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Television encoding systems by nation.
Countries using the PAL system are shown in blue.
NTSC is green and SECAM is orange.
(20th century)


PAL, short for Phase Alternating Line, is an analogue television encoding system used in broadcast television systems in large parts of the world. Other common analogue television systems are SECAM and NTSC. This page primarily discusses the colour encoding system. See the articles on broadcast television systems and analogue television for additional discussion of frame rates, image resolution and audio modulation. For discussion of the 625-line / 25 frame per second television standard, see 576i.

History of the PAL standard

In the 1950s, when the Western European countries were planning to establish colour television, they were faced with the problem that the NTSC standard demonstrated several weaknesses, including colour tone shifting under poor transmission conditions, earning it a comically maligned backronym "Never Twice the Same Color". For these reasons the development of the SECAM and PAL standards began. 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 by Walter Bruch at Telefunken in Germany. The format was first unveiled in 1963, with the first broadcasts beginning in the United Kingdom in 1964 and Germany in 1967, though the one BBC channel initially using the broadcast standard only began to broadcast in colour from 1967.

Telefunken was later bought by the French electronics manufacturer Thomson. Thomson also bought the Compagnie Générale de Télévision where Henri de France developed SECAM, historically the first European colour television standard. Thomson also co-owns the RCA brand for consumer electronics products, which created the NTSC colour TV standard before Thomson became involved.

The term PAL is often used informally to refer to a 625-line/50 Hz (576i), television system, and to differentiate from a 525-line/60 Hz (480i) NTSC system. Accordingly, DVDs are labelled as either PAL or NTSC (referring informally to the line count and frame rate) even though technically the discs do not have either PAL or NTSC composite colour. The line count and frame rate are defined as EIA 525/60 or CCIR 625/50. PAL and NTSC are only the method of the colour transmission used.

Technical details

The basics of PAL and the NTSC system are very similar; a quadrature amplitude modulated subcarrier carrying the chrominance information is added to the luminance video signal to form a composite video baseband signal. The frequency of this subcarrier is 4.43361875 MHz for PAL, compared to 3.579545 MHz for NTSC. 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. 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 imperfections of the human eye to do that cancelling; however this resulted in a comblike effect on larger phase errors. Thus, most receivers now use a chrominance 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 the picture tube. The effect is that phase errors result in saturation 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 luminance signal.

spectrum of a system G (bands IV and V) television channel with PAL colour).
Oscillogram of composite PAL signal - several lines.
Oscillogram of composite PAL signal - two lines.


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 is 15625 Hz, the colour carrier frequency calculates as follows: 4.43361875 MHz = 283.75 * 15625 Hz + 25 Hz.

The original colour carrier is required by the colour decoder to recreate the colour difference signals. Since the carrier is not transmitted with the video information it has to be generated locally in the receiver. In order that the phase of this locally generated signal can match the transmitted information, a 10 cycle burst of colour subcarrier is added to the video signal shortly after the line sync pulse but before the picture information (the back porch). This colour burst is not actually in phase with the original colour subcarrier but leads it by 25 degrees on the odd lines and lags it by 25 degrees on the even lines. This 'swinging burst' (as it is known) enables the colour decoder circuitry to distinguish the phase of the B-Y vector which reverses every line.

  • CVBS is an initialism, but it does not stand for "composite video baseband signal", CVBS actually stands for hroma, ideo, (B)lanking and ync; which are the four basic components of a composite video signal. That's why it's called "composite". The same signal is called FBAS in German which stands for Farbe, Bild, Austastung and Synchron.


PAL vs. NTSC

NTSC receivers have a tint control to perform colour correction manually. If this is not adjusted correctly, the colours may be faulty. The PAL standard automatically removes hue errors by utilising phase alternation of the colour signal (see technical details), so a tint control is unnecessary. 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). In most cases such extreme phase shifts do not occur. 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.

A PAL decoder can be seen as a pair of NTSC decoders:
  • PAL can be decoded with two NTSC decoders.
  • By switching between the two NTSC decoders every other line it is possible to decode PAL without a phase delay line or two phase-locked loop circuits.
  • This works because one decoder receives a colour subcarrier with negated phase in relation to the other decoder. It then negates the phase of that subcarrier when decoding. This leads to smaller phase errors being cancelled out. However, a delay line PAL decoder gives superior performance. Some Japanese TVs originally used the dual NTSC method to avoid paying royalty to Telefunken.
  • PAL and NTSC have slightly divergent colour space, but the colour decoder differences here are ignored.
* PAL supports SMPTE 498.3 while NTSC is compliant with EBU Recommendation 14.
  • The issue of frame rates and colour subcarriers is ignored in this technical explanation. These technical details play no direct role (except as subsystems and physical parameters) to the decoding of the signal.


