2D graphics were the norm at that time. The gameplay of many games with an emphasis on speed, such as the originalSonic the Hedgehog for theSega Genesis (Mega Drive), suffered in their PAL incarnations.
Starting with thesixth generation of video games, game consoles started to offer true 60 Hz modes in games ported to PAL regions. TheDreamcast was the first to offer a true "PAL 60" mode, with many games made for the system in PAL regions being closely on-par with their NTSC counterparts in terms of speed and frame rates using "PAL 60" modes. TheXbox andGameCube also featured "PAL 60" modes in games made for the region as well. The only lone exception was thePlayStation 2, where games ported over to PAL regions are oftentimes (but not always) running in 50 Hz modes. PAL region games supporting 60 Hz modes for the PlayStation 2 also requires a display with NTSC output unlessRGB orcomponent connections were used, since these allowed for colour outputs without the need for NTSC or PAL colour encoding. Otherwise, the games would display in monochrome on PAL-only displays.
The problems usually associated with PAL region video games are not necessarily encountered in Brazil with the PAL-M standard used in that region, since its video system uses an identical number of visible lines and refresh rate as NTSC but with a slightly different colour encoding frequency based on PAL, modified for use with theCCIR System M broadcast television system.
TheSECAM patents predate those of PAL by several years (1956 vs. 1962). Its creator, Henri de France, in search of a response to known NTSChue problems, came up with ideas that were to become fundamental to both European systems, namely:
SECAM applies those principles by transmitting alternately only one of the U and V components on each TV line, and getting the other from the delay line. QAM is not required, andfrequency modulation of the subcarrier is used instead for additional robustness (sequential transmission of U and V was to be reused much later in Europe's last "analog" video systems: the MAC standards).
SECAM is free of both hue and saturation errors. It is not sensitive to phase shifts between the colour burst and the chrominance signal, and for this reason was sometimes used in early attempts at colour video recording, where tape speed fluctuations could get the other systems into trouble. In the receiver, it did not require a quartz crystal (which was an expensive component at the time) and generally could do with lower accuracy delay lines and components.
SECAM transmissions are more robust over longer distances than NTSC or PAL. However, owing to their FM nature, the colour signal remains present, although at reduced amplitude, even in monochrome portions of the image, thus being subject to stronger cross colour.
One serious drawback for studio work is that the addition of two SECAM signals does not yield valid colour information, due to its use of frequency modulation. It was necessary to demodulate the FM and handle it as AM for proper mixing, before finally remodulating as FM, at the cost of some added complexity and signal degradation. In its later years, this was no longer a problem, due to the wider use of component and digital equipment.
PAL can work without a delay line (PAL-S), but this configuration, sometimes referred to as "poor man's PAL", could not match SECAM in terms of picture quality. To compete with it at the same level, it had to make use of the main ideas outlined above, and as a consequence PAL had to pay licence fees to SECAM. Over the years, this contributed significantly to the estimated 500 million francs gathered by the SECAM patents (for an initial 100 million francs invested in research).[28]
Hence, PAL could be considered as a hybrid system, with its signal structure closer to NTSC, but its decoding borrowing much from SECAM.
There were initial specifications to use colour with the French 819 line format (system E). However, "SECAM E" only ever existed in development phases. Actual deployment used the 625 line format. This made for easy interchange and conversion between PAL and SECAM in Europe. Conversion was often not even needed, as more and more receivers and VCRs became compliant with both standards, helped in this by the common decoding steps and components. When theSCART plug became standard, it could take RGB as an input, effectively bypassing all the colour coding formats' peculiarities.
When it comes to home VCRs, all video standards use what is called "colour under" format. Colour is extracted from the high frequencies of the video spectrum, and moved to the lower part of the spectrum available from tape. Luma then uses what remains of it, above the colour frequency range. This is usually done by heterodyning for PAL (as well as NTSC). But the FM nature of colour in SECAM allows for a cheaper trick: division by 4 of the subcarrier frequency (and multiplication on replay). This became the standard for SECAM VHS recording in France. Most other countries kept using the same heterodyning process as for PAL or NTSC and this is known as MESECAM recording (as it was more convenient for some Middle East countries that used both PAL and SECAM broadcasts).
Another difference in colour management is related to the proximity of successive tracks on the tape, which is a cause for chroma crosstalk in PAL. A cyclic sequence of 90° chroma phase shifts from one line to the next is used to overcome this problem. This is not needed in SECAM, as FM provides sufficient protection.
