According to abbreviationfinder, PAL is the acronym for Phase Alternating Line. It is the name given to the coding system used in the transmission of analog color television signals in most of the world. It is used in most African, Asian and European countries, as well as Australia and some American countries.

History

The PAL system emerged in 1963, from the hands of Dr. Walter Bruch in the Telefunken laboratories in his attempt to improve the quality and reduce the defects in the color tones that the NTSC system presented. However, the fundamental concepts of signal transmission have been adopted from the NTSC system.

Technical details

The name phase alternating line (in Spanish line alternated in phase) refers to the way in which the chrominance information (color) of the video signal is transmitted, being inverted in phase in each line, allowing automatic correction of possible errors. in phase by canceling each other. In radio frequency data transmission, phase errors are common and are due to signal delays in its arrival or processing. Phase errors in analog video transmission cause an error in color tone, negatively affecting image quality.

Taking advantage of the fact that the color content of one line and the next is usually similar, the receiver automatically compensates for color tone errors by taking the average value of one line and the next for the display on the screen, given that the possible error of existing phase between the two will be opposite. In this way, instead of seeing this error as a shift in tone, as would occur in NTSC, it is seen as a slight defect in color saturation, which is much less noticeable to the human eye. This is the great advantage of the PAL system over the NTSC system.

Lines where the phase is reversed from how they would be transmitted in NTSC are often called PAL lines, and those that would match are called NTSC lines.

The operation of the PAL system implies that it is constructively more complicated to realize than the NTSC system. This is because, although early PAL receivers took advantage of the imperfections of the human eye to cancel out phase errors, without the electronic correction explained above (averaging), this resulted in a highly visible comb effect if the error exceeded 5º. The solution was to introduce a delay line in the luminance signal processing of approximately 64 µs that serves to store the chrominance information.of each received line. The average chrominance of one line and the next is what is displayed on the screen. Devices that were capable of producing this delay were relatively expensive at the time PAL was introduced, but receivers are now manufactured at very low cost.

This solution reduces vertical color resolution compared to NTSC, but since the human retina is much less sensitive to color information than it is to luminance or brightness, this effect is not very visible. NTSC televisions incorporate a color tint corrector (in English, tint control’ ) to perform this correction manually.

The PAL system is more consistent than the NTSC format. The latter may be technically superior in those cases in which the signal is transmitted without phase variations (therefore, without the previously described color tone defects). But for that there should be ideal transmission conditions (without obstacles such as mountains, metal structures…) between the transmitter and the receiver. In any case where there are signal bounces, the PAL system has been shown to be clearly superior to NTSC (of which, in reality, it is a technical improvement). That was one reason why most European countries chose the PAL system, since the European orography is much more complex than the North American one (the entire Midwest is virtually flat). Another reason is that in the US. local broadcasts are common and in Europe national stations are common, whose stations tend to have a larger coverage area. In the only respect that NTSCis superior to PAL is in avoiding the flickering sensation that can be seen in the peripheral vision area when watching TV on a large screen (more than 21 inches), because the refresh rate is higher (30Hz in NTSC vs. 25Hz in PAL). In any case, this is a relatively new argument since in the 1950s the average size of the screen of a television receiver was about 15 inches, and this image refresh rate was also originally adopted conditioned by the frequency of alternating current in European countries, which is 50Hz compared to 60Hz in the US.

NTSC Vs PAL

The preformed concept that we have is that PAL IS MUCH BETTER THAN NTSC and it is still believed especially as far as DVD PAL vs. DVD NTSC is concerned, but some data that does not leave PAL as well planted as it was believed.

Some things to learn:

The PAL DVD image has more resolution than the NTSC DVD image, which is the concept that most people use to say that pal is better than ntsc, that is, 720×480 against 720×576 gives PAL the clear winner.

But since the pal image has more pixels, a higher compression factor must be used when it is compressed to mpeg2, so it loses more quality, while in ntsc the compression factor of each frame is lower, so it loses less quality. (Let’s say that they are half tied in this, after all it is difficult to decide between a frame with higher resolution but more compressed versus one with less resolution but less compressed)

NTSC, having 5 more frames per second, has better performance in scenes where there is a lot of movement on the screen or very fast movements in part of the screen and mpeg2 compression, having more frames, achieves better results in this type of scene. (so ntsc would win at least in that kind of scenes)

PAL is smoother because there is no repeated field pulldown. (for what pal wins)

When you go from the original film to PAL, the result is 4% accelerated with respect to the original, since cinema cameras work in 24 complete frames, so there is a lack of coordination between the image and the audio, but it is difficult to notice it with the naked eye. view. (so ntsc would be better) The PAL has more image flickering than the NTSC so it tires the eyes more (of course for it to bother you have to watch many hours) (so ntsc would be better)

PAL is more easily switched to progressive scan so if you have that system and a TV that supports it it’s better. (so it would be better pal)

PAL is preferable for dvd if we take out all the problems that it can give you in Argentina in particular, but pal was not as good as I thought.

Of course, when deciding what to use for your DVDs, you have to take many other factors into account.

One of its few advantages of NTSC is this:

On the other hand, NTSC systems offer the advantage of tiring the eyes less because they do not have the classic flickering of the PAL system operating at 50Hz/25FPS, instead NTSC works at 60Hz, tiring the eyes less, this is like comparing the flickering of a lamp or fluorescent tube to an incandescent bulb at present this problem was overcome with televisions that updated the image at twice the standard, that is, at 100hz.

