Talk:NTSC

From Wikipedia, the free encyclopedia
Jump to: navigation, search
          This article is of interest to the following WikiProjects:
WikiProject Film (Rated C-class)
WikiProject icon This article is within the scope of WikiProject Film. If you would like to participate, please visit the project page, where you can join the project and see lists of open tasks and regional and topical task forces. To use this banner, please refer to the documentation. To improve this article, please refer to the guidelines.
C-Class article C  This article has been rated as C-Class on the project's quality scale.
Checklist icon
Taskforce icon
This article is supported by the Filmmaking task force.
 
WikiProject Media (Rated C-class, Low-importance)
WikiProject icon This article is within the scope of WikiProject Media, a collaborative effort to improve the coverage of Media on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.
C-Class article C  This article has been rated as C-Class on the project's quality scale.
 Low  This article has been rated as Low-importance on the project's importance scale.
 
WikiProject Color (Rated C-class, Low-importance)
WikiProject icon This article is supported by WikiProject Color, a project that provides a central approach to color-related subjects on Wikipedia. Help us improve articles to good and 1.0 standards; visit the wikiproject page for more details.
C-Class article C  This article has been rated as C-Class on the project's quality scale.
 Low  This article has been rated as Low-importance on the project's importance scale.
 


Cleanup tag[edit]

I asked User:Blaxthos if the article still warranted the cleanup tag and the response was

Thanks for the note. While the article has improved considerably in scope, I still think there are some problems with the article structure and tone. There's a lot of very technical information that should probably be confined to the Technical Details section, and a good portion of the article uses informal voice ("This is done by...", "You could think of it as...", etc.) The content on the whole is really good, it just needs some formalization.

--Wtshymanski (talk) 14:32, 26 January 2009 (UTC)

Video blanking interval: 19, 20, 21, or 22 lines?[edit]

The Lines and refresh rate section of the article states that that the NTSC transmission is made up of 525 lines, of which the following are visible:

  • 21–263: 243 even-numbered scanlines
  • 283–525: 243 odd-numbered scanlines

for a total of 243 + 243 = 486 visible lines.

I'm guessing that the remaining lines are:

  • 1–20: a 20-line vertical blanking interval
  • 264–282: a 19-line vertical blanking interval

Yet the Vertical Interval Reference section says that lines 1-21 of each field are used for the vertical blanking interval, and that sometimes line 22 is used as well.

I think a clearer statement of the allocation of all 525 lines is needed. — Wdfarmer (talk) 04:35, 23 February 2009 (UTC)

525 lines per raster. 21 lines of blanking per field. 2 x 21 = 42. 525 - 42 = 483 active scan lines (241 1/2 active lines per field). Line 21 is for closed captioning. Line 22 was suuposed to be for Teletext.

NTSC / Television - Duplicate Effort[edit]

There is an article, Television that has almost the same information. Why this duplication of effort? --Ohgddfp (talk) 23:28, 18 March 2009 (UTC)

Because it doesn't have almost the same information? --Wtshymanski (talk) 02:41, 19 March 2009 (UTC)

Well, I guess what I am saying is that there seems to be no rhyme or reason why some concepts are in one artible and some are in the other. --Ohgddfp (talk) 16:21, 20 March 2009 (UTC)

Knowledge Tree in the style of an Index[edit]

[NOTE: I use brackets for comments in order to differentiate those comments from suggested material.] [NOTE: My wording is not so good, and so I can use help at some point to make it much better.]

Video

[Use a common dictionary definition here] (See Video Signal)

Video Signal

A closed-circuit signal, which is a signal that is either inside a cable or inside an instrument such a TV transmiiter or TV receiver, that carries a single channel of changing graphical information such as a motion picture or radar image. This information is used ultimately for reconstructing the motion picture or changing graphic onto a viewing screen. The video signal supplies the information only in real time, as needed to update the viewing screen.
For motion picture television-like applcations, the moving picture is comprised of a series of still pictures (video frames) displayed one after the other in rapid succession at the rate of approximately 10 to 100 frames per second, giving the illusion of motion in the same manner as with motion picture film. The information of a given still picture (video frame) is delivered by the video signal only a short time before the viewing screen device uses that information to reconstruct that given still picture. This just-in-time frame-by-frame delivery of the information is called streaming. For analog broadcast TV, the delivery of a given frame is millesconds before it's displayed. For digital signals that are using digital image compression, pieces of a frame may be conveyed at slighty different times, requiring reassembly at the receiving end. This causes as much as approximately half second delay between the time all the pieces of a particular frame are sent, and the time it is displayed onto the viewing screen. This dealy in processing of the digital video information sometimes causes lip-sync problems. The frame rate for broadcast analog low-power TV in the United States is approximately 30 frames per second, while the frame rate for digital broadcast TV varies from about 23.97 frames per second to 60 frames per second.

Video Frame

A video frame is a still picture that is one of a continuous series of still pictures displayed in rapid succession to give the illlusion of motion. The information of a given still picture is ultimately used for reconstructing that picture onto a viewing screen.
Since a 2-dimensional still picture is really only variations of light over a flat surface, the picture can be electronically captured by a lens focusing an image onto the flat surface of an electronic image sensor that is covered with a sufficient number of light detectors (pixels) that together record the variations of light over that surface. The more light detectors there are, the closer the detectors are to each other, and the closer that neigboring light values can be located near each other while differences in their light values are still able to be resolved. This in turn allows the capture of details that are more finely (highly) defined. A video frame in a high definition (high resolution) system requires at least 1024 columns and 768 rows of pixels.
Monochrome (Black and White) Systems
Each light detector, called a picture element (pixel), converts the amount of light falling on it into a quantity of electricity. In this way, the information carried by the electrical quantity associated with a given pixel is the quantity of light falling onto that pixel.
A viewing screen consisting of many rows and columns of light sources, such as light bulbs or light emitting diodes, can reconstruct the image by connecting the individually amplified electical values of each sensor pixel to the correspondingly located display pixel. The brightness of the display pixel is detemined by the quantity of electricity applied to that pixel, which in turn was determined by the amount of light falling onto the correspondingly located image sensor pixel. So the variations of light are reproduced pixel by pixel over the entire surface.
The amplified electrical value of each pixel may be made available by switching the values onto a single wire, one pixel at a time. Alternately, the pixel values may be digitized and written to memory for later read out into a digital to analog converter, the output of which is also the amplified electrical value of each pixel. The reconstruction onto a viewing screen can be much more econmically carried out by transferring the amplified electrical value of each individual sensor pixel one at a time over a single wire that is connected to the display. In the display, each electrical quantity is electronically switched to the associated display pixel. Generally, the sensor pixel values are transferred row by row starting with the top row, and within each row, column by column. So the pixel values are read from locations in time order are like reading words on a page, left to right, starting at the top. For 1024 x 768 digital television, more than 700 thousand pixel values must be transferred for each video frame. With 60 video frames per second, that equates to more than 47 million light values tranferred each second for a black and white television program.

