Talk:NTSC

Cleanup tag

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?

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)

NTSC / Television - Duplicate Effort

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

[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

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)

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)

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

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

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)

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)

Audio subcarrier? Looks wrong.

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)

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

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)

Phase is Hue - Amplitude is Saturation -- Not quite

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

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)

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

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

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

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)

I-Q vs RGB

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)

Where's Vietnam in the list of countries?

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

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)