Phase Alternating LINE

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PAL is a procedure for Ink transfer with similar Television (as alternative to the older US-American NTSCStandard). The term PAL becomes colloquial frequently for the whole of all parameters that Television standard related.

Spreading

PAL is common before everything in Europe, however also in Australia, South America and in many African and asiatic countries is used, sees also the table in the appendix.

History

Television began originally black/white. The brightness values of the picture were only transferred, no color information. So that already existing black-and-white television sets were further applicable, the color TV systems had to be developed downward-compatibly. With a black-and-white television one could receive with slightly worsened image quality also the color radiant emittances, on a colour television set also black-and-white radiations receive.

PAL became of Walter break in Hanover/ develops and 1963 to the patent announced.

The start of the Colour television in the Federal Republic of Germany took place with the famous pressure on the red button (the one mockup was) via the vice-chancellor at that time of the Federal Republic of Germany, Willy Brandt, on the occasion of that International radio exhibition (IFA) to 25. August 1967. In this scene the color is too early connected few seconds, before the red button was pressed.

As a possible successor as intermediate step the digital television became PALplus into the 1990er years developed, however not very far spread. PALplus is downward compatible to PAL.

Comparison

PAL has the fundamental concepts of the signal transmission of the American ink transfer system NTSC taken over. PAL uses like NTSC those Quadrature amplitude modulation for the ink transfer. When the colour fluctuations typical for NTSC do not arise to improvement, however this bought with substantial additional expenditure during the circuit realization. It can however with both systems too CROSS Color and CROSS Luminance disturbances come themselves, as disturbing, colored sample (Moiré effect) or colored streaks to express can. These image interferences particularly arise with fine structures in the picture, for example smallcross-hatched shirts, which are avoided therefore by television moderators. With increased schaltungsaufwand these disturbances can be partly eliminated (Comb filter). Additionally the vertical color dissolution worsens.

The French color TV system SECAM differs not substantially from PAL/NTSC.

Television standards with PAL ink transfer

The PAL Farbsystem used usually a video format with 625 lines per picture and has a picture transmission rate of 25 pictures per second. These are transferred however only halbbildweise, D. h. it will transfer only a picture with all odd and then a picture with all straight lines, which results in a halbbildfrequenz of 50 cycles per second, the so-called Interlaced scanning. Thus one receives a flare-poor picture with small data rate of the television signal. The PAL system transfers those Television standards B, G, H, I and N. Some Eastern European States of, those their television standard of SECAM D and K to PAL, uses PAL D/K, whereby there are some exceptions, changed over in which the countries completely on PAL B/G changed over. In Brazil PAL in connection with 525 lines and 29.97 pictures per second (system becomes M) uses and a nearly identical color carrier frequency such as NTSC. All other countries, which use the transmission system "M", use NTSC for the colour television. In Argentina, Paraguay and Uruguay PAL with the 625 lines according to standard is used, however with a color carrier frequency, which is identical for NTSC nearly to. This modification of the PAL standard is called PAL n and PAL CN.

Television sets with PAL

Newer PAL TV home receivers can process and correctly show normally nearly all PAL variants (except PAL m and PAL n). Many of it can represent SECAM also error free, which is common in Eastern Europe and in the Near East. However does not function as a rule with the SECAM system, which is used in France. From it devices of French origin are excluded. Many of these newer devices get along also problem-free with NT cm signals, which of Video recorders or play consoles to be produced. However frequently problems arise, if it concerns the processing from NT sports club signals, which are radiated by fernsehstationen.

Conversion

Motion picture films are turned traditionally with 24 pictures per second, thus a run time laufzeitverkuerzung results around 4,17% on PAL devices, since PAL shows 25 pictures in the second. This faster operational sequence of the film (technical term: PAL speed UP) hardly one notices by humans, only thereby accompanying for instance the one Half-tone higher tonwiedergabe can be noticeable, if one z. B. therein occurring music pieces already of other sources ( etc..) knows ago.