--Ohgddfp (talk) 16:14, 19 March 2009 (UTC)

This has got to be fixed. Serious questions of what is presently in the article[edit]

Article Section: Transmission modulation scheme

About "The highest 25 kHz of each channel contains the audio signal, which is frequency-modulated, making it compatible with the audio signals broadcast by FM radio stations in the 88–108 MHz band." I'm specifically referring to the later part of the sentence: "making it compatible with the audio signals broadcast by FM radio stations in the 88–108 MHz band." --Ohgddfp (talk) 15:46, 20 March 2009 (UTC)

What is the point of making TV audio compatible with FM stations? The sentence seems to imply that this is some kind of a benefit. What's the benefit? If there is no benefit, why even mention it? I'm sure that in some countries, the TV audio is AM, yet I'll bet the same country also has FM stations. See talk section: "250kHz Guard Band" ... Where it from? --Ohgddfp (talk) 15:46, 20 March 2009 (UTC)

About "The highest 25 kHz of each channel contains the audio signal ..." --Ohgddfp (talk) 15:46, 20 March 2009 (UTC)

This directly contradicts the graphic, which shows not 25 kHz, but more than 500 kHz containing the audio signal. Look at the part colored brown. See talk section: "250kHz Guard Band" ... Where it from? --Ohgddfp (talk) 15:46, 20 March 2009 (UTC)

About "A guard band, which does not carry any signals, occupies the lowest 250 kHz of the channel to avoid interference between the video signal of one channel and the audio signals of the next channel down" --Ohgddfp (talk) 16:14, 20 March 2009 (UTC)

What is the reference for this graphic? The FCC adopted NTSC's recommendations. Is this taken from an original NTSC document or from the U.S. Code of Federal Regulations, which legally govern these things? See talk section: "250kHz Guard Band" ... Where it from? --Ohgddfp (talk) 15:46, 20 March 2009 (UTC)
The guard band info is bogus. I Googled it and found the apparent source being a page that shows it and has no reference.
I just spent $51 USD of Comcast's money purchasing ITU-R BT.1700 and 1701-1 in order to debug an NTSC problem on one of our cable plants. The spec says nothing about a guard band. I've been studying and working with NTSC for about 40 years and have never heard of a guard band. What the spec does say is that the LSB aka VSB must extend no further than 750 kHz below the luminance carrier at full power, then must start to roll off, to a maximum power of 20 dB below the luminance carrier at the lower channel edge. It keeps rolling off to a maximum power of 42 dB below the luminance carrier at 3.5 MHz below the luminance carrier, which is way into the channel below. -- Liberator 10 (talk) 22:15, 14 May 2012 (UTC)

About "The actual video signal, which is amplitude-modulated, is transmitted between 500 kHz and 5.45 MHz above the lower bound of the channel." --Ohgddfp (talk) 16:14, 20 March 2009 (UTC)

This wording is really clumsy. Without the graphic, it's completely unintelligable. Better to just take it out. --Ohgddfp (talk) 16:14, 20 March 2009 (UTC)

"The Cvbs (Composite vertical blanking signal) (sometimes called "setup") is a voltage offset between the "black" and "blanking" levels. Cvbs is unique to NTSC. Cvbs has the advantage of making NTSC video more easily separated from its primary sync signals. The disadvantage is that Cvbs results in a smaller dynamic range when compared with PAL or SECAM."

This part of the present article is completely wrong. See talk section: "CVBS Error" on this page. --Ohgddfp (talk) 16:14, 20 March 2009 (UTC)

About: "A guard band, which does not carry any signals, occupies the lowest 250 kHz of the channel to avoid interference between the video signal of one channel and the audio signals of the next channel down" --Ohgddfp (talk) 16:14, 20 March 2009 (UTC)

Which version of NTSC mentions a 250 kHz guard band? I cannot find it in the only document that local broadcast stations are legally required to follow. That is "Title 47 (FCC) Part 73". See talk section: "250kHz Guard Band" ... Where it from? --Ohgddfp (talk) 15:46, 20 March 2009 (UTC)
See my comment above about the guard band. It doesn't exist. The whole concept is bogus. There is a specified rolloff rate of the LSB aka VSB, but no guard band. -- Liberator 10 (talk) 22:18, 14 May 2012 (UTC)

Article Section: History

About "In December 1953, it unanimously approved what is now called the NTSC color television standard (later defined as RS-170a).". But RS-170a only refines the timing specifications. It is not a redefinition of NTSC. See Talk section: History. --Ohgddfp (talk) 15:32, 21 March 2009 (UTC)

History[edit]

About "Color information was added to the black-and-white image by adding a color subcarrier of 4.5 × 455/572 MHz (approximately 3.58 MHz) to the video signal." --Ohgddfp (talk) 15:04, 21 March 2009 (UTC)

Well, the wording is confusing. I would say something like this (with even better wording than mine) --Ohgddfp (talk) 15:04, 21 March 2009 (UTC)
"Color information was added to the black-and-white image by modulating a 3.58 MHz color subcarrier with color-difference (colorizing) information, and then adding the result to the black and white video signal to produce a composite video signal. --Ohgddfp (talk) 15:04, 21 March 2009 (UTC)

About "In December 1953, it unanimously approved what is now called the NTSC color television standard (later defined as RS-170a)." --Ohgddfp (talk) 15:29, 21 March 2009 (UTC)

I'm talking here about the portion from the above that says, "... later defined as RS-170a ...". RS-170a is a proposed standard that was never officially adopted by any of the private standards bodies. The timing portion of this standard did however become industry practice never-the-less. --Ohgddfp (talk) 14:39, 25 March 2009 (UTC)

The timing portion of RS-170a does not contradict FCC regulations. Rather, it refines them so that subcarrier to horizontal phase is maintained to a particular standard so that videotape editing of composite NTSC does not suffer from "H-SHIFTS", where the entire picture jumps horizontally by maybe only a sixteenth of an inch at the edit point. When making match cuts, this was very annoying. RS-170a solved this whenever it was correctly put into practice inside the studio. A side-effect is that the resulting transmitted signal usually conformed to the timing portion of RS-170a as well, which is okay because it does not contradict federal regulations. --Ohgddfp (talk) 14:39, 25 March 2009 (UTC)