PAL vs. SECAM

SECAM is an earlier attempt at compatible colour television which also tries to resolve the NTSC hue problem. It does so by applying a different method to colour transmission, namely alternate transmission of the U and V vectors and frequency modulation, while PAL attempts to improve on the NTSC method.

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.Like PAL, a SECAM receiver needs a delay line.

PAL Signal details

For PAL-B/G the signal has these characteristics.

Parameter Value
Clock frequency
Bandwidth
Horizontal sync polarity Negative
Total time for each line
Front porch (A)
Sync pulse length (B)
Back porch (C)
Active video (D)


(Total horizontal sync time 12.05 µs)

It should be noted that after 0.9 µs a colourburst of cycles is sent. Most rise/fall times are in range. Amplitude is 100% for white level (white colour on a monochrome receiver), 30% for black, and 0% for sync.The CVBS electrical amplitude is Vpp and impedance of 75 Ω.



The vertical timings are:
Parameter Value
Vertical lines 313 (625 total)
Vertical lines visible 288 (576 total)
Vertical sync polarity Negative (burst)
Vertical frequency
Sync pulse length (F) (burst)
Active video (H) 18.4 ms


(Total vertical sync time 1.6 ms)

As PAL is interlaced, every two lines are summed to make a complete picture frame.

Luminance, Y, is derived from red, green, and blue (R'G'B') signals:
  • Y= 0.299R' + 0.587G' + 0.114B'


U and V are used to transmit chrominance. Each has a typical bandwidth of 1.3 MHz.
  • U = 0.492(B'-Y)
  • V = 0.877(R'-Y)


Composite PAL signal = Y + U \sin (\omega t) + V \cos (\omega t) +timing where \omega = 2\pi F_{SC}.

Subcarrier frequency F_{SC} is 4.43361875 MHz (±5 Hz) for PAL-B/D/G/H/I/N.

An interesting comparison can be made with the VGA signal, the most notable differences being the double horizontal sweep time and interlace mode.

PAL broadcast systems

This table illustrates the differences:
PAL B PAL G, H PAL I PAL M PAL D PAL N PAL Nc
Transmission Band VHF UHF UHF/VHF UHF/VHF VHF UHF/VHF UHF/VHF
Lines/Fields 625/50 625/50 625/50 525/60 625/50 625/50 625/50
Video Bandwidth 5.0 MHz 5.0 MHz 5.5 MHz 4.2 MHz 6.0 MHz 5.0 MHz 4.2 MHz
Sound Carrier 5.5 MHz 5.5 MHz 6.0 MHz 4.5 MHz 6.5 MHz 5.5 MHz 4.5 MHz
Channel Bandwidth 7 MHz 8 MHz 8 MHz 6 MHz 8 MHz 6 MHz 6 MHz
Active lines 576 576 582* 480 576 576 576


  • The UK's adoption of 582 active lines has no significant impact on either non system I receivers or non system I source material as the extra lines are not within the normal display area and don't contain anything in the other standards anyway. All Digital TV broadcasts and digital recordings (e.g. DVDs) conform to the 576 active line standard.


PAL B/G/D/K/I

The majority of countries using PAL have television standards with 625 lines and 25 frames per second, differences concern the audio carrier frequency and channel bandwidths. Standards B/G are used in most of Western Europe, standard I in the UK, Ireland, Hong Kong and Macau, standards D/K in most of Central and Eastern Europe and Standard D in mainland China. Most analogue CCTV cameras are Standard D.

7-MHz channels are used in VHF (B, D) and 8-MHz channels in UHF (G, K, I), although Australia used 7-MHz channels in UHF and Ireland uses 8-MHz channels in VHF.

PAL-M standard (Brazil)

In Brazil, PAL is used in conjunction with the 525 line, 29.97 frame/s system M, using (very nearly) the NTSC colour subcarrier frequency. Exact colour subcarrier frequency of PAL-M is 3.575611 MHz
  • 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-like 525-line (480i) picture to form what is often known as "PAL-60" (sometimes "PAL-60/525" or "Pseudo PAL"). PAL-M (a broadcast standard) however should not be confused with "PAL-60" (a video playback system - see below).

PAL-Nc

In Argentina, the PAL-Nc (combination N) variant is used. It employs the 625 line/50 field per second waveform of PAL-B/G, D/K, H, I, but with a chrominance subcarrier frequency of 3.582 MHz. VHS tapes recorded from a PAL-Nc or a PAL-B/G, D/K, H, I broadcast are indistinguishable because the downconverted subcarrier on the tape is the same.

PAL-N

In Paraguay and Uruguay, PAL is used with the standard 625 line/50 fields per second system, but again with (very nearly) the NTSC subcarrier frequency.