Technology

PAL develops like NTSC and SECAM on the previous black-and-white television. For reasons of the compatibility the color is hidden within the black-and-white signal. Because the picture brightness (black grey white) will already transfer, it does not have to be transferred no more the complete color information. Only the color difference signals for red and blue will transfer. Color difference signal in an educated manner from the luminance signal of the appropriate color minus the anyway existing black-and-white luminance signal (R-Y, B-Y). From the three signals R-Y, B-Y and Y can be built up in the receiver the 3 color signals R, G and B again. The articles describe this YUV and Ink transfer. By those additives color blending can be built up with the three single colors if red, green and blue all other colors, limits by that Color area that Picture tubes.

PAL uses those for the transmission of the color difference signals red minus brightness (R-Y) and blue minus brightness (B-Y) just like NTSC Quadrature amplitude modulation (QAM). There with the QAM that Carrier , this is suppressed for those Demodulation but, he is needed in the receiver by a quartz oscillator is again generated, whereby these of the PAL Burst, of which per television picture line some few periods on the rear Porch of the FBASSignal one synchronizes to be transferred.

PAL possesses a procedure for the correction of wrong colors. For this the R-Y becomes signal after each line of a half-image around 180° out of phase and steps then in the signal with phase shifts of +90°, and/or -90° on (see wrong colors). The information which phase position the R-Y signal straight has, in the Burst hidden. With +90° the phase of the Bursts +135° is, with -90° according to -135°. The B-Y signal has thereby always the phase position 0°.

Representation of the FBAS signal with PAL, a character row. The PAL Burst is at point 5.

Avoidance of the color defects

The abbreviation PAL means Phase Alternating LINE, which refers to the fact that those Phase the red difference signal from line to line one inverts. In the receiver, contrary to NTSC, colour errors (in these systems correspond to the frequently arising electrical phase errors) are converted compensated by averaging of the color signal of two neighbouring lines automatically, if the color and the colour error between both lines are constant, and into a small color saturation error. Color saturation errors are noticeable to the human eye substantially less than colour errors. This is the difference and crucial advantage of the PAL procedure opposite NTSC.

One places oneself the modulation in Vector diagram forwards, then the color kind (the colour) is, in the length of the pointer the color contrast with the respective pointer in the phase (direction) (the farbsaettigung). If phase error arises, these would show up with a simple demodulation as with NTSC as colour errors. However with PAL in each second line of the carriers of the red component 179 degrees. During the demodulation this accordingly again one turns back. A possibly arisen phase error is driven and averages themselves over two following each other lines out.

1. Vector diagram: Line n, black pointers of original, blue pointers with phase error
2. Vector diagram: Line n+1, phase around 180 degrees turned
3. Vector diagram: Situation of the pointers in the line n+1 after rueckdrehung
4. Vector diagram: black: vectorial addition of the two original pointers, in blue addition of the two phase error-afflicted pointers

One assumes from line to line the color information changes only little and the color defect which can be covered likewise changes from line to line for few.

Over these conditions the colour error becomes 1. Order into a color saturation error 2. Order converted, which is negligible by the eye substantially more with difficulty to notice and therefore.

Since for the decoding of the Pa L signal the information of the current as well as the previous line are needed in each case, the detailed Pa L signal in the receiver goes through one Delay line with a running time scarcely the length of a television line (63.943?s) to storage. Then in each case an average value between that is spent straight incoming and the signal stored from the previous character row.

Unfavorable it is however that thereby the color information shifts downward, which is noticeable particularly unpleasantly with several times copied video cassettes.

Modern (digital) PAL decoders work substantially more complex:

• the previous and following lines are charged, in order to separate brightness and color signal better (2DComb filter)
• the previous and following pictures are charged, in order to separate brightness and color signal better (3DComb filter)
• no averaging from lines is used to the colour correction, but computed on basis of statistic sizes of a correction size for the color signal

Frequency of the color carrier

Choice of the NT sports club color carrier frequency

To understand the PAL Farbtraegerfrequenzwahl first the simpler choice is explained with NTSC:

The color carrier frequency was put in such a way that the disturbing caused by itMoire (particularly on the black-and-white receivers already existing) is as inconspicuous as possible and fine-structured simultaneous brightness information (fine-cross-hatched shirts in the fig. u.ae.) possible little disturbing farbbilder cause. At the same time however also the sound signal may not be disturbed.