Regarding early (analogue) videodiscs, the established Laserdisc standard supported only NTSC and PAL. However, a different optical disc format, the Thomson transmissive optical disc made a brief appearance on the market. At some point, it used a modified SECAM signal (single FM subcarrier at 3.6 MHz[29]). The media's flexible and transmissive material allowed for direct access to both sides without flipping the disc, a concept that reappeared in multi-layered DVDs about fifteen years later.
Below are lists of countries and territories that used or once used the PAL system. Many of these have converted or are converting PAL toDVB-T (most countries),DVB-T2 (most countries),DTMB (China, Hong Kong and Macau) orISDB-Tb (Sri Lanka, Maldives, Botswana, Brazil, Argentina, Paraguay and Uruguay).
A legacy list of PAL users in 1998 is available onRecommendation ITU-R BT.470-6 - Conventional Television Systems, Appendix 1 to Annex 1.[30]
Afghanistan (used SECAM)[31]
Algeria
Angola[31]
Armenia
Bahrain (DVB-T introduction in assessment)[31]
Bhutan[31]
Botswana[31]
British Indian Ocean Territory[31]
Cameroon[31]
Cape Verde[31]
Christmas Island
Comoros
Cook Islands (see New Zealand)
Djibouti[31]
Equatorial Guinea[31]
Eritrea[31]
Eswatini[31]
Ethiopia[31]
Falkland Islands (UHF only)[31]
Fiji
Gambia[31]
Guinea-Bissau[31]
Iraq[31] (DVB-T introduction in assessment)
Jordan[32] (DVB-T introduction in assessment)
Kiribati[31]
Kuwait[31]
Laos (Once experimented in PAL-M)[31]
Lebanon (uses PAL for Lebanese channels)
Lesotho[31]
Liberia[31]
Libya
Malawi[31]
Maldives[31]
Mauritius
Mozambique[31]
Myanmar[31] (Unofficially, only for non-terrestrial)
Nauru[31]
Nepal[31]
Niue[31]
Norfolk Island (see Australia)
North Korea (used SECAM until 1990s)[31]
Oman (DVB-T introduction in assessment)[31]
Palestine (DVB-T introduction in assessment)
Papua New Guinea[31]
Saint Helena, Ascension and Tristan da Cunha (Two PAL-I analogue TV services operated by BFBS)
Samoa[31]
São Tomé and Príncipe
Seychelles[31]
Sierra Leone[31]
Solomon Islands
Somalia[31]
South Africa (Simulcast in DVB-T)
South Sudan
Sri Lanka[31]
Sudan[31]
Syria (along with SECAM)[31]
Timor-Leste
Tonga[31] (Simulcast in DVB-T)
Turkey
Tuvalu[31]
Uganda[31]
Vanuatu[31]
Yemen[31] (DVB-T introduction in assessment)
Zimbabwe[31]The following countries and territories no longer use PAL for terrestrial broadcasts, and are in process of converting from PAL toDVB-T/T2,DTMB orISDB-T.
| Country | Switched to | Switchover completed |
|---|---|---|
 Albania | DVB-T2 | 2019-10-011 October 2019 |
 Andorra | DVB-T | 2007-09-2525 September 2007 |
 Australia | DVB-T | 2013-12-1010 December 2013 |
 Austria | DVB-T and DVB-T2 | 2010-06-077 June 2011 |
 Azerbaijan | DVB-T | 2015-06-1717 June 2015 |
 Bangladesh | DVB-T | 2024-11-3030 November 2024 |
 Belgium | DVB-T | 2010-03-011 March 2010 |
 Bosnia and Herzegovina | DVB-T | 2024-12-3131 December 2024 |
 Brunei | DVB-T | 2015-01-011 January 2015 |
 Bulgaria | DVB-T | 2013-09-3030 September 2013 |
 Cambodia | DVB-T2 | 2015-01-011 January 2015 |
 China | DTMB | 2021-03-3131 March 2021 |
 Croatia | DVB-T2 | 2020-11-1212 November 2020[33] |
 Cyprus | DVB-T | 2011-07-011 July 2011 |
 Czech Republic | DVB-T and DVB-T2 | 2012-06-3030 June 2012 |
 Denmark | DVB-T and DVB-T2 | 2009-11-011 November 2009 |
 Egypt | DVB-T | 2024-09-3030 September 2024 |