But some other parts of RS-170a may be contrary to federal regulations. I haven't seen the entire standard, but I will be getting it though library loans to see its general coverage. --Ohgddfp (talk) 14:39, 25 March 2009 (UTC)
So I would just take out the "(later defined as RS-170a)". In its place I would get a definitive reference for broadcast grade picture monitors, broadcast grade studio camera manufactures or broadcast grade telecine film chains that sell to the TV networks that one or more of the specs, either by conforming entirely to SMPTE-170M or entirely to RS-170A, or some other spec that is contrary to federal regulations (FCC rules). Broadcast grade was a signal from manufacturers to potential customer not just of some vauge picture quality performance level. Broadcast grade was, in my experience working as video engineer in facilites using network grade equipment, also a promise from the manufacturers that their product does not violate federal regultaions (FCC rules). And I'm talking here about the federal regulations (FCC rules) that were written by the NTSC. The first broadcast grade studio equipment sold to the networks that contradicts FCC rules would indeed signal a switch in industry practice to evading federal law. Another reliable signal of a switch is in the broadcast grade picture monitors that dropped the matrix switch with the circuitry operation the same as the matrix switch in the off position. My feeling at this time is that color space conversion from FCC primaries to actual physical screen primaries was always available in broadcast grade picture monitors. Indeed, I purhased an Ikegami broadcast grade studio picture monitor in 1990. It cost five-thousand 1990 dollars, had full I/Q demodulation, used SMPTE-C phosphors, and had the standard matrix switch the same as used on the Conrac monitors. While at the NAB in 1990, I looked at many camera demos. All the monitors used SMPTE-C phosphors with their matrix switches turned on, meaning the camera signal expected FCC phosphors (FCC primary colors). So we need reliable references of an actual change in industry practice toward lawlessness. Standards bodies may adopt standards, but that's not the same as industry following them in their entirety. We should only point out the camera and monitor specifications along with any contradictions to engineering specs authored by the NTSC. My own feeling is that the industry was indeed law abiding, but I guess I could be wrong at some point. Let's see the actual refernces of a shift in industry practice. Remember also that signals not bound for local TV transmitter have no legal requirment to conform to ANY NTSC variant, FCC or otherwise, and so there was a market of cheaper TV equipment ("consumer", "semi-pro", "industrial" that made no pretenses to following ANYTHING, except to be "NTSC compatible". And this is where a lot of confusion is coming from. So we will leave it up the readers themselves to decide if people should have gone to jail. --Ohgddfp (talk) 14:39, 25 March 2009 (UTC)

I could not find any other factual errors in the History section. --Ohgddfp (talk) 15:29, 21 March 2009 (UTC)

Backwards compatibility[edit]

Does anyone know how the backwards compatibility with black and white tv's works exactly? I've googled around but can't find a clear answer. Is it just because the older tv set's hardware naturally acted like a low-pass filter and ignored the high frequency chroma signal? If someone has a clear/simple answer to this, please add it to the article... —Preceding unsigned comment added by 69.247.172.84 (talk) 03:51, 10 July 2009 (UTC)