In addition becomes:

• as high a frequency as possible selected, which must be removed however still far enough from the sound signal (4.5 MHz)
• the number of color frequency waves per line so put that after neighbouring lines the phase of the Farbtcarrier around 180° is turned (this is not the same as phase tricks of the finished color signal with PAL).

That results in then 4.5 MHz/286 * 227.5 periods = 3.57954545 MHz for the color carrier in the case of the NT sports club color modulation. About 1.3 MHz of the lower sideband and 0.4 MHz of the upper sideband will transfer of it. By the nature of the color signal with it completely determined frequencies in these sidebands arise substantially more strongly than others; in the receiver it is sufficient "to herauszufischen" these frequencies from the black-and-white picture again, in order to achieve a rather clean separation from brightness and color information to.

Choice of the PAL Farbtraegerfrequenz

The color carrier frequency was put in such a way the fact that the disturb Moire caused by it is as inconspicuous as possible and fine-structured brightness information possible little disturbing farbbilder simultaneous causes.

In addition becomes:

• as high a frequency as possible selected, is however far enough from the sound signal (5.5 MHz) distant for which.
• the number of color frequency waves per line so put that after two lines the phase of the color carrier is turned around 180°. All two lines because neighbouring lines look different by the 180° PAL Phasenschaltung, therefore contrary to NTSC the diagonal raster is developed not between neighbour lines, but between lines with a distance of 2. Altogether the phase position repeats itself thus all four lines.
• the color carrier is increased further still by 25 cycles per second, so that the breakdown raster between the half-images alternates. This is necessary, because the number of lines 625 -- differently than the NT sports club number of lines 525 -- results in a remainder of 1 in the case of the division from 8, whereby a slowly moving spurious pattern develops, which is more remarkable than a fast moving, as it develops with a remainder of 3. With PAL m, PAL with 525 lines, is not thus used this correction therefore. Also most DVD Player, and digital satellite satelliten-Receiver this correction not, there they produce in digital technique only with relatively complex - and therefore expensive - components to be produced can. It hardly looks someone DVDs on black-and-white televisions, and on color devices the disturbances are anyway less strongly visible.

That results in then 15625 cycles per second * 283.75 periods + 25 cycles per second = 4.43361875 MHz for the color carrier in the case of the PAL Farbmodulation. About 1.3 MHz of the lower sideband and 0.65 MHz of the upper sideband will transfer of it. The color carrier frequency is usually produced in the receiver by one from the television station after-to quartz oscillator. This oscillator becomes angegelichen by the Burst in frequency and phase to the oscillator with the transmitter. Thus a stable, high-constant reference frequency is available in each television set.

The used frequency becomes partly also Cousin volumeTransmission of NTSC uses and is called then NTSC-4.43. Also most newer PAL televisions can indicate such a signal problem-free, why it z.B. one uses, if one liked to regard a NTSC DVD on a PAL television. The interference suppression of the color carrier (carrier frequency is the 281,78fache of the horizontal line frequency, which no longer is half-integral) is however no longer optimal then.

Demodulation

Averaging of neighbouring lines during decoding is necessary not in principle with PAL, contrary to SECAM. One can decode each line independently also for itself. The correction of color kind errors functioned in the case of small errors still properly, averaging is taken over in the case of small colour error (like one it nowadays by cable television and other phasefirmer transmission methods frequently finds) problem-free by the human eye. The vertical dissolution in contrast to classical PAL decoding with line averaging is not reduced. During transmission of PAL via Y/C (Hosidenverbindung, S-video) also broader ribbon width is not possible, it gives restriction on 1.3899 MHz range more. Unfortunately of it hardly use is made.

References

The standard, which defines the PAL system (and also the NT sports club system), became 1998 published by that internationally Telecommunications union and has the title "Recommendation INTERNATIONAL telecommunication union r BT.470-6, Conventional television of system ". It is not publicly in the InterNet accessible, can be bought however at the International Telecommunication Union.