  • PAL-N should not be viewed as a wildly incompatible version of the PAL system, only the choice of colour subcarrier is different.
  • 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 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 Uruguay, Argentina and Paraguay usually own TV sets that also display NTSC-M, in addition to PAL-N.Direct TV also conveniently broadcasts in NTSC-M for North, Central and South America. Most DVD players sold in Argentina, Uruguay and Paraguay 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 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:

  • images can be seen in black and white, or
  • an inexpensive transcoder (PAL -> PAL-N) can be purchased in order to see the colours


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 the system's conversion from a 625/50 PAL DVD disc to the NTSC-M 525/60 output format. A few DVD players sold in Argentina 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 is no fields/lines conversion, quality is generally excellent.

Extended features of the PAL specification, such as Teletext, are implemented quite differently in PAL-N. PAL-N supports a modified 608 closed captioning format that is designed to ease compatibility with NTSC originated content carried on line 18, and a modified teletext format that can occupy several lines.

PAL L

The PAL L (Phase Alternating Line with L-sound system) standard uses the System "PAL" video standard, which is the same as PAL-B/G/H (625 lines, 50 Hz field rate, 15.625 kHz line rate) except that it uses 6 MHz video bandwidth rather than 5.5 MHz - this has the result of lifting the audio subcarrier to 6.5 MHz. When System L is used with SECAM, the audio carrier is amplitude modulated, but when used with PAL the more standard FM sound system is utilised. The sound offset in B and G is +5.5 MHz, whereas in L the offset is +6.5 MHz - in layman's terms, PAL-L is PAL-BG with positive and AM sound modulation. An 8 MHz channel spacing is used with PAL-L.

PAL-L is used on some hotel internal distribution systems, as well as other public display and plant television systems. It is not used by any national TV networks. One example of a TV with PAL-L support is Thomson 24WK25.

System A

The BBC tested their pre-war 405 line monochrome system with all three colour standards including PAL, before the decision was made to abandon 405 and transmit colour on 625/System I only.

All PAL systems interoperable except PAL-M (525/60)

The PAL colour system is usually used with a video format that has 625 lines per frame (576 visible lines, 582 for System I, the rest being used for other information such as sync data and captioning) and a refresh rate of 50 interlaced fields per second (i.e. 25 full frames per second), such as systems B, G, H, I, and N (see broadcast television system for the technical details of each format).
  • Some countries in Eastern Europe which formerly used SECAM with systems D and K have switched to PAL while leaving other aspects of their video system the same.
  • However, some European countries have changed completely from SECAM-D/K to PAL-B/G.


On RF (i.e. through a modulator or TV aerial) the difference between I, D/H and B/G is audio. These use different audio subcarriers, so with mismatch on Modulator Settings or an imported TV there will be perfectly normal Colour Video, but possibly no audio. Some TVs and VHS tuners have multiple filters in parallel or switched for the 6 MHz, 5.5 MHz, 6.5 MHz or 4.5 MHz sound carriers. NICAM is an additional 6.5 MHz offset carrier carrying stereo digitally, on 6.0 MHz PAL-I systems. Germany particularly uses two separate analogue FM sound carriers on PAL-B/G. (Stereo FM Radio uses a mono signal with a DSBSC L-R audio centred on 38 kHz with a 19 kHz pilot to aid decoding. Hence the German analogue Zweikanalton and the digital NICAM both give better performance than FM Radio).

Multisystem PAL support and "PAL 60"

Recently manufactured PAL television receivers can typically decode all of these systems except, in some cases, PAL-M and PAL-N. Many of receivers can also receive Eastern European and Middle Eastern SECAM, though rarely French-broadcast SECAM (because France uses the unique positive video modulation) unless they are manufactured for the French market. They will correctly display plain CVBS or S-video SECAM signals. Many can also accept baseband 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 subcarrier.

Many newer VCR players sold in Europe can play back NTSC tapes/discs. When operating in this mode most of them do not output a true (625/25) PAL signal but rather a hybrid of PAL and NTSC known as "PAL 60" (or "pseudo PAL") with "60" standing for 60 Hz, instead of 50 Hz. Some video game consoles also output a signal in this mode. Most newer television sets can display such a 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 (it can be noted, however, that many analogue-era TV sets can receive the picture by means of adjusting the V-Hold and V-Height knobs — assuming they have them). Very few TV tuner cards or video capture cards will support this mode (a small number can, although software/driver modification is usually required and the manufacturers' specs are usually unclear). A "PAL 60" signal is similar to an NTSC (525/30) signal but with a PAL chrominance subcarrier at 4.43 MHz (instead of 3.58) and with the PAL-specific phase alternation of the red colour difference signal between the lines.

The majority, if not all, European DVD players output a true NTSC-M signal when playing NTSC discs which all modern European TV sets can resolve.