It is not simply because older TVs acted like a low-pass filter and ignored the high frequency chroma signal. It was actually some of the newer sets that did erase most of the chroma using low-pass filtering, but at the expense of reducing fine image detail. So the reality is that backward compatibility is due to reasons that are much more complex, as explained below. Ohgddfp (talk) 21:54, 20 September 2012 (UTC) Ohgddfp (talk) 04:26, 21 September 2012 (UTC)
All TV receivers low-pass filter the signal to minimize ringing (multiple ghosts on vertical edges), consistent with maintaining maximum fine picture detail. Additional (excessive) low-pass filtering, utilized to reduce receiver cost, improves compatibility slightly in one way, but only at the expense of reducing fine picture details. But some monochrome TVs do not have additional low-pass filtering, yet the compatibility is still excellent. And because of tighter specifications in the color broadcast signal, the monochrome pictures are even better with the color signal, even on those older sets that had no additional low-pass filtering. This means that other NTSC features working in a much more complex manner are at work to provide backwards compatibility. Ohgddfp (talk) 04:26, 21 September 2012 (UTC)
A little background infomation: In a color TV broadcast signal, the color composite video signal is carried by an RF carrier wave. Inside both color and monochrome receivers, the color composite video, with a frequency spectrum from zero to 4.25 MHz, is recovered from the RF wave, and is available on a single wire inside the receiver. Ohgddfp (talk) 04:26, 21 September 2012 (UTC)
The color composite video signal carries 3 kinds of information to convey every color in the scene. In the most general terms, this is Luminance, Hue and Saturation. Luminance conveys the lightness or darkness of a given color. Hue conveys which color, such as red, orange, green, purple, etc. Saturation conveys the strength of the color, from zero (gray, white), to weak (pale, pastel), to strong (vivid, electric, deep, rich, flourescent). Since Luminance conveys the lightness or darkness of a given color, it’s ideal for monochrome receivers. Indeed, the old monochrome-only TV signal attempted to convey luminance for that reason. So for backward compatibility, the composite color signal uses the old monochrome signal as its base. So to a monochrome receiverItalic text, the new composite color signal looks the same as the old monochrome-only signal. The composite color signal also contains "coloring" (Saturation and Hue) information, which the monochrome receiver interprets as minor interference that is almost invisible to the viewer, and is displayed in black and white. Ohgddfp (talk) 20:06, 22 September 2012 (UTC)
Following is an explanation of the complicated reasons why this above-mentioned "minor interference" is so difficult for the human eye to see. To convey the above-mentioned Hue and Saturation, a chroma signal is added to the old monochrome signal to make the new color NTSC signal, otherwise known as the color composite video signal. Ohgddfp (talk) 20:23, 22 September 2012 (UTC)
At first glance, Luminance, carried by both the old monochrome signal and the new composite color signal, seems to use the entire zero to 4.25 MHz frequency spectrum, so there is no apparent spectrum space available for combining the old monochrome-only signal (which carries Luminance), with the chroma (which carries Hue and Saturation) to make the composite color signal. Ohgddfp (talk) 20:23, 22 September 2012 (UTC)
But spectrum space actually is available. Some more background information is needed to understand why. Chroma is created by utilizing a 3.58 MHz subcarrier that is near the high end of the Luminance frequency spectrum. This subcarrier is modulated by the Hue and Saturation information to create sidebands. The subcarrier itself is then deleted, leaving the sidebands that carry all the Hue and Saturation information. These sidebands alone comprise the chroma signal. But the Chroma sidebands extend from 2 to 4.1 MHz, apparently overlapping the Luminance signal in that frequency range, and therefore causing crosstalk interference between Luminance and Chroma on the monochrome picture tube screen. Ohgddfp (talk) 04:26, 21 September 2012 (UTC)
The first method to improve backwards compatibility is to reduce this crosstalk by reducing the bandwidth of the Hue and Saturation information, since the eye is not sensitive to fine details in Hue and Saturation. This, combined with the choice of subcarrier frequency near the high end of the Luminance frequency spectrum restricts the frequency spectrum of the chroma sidebands from 2 to 4.1 MHz, also at the higher end of the Luminance frequency spectrum. The high relative frequency of chroma causes the interference to be a finely detailed pattern in black and white, making chroma more difficult to see in monochrome TV receivers. Ohgddfp (talk) 04:26, 21 September 2012 (UTC)
A second method is to take advantage of most objects not having much motion in most scenes, resulting in the Luminance frequency spectrum consisting mostly of harmonics of 30 Hz. The chroma subarrier frequency is chosen to be an odd multiple of 15 Hz, causing frequency interleaving, a major feature of color NTSC. This means that most of the time, 2.000010 MHz is a luminance harmonic, 2.000025 MHz is a chroma sideband, 2.000040 MHz is a luminance harmonic, 2.000055 MHz is a chroma sideband, and so forth. This alternation occurs from about 2 MHz to approximately 4.1 MHz. So in this way, it is seen on close inspection that Luminance and Chroma do not actually occupy exactly the same parts of the frequency spectrum most of the time. The chroma, already a finely detailed pattern, is seen, due to frequency interleaving, to reverse phase from one video frame to the next. The eye tends to integrate two successive video frames to average out the chroma on a monochrome screen, making the chroma even less visible, thereby improving backward compatibility. Ohgddfp (talk) 04:26, 21 September 2012 (UTC)
A further feature of NTSC frequency interleaving is that the chroma in time successive scan lines are also alternating phase, giving the chroma pattern appearing on a monochrome screen as a diagonal crosshatch pattern of dots instead of more visible vertical lines. Ohgddfp (talk) 04:26, 21 September 2012 (UTC)
Another NTSC feature to reduce chroma visability is that the chroma signal subcarrier itself is deleted. This means that only strongly colored areas of the scene have strong chroma (due to chroma sidebands), and such strong chroma is co-located with the strong color to prevent any mildly visible chroma from confusing perception of objects in the scene. Ohgddfp (talk) 04:26, 21 September 2012 (UTC)
So for backward compatibility, the chroma visibility is greatly dimished on the monochrome receiver by using a relatively high subcarrier frequency along with narrow band Hue and Saturation information, coupled with frequency interleaving, and the removal of the chroma subcarrier itself, leaving only the sidebands. Ohgddfp (talk) 04:26, 21 September 2012 (UTC)
However, the effectiveness in reducing the visability of chroma on a monochrome screen is not always perfect when viewed too close to the screen. On such close viewing, some people, especially trained observors, can see the chroma, which appears to be a finely detailed screenwire or dot pattern moving slowly upwards (crawling upwards) only in those parts of the scene that are strongly colored (high saturation). As a result, chroma, when visible on a monochrome screen, is called "chroma crawl” interference. Ohgddfp (talk) 04:26, 21 September 2012 (UTC)
Since the luminance signal is needed to define the lightness or darkness of a given color, color TV receivers need the same luminance information as do monochrome receivers, and therefore color receivers can also be subject to chroma crosstalk into the luminance, with the potential of creating the same kind of interference pattern as on a monochrome screen. The same NTSC features therefore reduce the visibility of chroma crawl on color receivers as well. Ohgddfp (talk) 04:26, 21 September 2012 (UTC)
However, the high amplitude of chroma on strong colors has the potential of reducing displayed color saturation due to the increased luminance resulting from the non-linearity of the picture tube. The chroma in the broad area of a strongly colored part of the scene must therefore be reduced further in amplitude inside the color TV receiver. The best way to accomplish this is to use a sophisticated filter that can be applied to the composite color video to “unmix” the chroma from the luminance. The best of such filters is a 3-d motion compensated comb filter, which takes advantage of NTSC’s frequency interleaving to separate the two signals. This keeps chroma out of the luminance while maintaining full bandwidth luminance to 4.25 MHz. In this way, the eye no longer has to play a major roll in reducing the visibility of chrominance. The chroma, now separated from the composite color video, is further processed to provide the "coloring" (Hue and Saturation) to the black and white picture, yielding the full color image. Ohgddfp (talk) 20:06, 22 September 2012 (UTC)
Ideally, monochrome receivers should also use such a comb filter, but none ever did due to the fact that monochrome receivers are supposed to be relatively inexpensive. Ohgddfp (talk) 04:26, 21 September 2012 (UTC)
Older color TV receivers made from 1954 to 1969, and newer "low-end" color TV receivers get rid of chroma from the luminance by using a notch filter set to 3.58 MHz. In a given highly colored object in the scene, this nearly obliterates the chroma from the luminance in the interior region of the object, but does not remove it from the left and right borders of that object. The end result, since the Saturation and Hue do not have sharp left to right transitions anyway, is that the color saturation of the object is maintained throughout the object interior. This method was relatively inexpensive, and decreased luminance video rise and fall times only by a relatively small amount. This is important because all human perception of finely (highly) defined small picture details comes only from the luminance information. The end result was still high quality pictures. However, areas with sharp and extreme left to right color transitions across the borders of strongly colored object did exhibit noticable chroma crawl on those borders when viewed up close. Ohgddfp (talk) 04:26, 21 September 2012 (UTC)
More below on frequency interleaving Ohgddfp (talk) 04:26, 21 September 2012 (UTC)
The color subcarrier is an odd half multiple of the line rate and frame rate. That means that the dot pattern cancels between successive lines and successive frames. If you look at in in spectral space, it is like a comb with the video interleaving the subcarrier, as the video signal tends to have compenents that are multiples of the line rate, while the color subcarrier is at odd half multiples of the line rate. While some may have a low bandwidth video amplifier, there is no reason that should be true. Gah4 (talk) 04:27, 19 November 2010 (UTC)
The signal looks to the black and white receiver just like a black and white signal. The colour subcarrier will be resolved as video information if the receiver has the bandwidth to process it. The result is that the colour subcarrier will appear on the picture as a fine dot pattern. However the amplitude of the colour signal is such that the pattern will only really be noticeable if you are too close to the set. Most viewers just won't notice it. In Europe, the colour subcarrier was deliberately chosen to outside of the specified video bandwidth so should be invisible, but I believe this was not the case in the US. 20.133.0.13 (talk) 09:05, 21 September 2009 (UTC)
I split System M into its own article a while ago, but I don't know if it helps. It's actually more a spin-off from this article; I created it because the current NTSC article really doesn't make much of a distinction, even though there's PAL-M also. --Closeapple (talk) 08:10, 22 September 2009 (UTC)
Ohgddfp claims that the NTSC standard deletes the chroma carrier, leaving only the sidebands. If this is true, how does an NTSC supposed to show a large solid colored area instead of just colored edges? — Preceding unsigned comment added by 76.202.253.136 (talk) 23:17, 28 October 2012 (UTC)
As President Nixon used to say, "I am glad you asked THAT question". I will speak about the "active portion" of the video signal, which does not include blanking, sync, or the subcarrier burst, which is found only within the blanking portion. To answer the question directly, a solid color filling more than half the screen will always show a frequency at exactly the subcarrier frequency on the spectrum analyzer. But even though this is the exact same frequency as the subcarrier, it's still technically a subcarrier sideband and not simply the subcarrier. Let me explain. Chroma, which is the shortened nickname for the subcarrier sidebands, carry I/Q information (for rendering saturation and hue), while the subcarrier itself carries no information at all. Hence, the subcarrier sideband content changes with scene content, the amplitude of the subcarrier itself is always constant. With NTSC, the subcarrier has a constant value of zero. In other words, NTSC deletes the subcarrier before transmission, but allows a subcarrier sideband at the exact same frequency as the subcarrier to come through. But the phase of the subcarrier sideband varies with scene content, and the amplitude of this "sideband" can also go to zero on some colored scenes. This is why it becomes necessary to transmit a "burst" of subcarrier, so that the receiver can reconstruct the subcarrier. The reconstructed subcarrier never appears in the video, but instead is used to recover the original I/Q signals from the subcarrier sidebands. It's the I/Q signals that add color to the monochrome image.
What the questioner is alluding to is one possible subcarrier "sideband", which carries the DC component of the I/Q signal. It just so happens that this "sideband" frequency is the exact same frequency as the subcarrier itself, and therefore shows up on a spectrum analyzer at the subcarrier frequency. But it's only a subcarrier sideband, because its amplitude varies with changing scene content. On some scenes, the I/Q signals might have no DC component, and the spectrum analyzer will respond by showing no energy at the subcarrier frequency. (When looking at this phenomenon with a spectrum analyzer, remember to electronically key out the blanking, leaving only the active video. Otherwise the burst, which has most of its energy at the subcarrier frequency, will show up on the analyzer, confusing the issue.)
Occasionally, some scenes have no DC component of I/Q at all, and therefore the subcarrier frequency is completely gone during the televising of that scene. Here is an example: There is a large solid object with a +Q color (a violet-like hue), and in the same scene, another identical object with a -Q color (a yellowish green hue). Both colors happen to have the same signal amplitude, just opposite polarity of the signal. These two colors are also complementary colors. So in this example, the subcarrier frequency is completely gone. So the subcarrier itself, which is always zero, does not change according to scene content, while a subcarrier "sideband" indeed does change according to scene content.
This approach of eliminating the subcarrier reduces the average amplitude at the subcarrier frequency, reducing the possibility of visible interference between chroma and luminance, and increasing visibility viewed close to the screen, only within objects that are strongly colored. If the subcarrier were to be transmitted, an interference pattern would almost always cover the entire screen, even when a given scene has no color at all. Ohgddfp (talk) 14:30, 15 August 2013 (UTC)