 Estonia | DVB-T | 2010-07-011 July 2010 |
 Faroe Islands | DVB-T | 2002–12December 2002 |
 Finland | DVB-T and DVB-T2 | 2007-09-011 September 2007 |
 Georgia | DVB-T | 2015-07-011 July 2015 |
 Germany | DVB-T and DVB-T2 | 2009-06-044 June 2009 |
 Ghana | DVB-T2 | 2015-06June 2015 |
 Greece | DVB-T | 2015-02-056 February 2015 |
 Gibraltar | DVB-T | 2012-12-3131 December 2012 |
 Guernsey | DVB-T | 2010-11-1717 November 2010 |
 Hong Kong | DTMB | 2020-12-011 December 2020 |
 Hungary | DVB-T and DVB-T2 | 2013-10-3131 October 2013 |
 Iceland | DVB-T and DVB-T2 | 2015-02-022 February 2015 |
 India | DVB-T | 2015-03-3131 March 2015 |
 Indonesia | DVB-T2 | 2023-08-1212 August 2023[34] |
 Iran | DVB-T | 2014-12-1919 December 2014 |
 Ireland | DVB-T | 2012-10-2424 October 2012 |
 Isle of Man | DVB-T | 2012-10-2424 October 2012 |
 Israel | DVB-T and DVB-T2 | 2011-06-1313 June 2011 |
 Italy | DVB-T | 2012-07-044 July 2012 |
 Jersey | DVB-T | 2010-11-1717 November 2010 |
 Kenya | DVB-T | 2015-03March 2015 |
 Latvia | DVB-T | 2010-06-011 June 2010 |
 Lithuania | DVB-T | 2012-10-2929 October 2012 |
 Luxembourg | DVB-T | 2006-09-011 September 2006 |
 Macau | DTMB | 2023-06-3030 June 2023[35] |
 North Macedonia | DVB-T | 2013-05-3131 May 2013 |
 Malaysia | DVB-T2 | 2019-10-3131 October 2019 |
 Malta | DVB-T | 2011-10-3131 October 2011 |
 Monaco | DVB-T | 2011-05-2424 May 2011 |
 Moldova | DVB-T | 2024-12-3131 December 2024 |
 Mongolia | DVB-T | 2024-12-2020 December 2024 |
 Montenegro | DVB-T | 2015-06-1717 June 2015 |
 Namibia | DVB-T | 2014-09-1313 September 2014 |
 Netherlands | DVB-T | 2006-12-1414 December 2006 |
 New Zealand | DVB-T | 2013-12-011 December 2013 |
 Nigeria | DVB-T | 2024-12-1515 December 2024 |
 Norway | DVB-T | 2009-12December 2009[36] |
 Poland | DVB-T2[37] | 2013-07-2323 July 2013 |
 Portugal | DVB-T | 2012-04-2626 April 2012 |
 Qatar | DVB-T and DVB-T2 | 2012-02-1313 February 2012 |
 Romania | DVB-T2 | 2016-12-3131 December 2016 |
 Rwanda | DVB-T | 2014-03March 2014 |
 San Marino | DVB-T | 2010-12-022 December 2010 |
 Saudi Arabia | DVB-T and DVB-T2 | 2012-02-1313 February 2012 |
 Serbia | DVB-T2 | 2015-06-077 June 2015 |
 Singapore | DVB-T2 | 2019-01-022 January 2019 |
 Slovakia | DVB-T | 2012-12-3131 December 2012 |
 Slovenia | DVB-T | 2010-12-011 December 2010 |
 Spain | DVB-T and DVB-T2 | 2010-04-033 April 2010 |
 Sweden | DVB-T and DVB-T2 | 2007-10-2929 October 2007 |
 Switzerland | DVB-T | 2007-11-2626 November 2007 |
 Tanzania | DVB-T | 2014-07July 2014 |
 Thailand | DVB-T2 | 2020-03-2626 March 2020 |
 Ukraine | DVB-T and DVB-T2 | 2016-12-3131 December 2016 |
 United Arab Emirates | DVB-T and DVB-T2 | 2012-02-1313 February 2012 |
| United Kingdom | DVB-T (SD) andDVB-T2 (HD) | 2012-10-2424 October 2012 |
 Vietnam | DVB-T2 | 2020-12-2828 December 2020 |
 Zambia | DVB-T2 | 2014-12-3131 December 2014 |
In 1963, when he gave a public presentation of the Phase Alternation Line to a group of experts from the European Broadcasting Union in Hannover
In 1950s, when Telefunken commissioned Bruch to invent an automated differential phase correction for color television. That's why he was awarded.
| CAM | |
|---|---|
| CIE | |
| RGB | |
| Y′UV | |
| Other | |
| Colour systems and standards | |
For the vision capacities of organisms or machines, see  Colour vision. | |
