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[[Motion picture]]s are typically shot on film at 24 frames per second. When [[telecine|telecined]] and played back at PAL's standard of 25 frames per second, films run 4.2% faster. [http://www.michaeldvd.com.au/Articles/PALSpeedUp/PALSpeedUp.asp] Unlike NTSC's telecine system, which uses [[Telecine#3:2_pulldown_.28technically.2C_2:3_pulldown.29|3:2 pulldown]] to convert the 24 frames per second to the NTSC frame rate, PAL results in the telecined video running 4.2% shorter than the original film as well as the equivalent NTSC telecined video. Depending on the sound system in use, it also increases the pitch of the soundtrack by 70.67 [[cent (music)|cent]] — ⅔ of a [[semitone]], which only the minority of people with [[absolute pitch]] will notice.
[[Motion picture]]s are typically shot on film at 24 frames per second. When [[telecine|telecined]] and played back at PAL's standard of 25 frames per second, films run 4.2% faster. [http://www.michaeldvd.com.au/Articles/PALSpeedUp/PALSpeedUp.asp] Unlike NTSC's telecine system, which uses [[Telecine#3:2_pulldown_.28technically.2C_2:3_pulldown.29|3:2 pulldown]] to convert the 24 frames per second to the NTSC frame rate, PAL results in the telecined video running 4.2% shorter than the original film as well as the equivalent NTSC telecined video. Depending on the sound system in use, it also increases the pitch of the soundtrack by 70.67 [[cent (music)|cent]] — ⅔ of a [[semitone]], which only the minority of people with [[absolute pitch]] will notice.


However, some movie enthusiasts prefer PAL speed-up over NTSC's 3:2 pulldown, because the latter results in [[Telecine#Telecine judder|telecine judder]], a visual distortion not present in PAL sped-up video. <ref name="Enthusiasts">
However, some movie enthusiasts prefer PAL speed-up over NTSC's 3:2 pulldown, because the latter results in [[Telecine#Telecine judder|telecine judder]], a visual distortion not present in PAL speed-up video. <ref name="Enthusiasts">
[http://www.dvdlard.co.uk/Content.aspx?ContentID=109 DVDLard] states ''"the majority of authorities on the subject favour PAL over NTSC for DVD playback quality"''. Also DVD reviewers often make mention of this cause. For example, in his [http://www.michaeldvd.com.au/Articles/PALvsNTSC/PALvsNTSC.asp PAL vs. NTSC article], the founder of [http://www.michaeldvd.com.au MichaelDVD] says ''"Personally, I find {3:2 pulldown} all but intolerable and find it very hard to watch a movie on an NTSC DVD because of it."'' In the [http://www.michaeldvd.com.au/Reviews/Reviews.asp?ID=3999 review of Frequency], one of his reviewers mentions ''"because of the 3:2 pull-down artefacts that are associated with the NTSC format (...) I prefer PAL pretty much any day of the week"''. </ref> This is not an issue on modern [[upconverting]] DVD players and [[personal computer|PCs]], as they play back 23.97fps-encoded video at its true frame rate, without 3:2 pulldown.
[http://www.dvdlard.co.uk/Content.aspx?ContentID=109 DVDLard] states ''"the majority of authorities on the subject favour PAL over NTSC for DVD playback quality"''. Also DVD reviewers often make mention of this cause. For example, in his [http://www.michaeldvd.com.au/Articles/PALvsNTSC/PALvsNTSC.asp PAL vs. NTSC article], the founder of [http://www.michaeldvd.com.au MichaelDVD] says ''"Personally, I find {3:2 pulldown} all but intolerable and find it very hard to watch a movie on an NTSC DVD because of it."'' In the [http://www.michaeldvd.com.au/Reviews/Reviews.asp?ID=3999 review of Frequency], one of his reviewers mentions ''"because of the 3:2 pull-down artefacts that are associated with the NTSC format (...) I prefer PAL pretty much any day of the week"''. </ref> This is not an issue on modern [[upconverting]] DVD players and [[personal computer|PCs]], as they play back 23.97fps-encoded video at its true frame rate, without 3:2 pulldown.


Revision as of 07:46, 29 March 2007

For other uses, see PAL (disambiguation).
Television encoding systems by nation

PAL, short for Phase Alternating Line, is a colour encoding system used in broadcast television systems in large parts of the world. Other common analogue television systems are SECAM and NTSC.