Audio subcarrier? Looks wrong.[edit]

In the Color Encoding section, the last paragraph uses the term "audio subcarrier" several times. The audio has its own carrier, but intercarrier audio (which just about every NTSC receiver had) uses one common IF amplifier chain for both video and audio (at least, it did in tube days). Audio is recovered at 4.5 MHz from the demodulated video, iirc, so, in a sense, at the demodulation stage, it's akin to a subcarrier; however, this paragraph needs rewriting slightly, I think. I didn't want to change it, because I'm not totally sure about what I believe to be true.

{For some reason, previewing this text as originally typed rendered it on one quite-long line, requiring scrolling to read it. I added line breaks.}

Regards, Nikevich (talk) 07:38, 24 November 2009 (UTC)

About "audio subcarrier". If, in transmission, you modulate the visual carrier with a frequency modulated 4.5 MHz audio subcarrier, along with the video itself, you separately get the AM visual carrier with sidebands containing picture information, plus an FM carrier with sidebands containing audio information. The FM carrier on the air is 4.5 MHz higher than the visual carrier. The original 4.5 MHz FM sound carrier (its sideband near 4.5 MHz), completely disappears on the air. Although this process can work with extremely linear amplifiers, it is just not done for full power commercial TV transmitters, due to the perfection needed for amplifier linearity so that beats don't appear. They instead use two separate transmitters, one for sound, the other for picture. At the receiving end, whenever the entire TV signal is presented to the input of an AM detector, the detector output is the video signal, plus a frequency modulated 4.5 MHz audio subcarrier, even though no such 4.5 MHz carrier is ever on the air. Older receivers in the forties would filter out the upper frequencies for the video channel, so that the AM detector was not presented with the full TV signal, but only those frequencies related to video. As a result, no sound subcarrier was on the output of the AM detector. Likewise, only the highest frequencies of the TV signal were presented to the input of an FM demodulator, which had only the sound signal as output. In the intercarrier system, the entire TV signal, not just the video related frequencies, are presented to an AM detector, where the visual carrier is much stronger than the frequencies related to the sound. As a result, the 4.5 MHz FM sound subcarrier with sidebands appears for the first time. Note that this FM sound subcarrier (with sidebands) must still be presented to the input of an FM detector in order to recover the audio signal. So "sound subcarrier" is legitimate, since it is physically indistinguishable from "4.5 MHz sound I.F." Ohgddfp (talk) 20:36, 1 February 2014 (UTC)

I want to buy a new led TV from the states and send it to Egypt will it work? —Preceding unsigned comment added by 173.58.216.194 (talk) 01:56, 18 May 2010 (UTC)

History: CBS system[edit]

How come the early CBS system had 24 effective frames/sec but 144 fields/sec? Did it split each frame into 144 / 24 = 6 fields? That's the logical explanation to me, but the way it's written now, it seems a bit obscure and confusing, so the section would probably benefit from adding that fact if it's true. --79.193.57.210 (talk) 21:00, 8 June 2010 (UTC)\

How about compare CBS with French television channels. Compare NBC with England television channels. Compare ABC and FOX with German television channels. Are the frozen pictures look any opposite? --DuskRider 08:33, 5 December 2012 (UTC)

Phase is Hue - Amplitude is Saturation -- Not quite[edit]

About this portion of the article: "The phase represents the instantaneous color hue captured by a TV camera, and the amplitude represents the instantaneous color saturation."

This is not completely true.

Below are some concepts that can help guide the search for more reliable sources of information to put into the article.

If only the chrominance signal (which is the MODULATED subcarrier with the subcarrier itself suppressed), is examined on a vectorscope, one can readibly see amplitude and phase for various colors. But the amplitude provides zero quantifiable information on how much a given color is saturated. ZERO. At best, one can examine the NTSC spec and figure out that the acutal saturation of a given color, based only on what's seen on a vectorscope is within some VERY WIDE RANGE of possible saturations. That's because it's the COMBINATION of the Y (brightness or monochrome) signal and the subcarrier amplitude that most determines the actual saturation.

And gamma must be taken into account as well.