Appendix spreading

Countries and areas with PAL B/G or PAL D/K

Europe

, Ascension, , , , , Estland, Faroeer, Finland, , , , Ireland, Iceland, Italy, Croatia, Lettland, Liechtenstein, Litauen, Luxembourg, Macedonia, Malta, The Netherlands, Norway, Austria, Poland, Portugal (inclusively Larva Irish Republican Army and that The Azores), , Serbia and Montenegro, , , (inclusively that Kanari islands), , , Tristan there Cunha, , Turkey, Vatikan city

Asia

, Bahrain, , Brunei, , Gaza and West bank, , Indonesia, Israel, Yemen, , Qatar, Kuweit, Lebanon, Malaysia, Malediven, Nepal, Nordkorea, Oman, Pakistan, Singapur, Sri Lanka, Syrien, Thailand, Türkei, Vereinigte Arabische Emirate, Vietnam, Zypern.

Amerika

Falklandinseln

Afrika

Algerien, Angola, Äthiopien, Botswana, Eritrea, Gambia, Ghana, Guinea, Guinea-Bissau, Kamerun, Cape Verde, Kenya, Lesotho, Liberia, Malawi, Mozambique, Namibia, Nigeria, , Sansibar, Seychelles, Sierra Leone, Simbabwe, , South Africa, , Swaziland, Tanzania, Uganda.

Australia and Ozeanien

Australia, Cookinseln, New Zealand, Norfolkinsel, Osterinsel, Papua New Guinea, Salomonen, Tonga, Vanuatu, Weihnachtsinsel.

Countries and areas with PAL i

Europe

Great Britain and Northern Ireland

Asia

Hong Kong and Macau,

Countries with PAL m

America

Brazil (beside NTSC)

Asia

Laos (beside SECAM).

Countries with PAL n or PAL CN

America

, , Paraguay and Uruguay.

Digital PAL

All so far describing refers to the term PAL in the similar world, thus for example analog television and video recorder. In the digital world, approximately with digital satellite-to-receiver telecasting, newer play consoles or on a DVD, the color modulation is produced only in the playing equipment and is not stored not on the medium. Therefore "PAL" means the picture resolution of 576 visible lines for each frame within the digital range (only) with 25 frames per second - become digital usually (z.B. up DVD or with most digital television stations) 720 × 576 Pixel per picture stored, more rarely 480 × 576 (up SVCD) or 352 × 288 (up Video CD) and/or. 544 × 576 or 704 × 576 (by DVB). Between PAL and SECAM no more difference insists on a digital medium - a PAL DVD Player produces from a PAL DVD a PAL video signal, a SECAM DVD Player from the same PAL DVD a SECAM video signal. And also only when control by FBAS/Composite video/RCA or S-video/YC/HosidenConnection. To RGB/SCART or YUVConnection or via digital interfaces (DVI, HDMI) no more color standard arises. Only NTSC something other meaning has, i.e. the dissolution of 480 lines for each frame with either 29.97 or (for features) 23.976 frames per second on digital media. Nearly all PAL DVD Player can however also from this PAL-60 PAL similar signal mentioned produce, with which nearly all newer PAL television sets get along problem-free.

Additionally to forming out of the digital PAL specified above there is also still another further form. With this form the similar signal with the quadruple becomes Color subcarrier frequency scanned. Those Scanning happens synchronously at Burst. It is moderately simply, through Addition and Subtraction more intimate Scanning values those Color difference signals to receive. This procedure is used particularly internally in videofinished devices. Digital television sets work here frequently with 7 or 8-bit scanning values, better devices use up to 10 bits. Early digital Video recorder (for example d2) likewise this procedure used.

See also

• Frequencies of the television channels

Web on the left of

• Color coding procedure of nearly all states and their television standards
• Representation of the different speeds of PAL -, NTSC and motion picture films
• Video dissolutions - why is the PAL dissolution variable and as came it to the non-square pixels? (reference: In this horizontal lines ziterten left from the technical literature refer only to a square screen window and not to the whole picture. Therefore the author u could.A. do not reconstruct the data by computations of the ranges. The horizontal dissolution of PAL similar is normally indicated in MHz.)