History of the PAL standard

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 and Germany in 1967. [1]

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 nowadays 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, principally European) television system, and to differentiate from a 525-line/60 Hz (480i, principally North American/Central American/Japanese) "NTSC" system. Accordingly, DVDs are labelled as either "PAL" or "NTSC" (referring informally to the line count and frame rate) even though technically neither of them have encoded PAL or NTSC composite colour.

PD: Paraguay use the PAL-N system over the national broadcast TV system.

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 (CVBS). The frequency of this subcarrier is typically 4433618.75 Hz (approximately 4.43 MHz) for PAL, compared to approximately 3.58 MHz for NTSC. The SECAM system, on the other hand, uses a frequency modulation scheme on its colour subcarrier. 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 canceling; however this resulted in a comb-like 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.

PAL vs NTSC

Because the PAL format has greater resolution than NTSC, it is generally accepted as being of higher quality, especially for DVD movies.[2] NTSC receivers have a tint control to perform that correction manually. Some engineers jokingly expand NTSC to "Never Twice the Same Color" or "Not The Same Color" while referring to PAL as "Perfect At Last", "Peace At Last", or "Pay for Additional Luxury".

However, the alternation of colour information—Hanover bars—can lead to picture grain on pictures with extreme phase errors even in PAL systems, causing some engineers to alternatively expand PAL to "Picture Always Lousy" or "Pretty Awful Looking". Another expansion is "Pay Another Licence" in reference to the British television licence fee which is higher for colour sets.

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 PLL circuit.
  • 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 spaces, but the colour decoder differences here are ignored.
  • 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.

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 them can also receive Eastern European and Middle Eastern SECAM, though usually not French SECAM, unless they are made for the French market. Many of them can also accept baseband NTSC-M, such as from a VCR or game console, though not usually broadcast NTSC.

Many newer Video Cassette recoders (and DVD players) sold in Europe can play back NTSC tapes/discs. When operating in this mode most of them dont output a true (625/25) PAL signal but rather a hybrid of PAL and NTSC known as "PAL 60" (or "pseudo PAL"). 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 analog-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).

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.

  • 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 above)

See PAL-M (television)

PAL-Nc

In Argentina, the PAL-Nc (combination N) variant is used. The same 625-line system as PAL-G,D,G,H, and I is used with the same 4.43 MHz colorburst frequency. [The difference shows up on baseband signals. Need some clarification of the difference.]

PAL-N

In Paraguay and Uruguay, PAL is used with the standard 625 line system, but again with (very nearly) the NTSC colour subcarrier frequency (3.58 MHz); this variant is called and PAL-N.

  • PAL-N should not be viewed as wildly incompatible versions of the PAL system, only the choice of colour subcarrier is different.
  • Most PAL recorders, DVD players etc support baseband (colour subcarrier free) connections -- so PAL-N systems are not as problematic as they used to be.

PAL-L

There is one more least frequently used variety of PAL called PAL-L. In this peculiar TV-System, Pal is used with standard 625 scan lines. PAL-L keeps the ability of PAL to furnish images with the correct hue, and in ensuring that consistancy in saturation of colour as well is maintained.It only uses L-sound system with PAL type of scan lines.Its a slight deviation from normal PAL-BG with the knowledge that B,G,L use the same number of scan lines and Frame rate as 625 and 25 respectively. Its differs in channel bandwidth and visual bandwidth as L-system has values 8 and 6 respectively for channel bandwidth and visual bandwidth.(B,G has values ch.bandwidth = 7, visual bandwidth = 5). The sound offset in B and G is +5.5 whereas in L its +6.5. In layman's language, PAL-L is PAL-BG with positive and AM sound modulation.(sound is amplitude modulated and has positive modulation) This system is used in some hotel's internal transmission and in public transports.One example of a Tv with PAL-L support is Thomson 24WK25. This is defined by Sandipan Bhattacharjee,India.

All PAL systems interoperable except PAL-M (525/50)

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 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 systems 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. [citation needed]

On RF (i.e via 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 FM sound carriers on PAL B/G. (Stereo FM Radio uses a mono signal with a DSBSC L-R audio centered on 38 kHz with a 19 kHz pilot to aid decoding. Hence the German Zweiton and Nicam both give better performance than FM Radio).