Furthermore, hue often shifts noticibly when only the subcarrier amplitude is changed a great deal. And we are talking IDEAL HARDWARE here. The discrepencies are a mathematical consequence of the NTSC specifications, not hardware imperfections.

One of the things that can be said for sure is that an increase in subcarrier amplitude will cause an increase in saturation, provided that the color on the display screen is not already at the maximum saturation that the display screen primary colors can support.

So here's a better way to put this: "Regarding the subcarrier, the phase represents the approximate instantaneous color hue, and the amplitude, COMBINED WITH THE EFFECTS OF THE Y SIGNAL, represents the approximate instantaneous color saturation. Ghidoekjf (talk) 22:49, 9 July 2010 (UTC)

Technical Details -- Power Supply Frequency and Intermodulation[edit]

About the article - Technical Details --> Lines and refresh rate --> 2nd Paragraph, where it says

"Matching the field refresh rate to the power source avoided INTERMODULATION (also called beating), which produces rolling bars on the screen."

The problem is the term INTERMODULATION. Another problem is what happens to the "rolling bars" with the color system, since the field refresh is no longer matched to the 60Hz frequency of alternating current power. Although some measure of intermodulation always occurs, and certainly a large measure of intermodulation occurs when the "rolling bars" are SEVERE, due to at minimum the non-linearity of the picture tube, intermodulation is NOT REQUIRED for producing a MILD "rolling bars" beat pattern. And mild is certainly the most likely by far. The example of "rolling bars" and beating was mentioned only for black and white, but not mentioned for color. So I'll mentioned it here. 60Hz minus 59.94Hz = 0.06Hz, where 0.06Hz is the frequency of the beat pattern for color service. Although the beats really do occur at the 0.06Hz rate, this does not mean there is a substantial 0.06Hz FREQUENCY COMPONENT when there is a "rolling bar" that takes 8 seconds to crawl from bottom to top. The 0.06Hz "rolling bars" frequency component for color can only occur with intermodulation, and if there is no substantial degree of 0.06Hz component, then there is also no substantial intermodulation either in the case of MILD rolling bars. Instead of intermodulation, the effect of MILD rolling bars is due almost entirely to simple LINEAR addition of the 60 or 120 Hz power supply ripple to the video signal. And intermodulation requires NON-LINEAR, not LINEAR combination. So change the article to REMOVE the term INTERMODULATION, thereby improving the accuracy of the article. Ghidoekjf (talk) 16:19, 8 August 2010 (UTC)

If the power supply filtering isn't so good then line frequency, or a multiple of line frequency, comes through into the video signal and is visible. For this reason, the power supplies for color TV had to be better than previously needed for B&W only. Though .06Hz is slow enough not to be so noticable. Gah4 (talk) 04:34, 19 November 2010 (UTC)
Actually, intermodulation isn't the main problem. The CRT is sensitive to external magnetic fields such as from nearby transformers or motors. By making the frame rate equal to the power frequency, although the effect isn't eliminated, it as at least stationary and thus goes unnoticed. The slight change of frame rate with the introduction of color ceased to be as serious a problem because the increase in accelerating voltage significantly decreased the sensitivity of the CRT to magnetic fields. Thus the effect of external fields became far less noticeable. A further improvement is obtained because color CRTs usually have a limited amount of magnetic shielding. 86.176.154.127 (talk) 18:10, 21 January 2011 (UTC)
The external magnetic fields do not produce a moving shadow effect ("rolling bars"). Instead, they affect the scanning beam positioning as to bend the image slightly, and this bending effect moves vertically at the same rate as genuine "rolling bars". Also, the ocsillating magnetic fields can cause rolling color impurity as well, also at the same rate as rolling bars. But this issue is "rolling bars", which is a video shading effect, not affected by magnetic fields. Bending can also happen if power supply ripple gets into video circuits ahead of the sync circuits. It's the disturbance of those horizontal sync circuits that causes the geometric bending. Therefore, magnetic field problems causing some distubance of some sort are limited to design issues of transformers too close. In service, a failed automatic degausser circuit applies some degausing all the time, which is also a magnetic disturbance. Conclusion: Magnetic fields are indeed the more difficult design issue, but with internal power transformer too close, not by external ocillating fields, except for a nearby vacuum cleaner motor. The "rolling bars" are a video moving shadow effect, potentially a design or component failure issue equal to monochrome or color, although color TV's have a bigger power supply. Ohgddfp (talk) 04:40, 21 September 2012 (UTC)

Color correction in studio monitors and home receivers - Article is right on[edit]

This section in the article looks very good. I guess this is not really an edit. Ghidoekjf (talk) 16:29, 8 August 2010 (UTC)

Color Encoding -- Discretization[edit]

About -- Technical Details --> Color Encoding --> 3rd paragraph (towards end), where it says,

"This process of discretization necessarily degrades the picture information somewhat, ..."

This is not true.

Here is what I expect to be found from a good source. Transferring back and forth between discrete samples and a continuous signal is a LOSSLESS operation. Of course, any kind of operation done in a sloppy manner will cause degradation, but that's true for ANY operation. That means it's POSSIBLE for the analog tuner section of a modern flat panel LCD receiver to recover the original pixels from a modern video camera imager, all within the NTSC standard for low power analog transmissions still on the air. Here's how it would work, just as an example to illustrate the concept. Use a video camera with a hypothetical 448x483 imager. ("rectangular pixels"). The imager samples are processed into a composite video signal at the same sample rate (different from subcarier). The pixels now also contain the subcarrier sidebands (chroma). Then low-pass filter (flat within the entire video band) so that indeed the horizontal pixels are blended into continuous lines, then transmitted, and received. The analog tuner section of the receiver resamples at the same rate, using burst as the clock input to a sample reference generator, where the sample reference is different (and higher) compared to the subcarrrier frequency. There are other details that need to be insured, but still within FCC NTSC specs. The result is a complete and exact replication of the original camera pixels as far as black and white movies are concerned. The exactness limited only by practical hardware, not the NTSC standard. For color video, color difference information is still bandwidth limited and other NTSC artifacts are also still intact. Of course inside HD displays, a digital resample and upconversion is needed. Sorry, no additional resolution or picture definition by upconverting NTSC to HD.

So discretization, whether the vertical scanning lines of NTSC, or both vertical and horizontal for digital TV, does not necessarily cause picture quality degradation.

Recommend to simply remove the article phrase containing the word "degrades". Ghidoekjf (talk) 17:33, 8 August 2010 (UTC)

Comparative quality - Differential Phase Cannot happen as a Reception Problem[edit]

About - Comparative quality --> 1st paragraph, where it says, "Reception problems can degrade an NTSC picture by changing the phase of the color signal (actually differential phase distortion), ..."

The problem is equating "differential phase distortion" with "reception problems". "Reception problems" sounds like issues that occur in the air between the transmit and receive antennas.