Countries and territories using PAL

Over 120 countries and territories use or once used the terrestrial PAL system. Many of these are currently converting terrestrial PAL to DVB-T (PAL still often used by cable TV or in conjunction with a digital standard, such as DVB-C).

PAL B, G, D, K or I

  • DVB-T introduction started in 2004
  • Ascension Islandmarker PAL broadcast to be abandoned by 2012, simulcast in DVB-T
  • DVB-T introduction started in 2001 (PAL to be abandoned for DVB-T by 2012)
  • DVB-T introduction started in 2006
  • In Flanders, analogue terrestrial broadcasts have ceased on 3 November 2008 and DVB-T broadcasts started in 2002. Walloniamarker will turn off the analogue transmitters in 2011.
  • (migrated from SECAM 1994–1996) (set to migrate to DVB-T in 2012, although such broadcasts are currently only available in Sofiamarker)
  • (PAL-D, digital broadcast using DMB-T/H)
  • (see Australia)
  • (see New Zealand)
  • (PAL to be abandoned for DVB-T by 1 January 2011)
  • (migrated from SECAM 1992–1994) (DVB-T introduction started in 2006, PAL to be abandoned for DVB-T by 2012)
  • (Timor-Leste)
  • (migrated from SECAM 1992–1999; PAL to be abandoned for DVB-T by 1 July 2010)
  • (UHF only)
  • (East Germanymarker used SECAM, after reunification migrated to PAL in early 1990s; PAL broadcast abandoned at the end of 2008; DVB-T introduction started in 2003)
  • (migrated from SECAM in ca. 1992, DVB-T introduction started in 2006)
  • (PAL-I, DMB-T/H introduced since 31 December 2007, PAL-I broadcast planned to be abandoned in 2012)
  • (migrated from SECAM 1995–1996; PAL broadcast to be abandoned by 31 December 2011; is converting to DVB-T)
  • (PAL broadcast to be abandoned by 2018; simulcast in DVB-T since 2008)
  • (VHF and UHF)
  • (PAL broadcast to be abandoned by 2012; is converting to DVB-T)
  • (migrated from SECAM 1997–1999, 2000 PAL-D)
  • (migrated from SECAM 1997–1999)


  • (PAL-I)
  • (PAL broadcast to be abandoned by 2012; DVB-T introduction started in 2005)
  • (Preliminary DVB-T Trials ended, further trials planned. Set top box and Digital TV not yet available on sale, but USB DVB-T receivers for viewing on a computer are widely available now. Plans to abandon PAL broadcast by 2015)
  • (Broadcasting now in DVB-T)
  • (PAL broadcast to be abandoned by 2012–2017, simulcast in DVB-S (since 2007) & DVB-T (gradually rolled out since mid-2008 starting with major centres))
  • (see Australia)
  • PAL broadcast to be abandoned by 2008–2009, simulcast in DVB-T
  • (Gazamarker & West Bankmarker)
  • (migrated from SECAM 1993–1995; PAL broadcast to be abandoned by 2012; is converting to DVB-T)
  • , including and (PAL broadcast to be fully abandoned by 2011, DVB-T simulcast since 2007)
  • (PAL broadcast to be abandoned by 2010–2011; is converting to DVB-T since early 2007)
  • , Samoa is converting to NTSC and probably ATSC
  • (which also uses SECAM)
  • (DVB-T introduction started in 2005, PAL broadcast to be abandoned by 2015)
  • (which also uses DVB-T for HDTV broadcasts)
  • (migrated from SECAM 1993–1996; PAL to be abandoned by 2012, is converting to DVB-T)
  • (PAL broadcast to be abandoned by the end of 2010; is converting to DVB-T)
  • PAL broadcast to be abandoned by 2011; is converting to DVB-T
  • (including ) is converting to simulcast in DVB-T since 31 December 2008. PAL broadcast to be fully abandoned by 04/03/2010.
  • , Tonga is converting to NTSC and probably ATSC
  • (along with SECAM)
  • (UHF only), PAL broadcast to be abandoned by 2012, simulcast in DVB-T


PAL-M

  • (simulcast with digital format in SBTVD-T, an update to ISDB-T, started in December 2007. PAL broadcast continues until 2016)
  • (also uses SECAM)


PAL-N and PAL-Nc

  • (ISDB-T with Brazilian mods chosen for Digital TV)
  • (will use DVB but no date decided yet)


Countries and territories that once used PAL

Country Switched to Switchover completed
DVB-T 25 September 200725 September 2007
DVB-T 1 November 20091 November 2009
DVB-T 1 September 20071 September 2007
DVB-T 1 September 20061 September 2006
DVB-T 14 December 200614 December 2006
DVB-T 15 October 200715 October 2007
DVB-T 26 November 200726 November 2007


See also



References

External links




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