Description of the idle part of the line in the PAL system

Previous portico

Duration 1.5 microseconds. Its primary function is to eliminate the electron beam in both the camera and the receiver, allowing the trace to return to the beginning of the next line. In segmented recording formats the switching between heads is done in the horizontal blanking interval. In the C and Quadruplex formats, the switching is carried out in the front port.

Horizontal sync or line sync

Negative pulse with an amplitude of 30% of the dynamic range of the signal, has a duration of 4.7 microseconds.

Edge of attack

The leading edge, or lead, synchronizes the panning of the monitor and the camera. In VTRs the leading edge is used to electronically identify the start of the blanking interval. It is also used in some TBCs to correct for large time base errors by comparing the demodulat or signal to the station reference. The “bottom” of the sync is used on some teams to set the correct level of DC. (On modern VTRs this is done with the back porch.) The trailing edge of the sync is used in VTRs to identify the beginning of the back porch and thus engage some circuits; it also serves to initiate the “Burst Gate Pulse”, which is used to discriminate color information.

Back porch

Allows blanking of the beam before the start of the active part of the line and isolates the beam return time. In VTRs it is used to reset the DC level of the signal after detection. In the VTR the corrections of the AFC circuit of the modulators are made here, because the signal is the same in all the lines. During the back porch, the RF of this part of the line (at the modulator output) is compared and corrected with respect to a quartz oscillator. 5.8 microseconds.

Burst

Duration 2.27 microseconds (10 +/- 1 cycles).
It is located on the back porch, and provides a constant phase (hue) and amplitude (saturation) reference for the receiver to correctly demodulate color information that is modulated on the line.
In VTRs it is used to establish what is recorded or reproduced in color, and activates the circuitry associated with these processes. Any high frequency noise that is located in the place of the burst can cause the color circuitry to be activated with the consequent distortion in the image. Since the burst should have constant phase and amplitude, and is a high-frequency component of the video signal, which is repeated on all lines, it is used during playback to determine if the demodulated signal is properly equalized.

Equalization

It is the process of changing the response curve of an amplifier to achieve a flat response when the amplification factor varies with frequency. This compensates for non-linearity in the playback of tape heads and materials. In modern VTRs it is automatic (Burst is sampled) Any variation in the frequency or phase of the burst during demodulation is a sign that the player has time base problems that require correction. The Burst is compared to a stable reference and the result is used to correct these errors. (If recorded in B/W, the leading edge of the horizontal sync is used for this)

Burst-flag

Approximate duration of 2.3 microseconds. It is a pulse whose leading edge is delayed by 5.6 microseconds from the leading edge of the horizontal sync, and is used to place the burst in the correct location on the back gantry.

Grades: VTR = Video Tape Recorder. In professional video technology, it refers to a machine that records baseband or component video at professional quality (typically the resolution of 16mm film or higher). TBC = Time Base Corrector. A TBC is a device that is responsible for normalizing the signal delivered by a VTR so that it can be used together with the signal from cameras and other electronic devices used in audiovisual production. This is necessary because VTRs are electromechanical devices and are exposed to drifts and operating irregularities typical of electric motors and, in general, of any mechanical device.

Overview of the PAL B/G television system

• Aspect Ratio: 4:3
• Number of lines: 625
• Active lines (effective vertical resolution): 576
• Active columns: 720
• Vertical blanking: 25 H + 12 microseconds
• Frame Rate: 25Hz (40ms)
• Field frequency: 50 Hz (20 ms, of which 18.4 ms active)
• Horizontal or line frequency: 15.625 Hz
• Equalization pulse frequency: 31,250 Hz
• Chrominance subcarrier frequency: 4.4336 MHz (Amplitude and phase modulated)
• P signal frequency (PAL): 7.8 kHz (1/2 line frequency)
• Line period (H): 64 µs
• Line active period: 52 µs
• Anterior gantry duration: 1.5 +/- 0.3 µs
• Back Porch Duration: 5.8 +/- 0.2 µs
• Horizontal sync duration: 4.7 +/- 0.2 µs
• Horizontal blanking duration: 12 +/- 0.3 µs
• Burst duration: 2.25 +/- 0.2 µs = 10 +/- 1 cycles
• breezeaway duration: 0.9 µs (Relative to trailing edge)
• Vertical pulse duration 27.3 µs (there are 5 pulses)
• Vertical sync duration: 160 µs (All five pulses)
• Equalizing pulse duration: 2.35 µs (there are 5 pulses)
• Vertical Front Porch Duration: 160 µs (contains 5 pre-EQ pulses)
• Vertical back gantry duration: 1,280 µs (5 pulses + 17.5 H)
• Vertical blanking pulse duration: 1.612 µs
• Burst start relative to 0H: 5.6 +/- 0 1 µs

The measurements are made at 50% of the amplitude of the pulses (Ref times)

• Rise and fall time of the pulses (From 10 to 90%): 0.2 +/- 0.1 µs
• Active video rise and fall time (from 10 to 90%): 0.3 +/-0.2 µs
• Illuminant D (X=0.313 / Y=0.329)
• Gamma value: 2.8 (precorrection)

Obtaining the luminance signal

R, G and B are defined as the components of red, green and blue. Y is defined as the luminance component. You have to:

Y(R,G,B) = 0.30R + 0.59G + 0.11B

Obtaining the chrominance signals

B, R, and Y are defined as the components of blue, red, and luminance, respectively. U and V are defined as the blue-difference and red-difference components. You have to:

U(B,Y) = 0.493(B – Y)

V(R,Y) = 0.877(R – Y)

Total bandwidth: 5 MHz
Bandwidth of U and V: 1 MHz