But "through the air" reception problems are limited to 1) Signal that is too weak. 2) Interfering signals linearly added to the desired signal, and 3) Multipath.

Multipath, which alters the reception strength (amplitude) versus frequency and the phase versus frequency, and sometimes also nulls out some frequencies, is a form of LINEAR distortion, and is caused by obstacles and reflections in the signal path from transmit antenna to receive antenna. Differential phase distortion on the other hand is NON-LINEAR, and so cannot happen in the air. It happens mostly in older TV transmitters, and also in poorly designed TV receivers near overload condition.

So a transmitter defect (differential phase distoriton) is not really a "reception problem" at all as the article implies. And an overloaded tuner (from a strong signal) is not the fault of reception conditions either. Certainly a signal that is very strong is not thought of as a reception problem.

What can be said is that NTSC is more visually sensitive than PAL to both differential phase distortion and to multipath. With NTSC, multipath can produce additional hues not present in the original. Ghidoekjf (talk) 21:39, 8 August 2010 (UTC)

So how do you explain the shift in phase of the hue vector between different stations on reception? All the colors of similar luminance shift by the same phase shift which can only be explained by differential phase distortion. 86.176.154.127 (talk) 18:03, 21 January 2011 (UTC)
About "shift in phase of the hue vector ...": There is no such thing as "shift in phase of the hue vector". Phase is a comparison between two signals. With NTSC, the two signals are 1)The reconstructed subcarrier inside the receiver, made from the "burst" portion of the incoming signal, and 2) The "chrominance" portion of the "active" video signal. Between 1) and 2) above, sometimes the phase relationship between those two signals are different between multiple stations broadcasting the same program, and I think this is what you are asking about. The cause is mostly improper technical operation at one or both TV stations. Some of the cause can be differential phase problems ( a form of non-linear distortion), most of which is in some videotape playback and some transmitters to some hopefully small degree. It can also occur if one or more of the received stations is onverloading the tuner because the signal is too strong. It can never occur in the air.
Ohgddfp (talk) 17:13, 13 September 2012 (UTC)

I-Q vs RGB[edit]

Why no mention of the I-Q components of the color subcarrier, their respective bandwidths, and the matrix bewteen them and the (B-Y) (R-Y) components. Gah4 (talk) 04:37, 19 November 2010 (UTC)

Because you haven't had time to write it up yet, with references? And maybe even a diagram? Pretty please! --Wtshymanski (talk) 14:48, 19 November 2010 (UTC)
This is a glaring omission. The article needs to explain how we get from R, G, B to R-Y, B-Y and then to I and Q. — Preceding unsigned comment added by 65.197.211.2 (talk) 00:27, 8 August 2012 (UTC)
Here is an explanation that can help with a search for sources. It should help to discern between good an bad sources.

The NTSC standard converts RGB video signals carried on 3 wires into a composite signal carried by 1 wire (see below on how this is done). At the receive end, the process can be reversed to recover the 3-wire RGB video signals. At the transmit end, NTSC also describes how to amplitude modulate a carrier wave with the composite signal to create an RF signal. NTSC further describes modifying this RF signal with special filtering, including phase correction and vestigial side-band filtering, although low-power stations do not require all this special filtering. The filtered RF signal is then sent to the transmit antenna.

Now to describe how the RGB 3-wire signals are converted into a 1-wire composite signal. First the RGB signals are converted into 3 new signals, also carried on three separate wires. These are Y, I, and Q. The Y is approximately the lightness or darkness of colors, and so this also serves as an excellent black and white signal for compatibility to black and white receivers. It is created by adding the RGB signals together in the following proportions:

Y = 0.30R + 0.59G + 0.11B

The I and Q signals do a similar combination of RGB signals, but in radically different proportions:

I = 0.4370R - 0.4366G - 0.1589B

Q = 0.2130R - 0.5251G + 0.3121B

The above I and Q formulae were alebraically manipulated from the FCC formulae given below. Both versions give the exact same results.

I = -.27(B-Y) + .74(R-Y)

Q = .41(B-Y) + .48(R-Y)

Note that most of the Internet and even several "NTSC" standards document use numbers never written by the NTSC. Such equipment will produce incorrect colors when NTSC equipment using non-NTSC numbers is combined with NTSC equipment using numbers actually written by the NTSC. An example of a mis-match is receivers using non-NTSC numbers that receive a signal transmitted using genuine FCC numbers. Note that the NTSC (National Television Systems Committe) wrote the numbers adopted by the FCC for over-the-air analog broadcasting. The numbers given here are those FCC numbers actually written by the NTSC.

The Q signal must be bandwidth limited to prevent crosstalk with the wider bandwidth I signal after modulation. This modulation process is quadrature ammplitude modulation of a 3.579545.4545... MHz subcarrier, with I and Q as the two modulating signals. The subcarrier itself is removed, leaving only the subcarrier sidebands, which carry all of the I and Q information. The NTSC limits of the above-mentioned filters are given in the FCC rules. There is a lot of equipment made over the years that violate these filter limits.

The quadrature amplitude modulated ("called chroma") signal is then simply added to the Y signal to form the (1-wire) composite video signal. But the frequency band of the chroma signal occupies the same general frequency band as the high end of the Y signal, causing mutual crosstalk. Note the high end of the Y signal carries only small picture details, and the chroma signal carries the I/Q information. The frequency of the subcarrier is chosen to make this crosstalk much less visable to the human eye.

The Y signal serves as a black and white picture, directly usable by black and white receivers. The crosstalk of chroma into the Y signal is seen in some black and white receivers as a monochrome screenwire pattern on strong colored areas of the image. Of course, all these patterns are seen in black and white on black and white receivers. Fortunately, these crosstalk patterns are hard for the eye to notice. Older 50's black and white receivers show stronger crosstalk, but still is not bothersome. Black and white receivers otherwise ignore the chroma signal.

This same Y (black and white) signal serves as the base black and white picture in color receivers as well. As in monochrome recievers, this Y signal is also contaminated with chroma, and is fortunately hard for the eye to notice much. The chroma contains the "color difference" information derived from I/Q information carried by chroma. Chroma and fine detailed Y is applied to a chroma demodulator to recover I/Q signals that are contaminated with fine detailed luminance. This fine detailed luminance creates false colors in the demodulator. Fortuanely the false colors alternate from one video frame to the next with the complementary color. The eye mostly averages out this false color, another clever feature of NTSC. Occasionally this trick fails and wierd colored rainbows dance through portions of the image.

The recovered I/Q comprises the color difference image, which is superimposed over the black and white picture to produce a complete color picture. This process is used on the Internet as well, and is similar to painting a black and white picture with transparent water colors to "colorize" the black and white image. The I/Q signals provide these transparent "water colors" which are always all the same lightness. So mostly, the underlying black and white signals are what provide the lightness and darkness of any given color.