Baseband interoperability (analog)

When PAL video is transmitted via baseband (via consumer device cables, not RF), most of the differences between the "one-letter" systems are no longer significant, other than vertical resolution and frame rate.

In this context, unqualified PAL invariably means

  • 576 lines
  • 25 frames per second
  • interlaced video
  • with PAL colour (4.43 MHz or 3.58 MHz (PAL-M, PAL-N & PAL-NC))
  • FM audio (mono) as only French SECAM uses AM modulation for audio
  • mono or stereo audio if sent via connector cables between devices

Baseband interoperability (digital)

In digital video applications, such as DVDs and digital broadcasting, colour encoding is no longer significant; in that context, PAL means only

  • 576 lines
  • 25 frames/50 fields {second}
  • interlaced video
  • PCM audio (baseband)

There is no longer any difference (in the digital domain) between PAL and SECAM. Digital video uses its own separate colour space, so even the minor colour space differences between PAL and SECAM become moot in the digital domain.

Use with Progressive Sources

When PAL is used to transmit content which was originally composed of 25 progressive full frames per second, the odd field of the frame is transmitted first. This is opposite to NTSC. Systems which recover progressive frames, or transcode video should ensure that this 'Field Order' is obeyed, otherwise the recovered frame will consist of a field from one frame and a field from an adjacent frame, resulting in 'comb' interlacing artifacts.

PAL speed-up

Motion pictures are typically shot on film at 24 frames per second. When telecined and played back at PAL's standard of 25 frames per second, films run 4.2% faster. [1] Unlike NTSC's telecine system, which uses 3:2 pulldown to convert the 24 frames per second to the NTSC frame rate, PAL results in the telecined video running 4.2% shorter than the original film as well as the equivalent NTSC telecined video. Depending on the sound system in use, it also increases the pitch of the soundtrack by 70.67 cent — ⅔ of a semitone, which only the minority of people with absolute pitch will notice.

However, some movie enthusiasts prefer PAL speed-up over NTSC's 3:2 pulldown, because the latter results in telecine judder, a visual distortion not present in PAL speed-up video. [3] This is not an issue on modern upconverting DVD players and PCs, as they play back 23.97fps-encoded video at its true frame rate, without 3:2 pulldown.

Software which corrects the speed-up is available for those viewing PAL DVD films on their computers, WinDVD's "PAL TruSpeed" being the most ubiquitous. This method results in a slight decrease in audio quality.

Countries and territories that use PAL B, G, D, H or I

Europe

Asia

Africa

Oceania

Note about Australia & NZ with respect to stereo audio:

  • Australia & NZ have identically allocated UHF TV bands.
  • NZ's use of NICAM means that imported Australian TV sets only work in mono.
  • NZ and Australia have incompatible VHF TV bands, namely the primary carrier frequencies are different. In some cases the offsets are minor, but in others very significant.
  • DVB-T (using UHF band) may eliminate the incompatibility issues between Australia and NZ's TV frequency allocations.

Countries and territories that use PAL-I

Europe

Asia

The Americas

Africa (all both VHF and UHF)

Countries and territories that use PAL-M

Americas

Asia

  •  Laos (SECAM & PAL-M)

Countries that use PAL-N or PAL-NC

Americas

References

  1. ^ The standard that defines the PAL system was published by the International Telecommunications Union in 1998 and has the title Recommendation ITU-R BT.470-6, Conventional Television Systems
  2. ^ PAL vs NTSC
  3. ^ DVDLard states "the majority of authorities on the subject favour PAL over NTSC for DVD playback quality". Also DVD reviewers often make mention of this cause. For example, in his PAL vs. NTSC article, the founder of MichaelDVD says "Personally, I find {3:2 pulldown} all but intolerable and find it very hard to watch a movie on an NTSC DVD because of it." In the review of Frequency, one of his reviewers mentions "because of the 3:2 pull-down artefacts that are associated with the NTSC format (...) I prefer PAL pretty much any day of the week".

Digital Broadcasting Australia -http://www.dba.org.au/index.asp?sectionID=89

See also

Retrieved from "https://en.wikipedia.org/w/index.php?title=PAL&oldid=118727797"