R-Y and B-Y signals are optional. R-Y is made simply by adding the inverted Y signal to the R signal. This can be done precisely with just 2 resistors. B-Y can be made in a similar way. At the transmitting end (ususally inside a video camera), the R-Y and B-Y signals can be created first, then the FCC formula can use them to make I and Q. Or R-Y and B-Y can be dispensed with completely and the alternate I and Q formulae can be used to get the exact same results.

Note that a special feature built into the system allows the option of simplified recovery of R-Y and B-Y signals in the receiver using in-phase and quadrature subcarrier signals. They can then be simply combined with the Y signal to recover the R and B signals for the picture tube guns. But the G signal still needs to be made from matrix circuits, or else G-Y can be recovered directly using the more complicated non-quadrature version of the subcarrier. Then G-Y can be combined with Y to get the G video signal for the picture tube.

Another simplification by using R-Y and B-Y signals in the receiver is to get rid of the I bandpass circuit and to also get rid of the I delay line. The I delay line was once made with coils, capacitors and resitors. A problem with receivers simplified in this way is that some colors (skin tones, orange, cyan) have only one-third the horizontal resolution compared with genuine I/Q demodulation. Almost all receivers however are of this simplified design.

R-Y / B-Y signals are easier than I/Q signals to generate in cheaper TV cameras (industrial and consumer grade), and work well for simplified lower quality "NTSC-like" signals, ususally called "NTSC compatible", where the filters can be simplified or even removed entirely, with attendant reduction in picture quality. Signals made with these simplified processes are often considered illegal for over-the-air broadcasting. In particular a genuine I/Q receiver (1985 RCA Colortrack series, for example) will produce annoying crosstalk effects when receiving such simplified NTSC signals.

Ohgddfp (talk) 20:30, 14 September 2012 (UTC)

I agree, this would be a nice addition. I was pondering quite a while how the luminance and chrominance bands can overlap without cross-talk. In addition to the above very detailed explanation I found some useful info at Composite video about how the chosen sub-carrier frequency of the chroma information minimizes the cross-talk. In particular, that the harmonic components of the luma and chroma signals are - mostly - non-overlapping. I still don't understand how the luma signal ends up being composed of the line frequency's harmonics though ... Explaining all this - perhaps with a frequency domain diagram - would be very useful. I'm not an expert, so I wouldn't do this myself. Seipher (talk) 23:04, 11 July 2013 (UTC)
About: "I still don't understand how the luma signal ends up being composed of the line frequency's harmonics though". There are indeed strong harmonics of the line frequency present in a luma signal. But this is indeed hard to understand because the line frequency is itself the 525th harmonic of the frame frequency. The luma signal is actually composed of the frame frequency's harmonics, which include the line frequency itself, and also harmonics of the line frequency. Line frequency harmonics are therefore harmonics of both the frame frequency and the line frequency, simultaneously. Keep in mind that this is strictly true for scenes containing no motion. This is substantially true most of the time because most scenes do not contain a lot of motion. For scenes with a lot of motion, the luma signal can contain any frequency, which is guaranteed to cause problems with luma/Chroma separation inside the color receiver. Note that the chroma is composed of harmonics of 14.985 Hz. Yes, you saw this number here first. These chroma harmonics start at about 2 MHz (for FCC compliant broadcasts), and continue up to about 4.1 MHz. Ohgddfp (talk) 15:59, 26 November 2013 (UTC)

Where's Vietnam in the list of countries?[edit]

In the SECAM article (and in other publications, such as the WRTH), Vietnam is always shown as having both SECAM and NTSC used for colour TV - the SECAM article says it is "simulcast with NTSC-M". Presumably, NTSC is used in the former South Vietnam and SECAM in the former North Vietnam. So why is there no mention of it in the NTSC article? --108.12.198.48 (talk) 01:33, 31 July 2011 (UTC)

South America[edit]

Is it really accurate to say that most of South America used the NTSC system? While it seems that the majority of south American countries adopted the standard, the map shows that geographically the majority was PAL. Did the majority of viewers on the continent receive NTSC? (My apologies if this has been raised before; I haven't read through the entire talk page) Stanstaple (talk) 18:59, 16 August 2011 (UTC)

Ireland[edit]

There were no colour tests in Ireland using NTSC on 405 lines at all. Suggest the link to Ireland is removed. Donoreavenue (talk) 00:19, 20 May 2012 (UTC)

PAL acronym =[edit]

My favourite interpretation of PAL is Please All Lobbies which it needed to do to become pan-European, except France.

Upcoming Fix - Discretization[edit]

About "This process of discretization necessarily degrades the picture information somewhat, though with small enough pixels the effect may be imperceptible.": Where is the source? We need to find a reliable source for this. Otherwise, I will delete the above quote from the article. Or, ....... not. So here's my argument. From sources on this subject over the years, I've found that discretization is a lossless process, meaning that, unlike that for many other kinds of operations where mathematically, there exists a minimum degree of degradation, discretization has no such minimum degree of degradation. In other words, with discretization, as with many other kinds of signal processing, there is no mathematical limitation as to how small the degradation can be.

So in NTSC, degradation caused by discretization can be minimized to any desired degree through hardware improvements. But that can be said about almost all operations. So why single out discretization? This is not an NTSC problem in reality. It gives weight to something that, due to hardware imperfections, is no worse than just about any other signal processing operation. Giving such weight to something without a good source to back it up only confuses the reader. Since this is actually in the realm of mathematics, I am waiting for a mathematical proof from a reliable source, that discretization "necessarily degrades the picture information somewhat". Since this is a mathematical issue, the source must be compatible with mainstream science. - A source, anyone? Ohgddfp (talk) 02:06, 13 December 2013 (UTC)

The section on colour encoding needs to be looked at by someone who really knows this subject well. The lower half of this section has some pretty specious explanations about scanning rates, dot patterns and sound IF frequencies. For starters I don't think these topics should be in the article at all. How is Mr Average supposed to understand any of this Gobbledygook? Spyglasses 10:31, 1 February 2014 (UTC) — Preceding unsigned comment added by Spyglasses (talkcontribs) ---

China uses PAL, not NTSC[edit]

According to [1], China uses PAL D, not NTSC. I also have a old Sharp chart showing the system of the World showing the same thing. I would like to propose that China be moved from NTSC to PAL. RAM (talk) 02:22, 6 March 2014 (UTC)

Uhh... what?[edit]

Quote:

"

This standard is slowly being replaced by HDTV.

"

HDTV (high-definition television) is not a "standard", it is an ambiguous comparitive term describing the resolution of nearly any video mode. NTSC is not being "replaced by HDTV", it is being replaced by newer video systems that support high-definition modes. Once upon a time, 405-line television System A was once considered "high definition" compared to the previous 30-line Baird system, as the later 625-line system was to A.