Talk:Composite video

Under Section Modulators

"...many TV sets sold these days no longer have analogue television tuners and cannot accept channel 3/4." Is there a shred of factual data to support this? Except for the brief blip in time around 2005 when "monitors" without built in dual NTSC, or ATSC or Clear QAM tuners I can not find the above quote to even to this day be a true statement as an AVID TV purchaser / shopper. — Preceding unsigned comment added by 66.188.252.171 (talk) 13:21, 8 July 2014 (UTC)

I know it is true for DVD recorders. They stopped putting in NTSC tuners, and mostly didn't put in ATSC tuners. For cable users with a converter box, there is no need for any tuner. Presumably there is a phase out, but I don't know how fast. Gah4 (talk) 18:53, 17 August 2017 (UTC)

Illustration

Would it be possible if someone made an illustration or graph of how it is done getting 3 signals (YUV) in one "plug" with only 2 connectors? I'm very curious about that, atleast, but dont nearly have enough background knowledge to do it. anon 10:56, Jun 17, 2010 (UTC)

Diagram

The voltages in the diagram are all wrong.

In U.S. NTSC, blanking is at 0 volts (0 IRE), the sync tips are at -0.286 volts (-40 IRE), and peak white is at +0.714 volts (100 IRE). The peak-to-peak amplitude is 0.286 + 0.714 volts, or one volt. Setup (pedestal) is +0.05355 volts (7.5 IRE). — Preceding unsigned comment added by Chris319 (talk • contribs) 06:11, 14 July 2017 (UTC)

The diagram is showing a one-volt signal. I'm not sure how important it is to set the bottom reference at 0v vs. -0.286v. Also we need a source. ~Kvng (talk) 17:03, 25 April 2021 (UTC)

Initialisms

In the 60's/70's some wag came up with some alternate words for the abbreviations:

• NTSC "Never Twice the Same Colour"
• SECAM "System Essentially Contrary to the American Method"
• PAL "someone please fill this in and check" "Perfection All Lines"? <-- "Picture at Last"

If I remember right it was heavily biased to PAL Archivist 00:55, Nov 15, 2003 (UTC)

I knew SECAM as "Shows Every Colour All Murky"

20.133.0.13 (talk) 14:05, 24 March 2009 (UTC)

I always learnt "Système Elégant Contre les AMéricains" though I also came across "Sans Experience contre les Americains" The Seventh Taylor (talk) 13:03, 29 September 2011 (UTC)

CVBS initalism

Regarding CVBS, the article states: "CVBS initialism, meaning "Composite Video, Blanking, and Sync". I've also come across Composite Video Broadcast Signal and ~ Baseband Signal. Even Composite Video, Burst, and Sync. Which is it? Is there an authoritive reference for this? The Seventh Taylor (talk) 13:06, 29 September 2011 (UTC)

According to the Dictionary of Electronics, Fourth Edition, Newnes, 1999, edited by S.W. Amos, R. S. Amos and G.W.A. Dummer, appendix , page 365, CVBS stands for "compositve video blanking and synch". Good enough for me. --Wtshymanski (talk) 14:45, 29 September 2011 (UTC)

Actually, CVBS has various definitions, Color Video Blanking Signal should be making the most sense - 'Composite' is all this combined and 'Blanking' and 'Sync' is somewhat the same thing. In German it's FBAS - Farb-Bild-Austast-Signal. I can also find

• Composite Video Baseband Signal
• Composite Video Burst Signal
• Composite Video, Burst and Sync
• Color, Video, Blanking, Synchronization
• Colour Video Blanking Sync
• Composite Video Broadcast Signal

in common use. All of these make sense and are from relevant sources. I'd guess we won't be able to trace this back in time to its definition. Any notion for adding at least the more popular definitions to the article? Zac67 (talk) 20:29, 21 October 2011 (UTC)

Cite it and write it. --Wtshymanski (talk) 21:52, 22 October 2011 (UTC)

RCA/BNC

Since the Yellow RCA connector is by far the most common connector, the term "yellow-plug video" has been suggested to help cut down on confusion between "composite" and "component" (which sound somewhat similar).

Samurai: what the hell does "commercial variations of video media" mean?

Why _IS_ composite referred to as RCA/BNC?

- 67.118.29.33 10:38, 31 Mar 2005 (UTC)

          Composite is referred to as RCA/BNC because those are the types of connecters used on the ends of the cable.
          An RCA plug is the common "yellow plug" video that is mentioned above.  BNC is an older style connecter that 
          attaches to coaxial cable.  BNC connectors can be found on old networking cards and all oscilliscopes.
                       mboylevt

BNC connectors are the professional choice and most professional video equipment will use BNCs for video input and output (composite, component, RGBHV, and in some cases even S-video); the RCA ("phono") connector is a poor connector in general, and regarded as particularly poor for video based on its electrical/shielding characteistics. BNC connectors are locking, mantain proper impedance and offer better shielding performance. Lincoln 69.17.11.103 17:35, 18 February 2007 (UTC)

The RCA plug has one major advantage over the BNC for consumer use which is why it is used - it's cheaper. 86.182.71.209 (talk) 17:05, 5 March 2011 (UTC)

Modulation channel

Every piece of consumer equipment I've used in the USA in the past 25 years modulated the signal onto channel 2 or 3 (not 3 or 4), what am i missing?

I have never, ever owned a piece of equipment that modulated the signal into channel 2. Always 3 or 4. Liquidtenmillion 00:51, 15 April 2006 (UTC)

I have never seen 2, but it is possible. Broadcast TV avoids using channels with no frequency gap between them. Some areas have 2 and 4, others 3. (There is a gap between 4 and 5, such that they can occur together.) Gah4 (talk) 19:01, 17 August 2017 (UTC)

Frequency

What is the normal frequency composite uses?

What is the typical and maximum equivalent resolution of video information carried by the CVBS format? 480 lines? Glueball (talk) 11:26, 13 May 2008 (UTC)

Unlike television channels, which are modulated onto an RF carrier, composite video is baseband. The signal ranges from 0Hz to about 4.5MHz. Television channels are about 6MHz wide, described variously as the lower end, the center, or the carrier frequency. US TV channel 2 is from 54 to 60MHz, for example, with the carrier at 55.25MHz.

Gah4 (talk) 09:18, 2 June 2008 (UTC)

Noise

The process of modulating RF with the original video signal, and then demodulating the original signal again in the TV, introduces several losses. This conversion also typically adds noise or interference to the signal as well. Other than noise, what are the losses? In theory, one can modulate an ideal carrier, and demodulate it again. The low signal levels of RF (it has to match what one could receive on an antenna) means noise is significant. (You can't escape thermal noise.) Generating a proper vestigial sideband signal is also tricky, but again, it can ideally be done without loss. Spectral errors aren't really losses, either. Gah4 (talk) 16:59, 28 May 2016 (UTC)

In theory, no problem but in the real world it is an additional two steps and the advice to avoid unnecessary modulation/demodulation when possible is sound. ~Kvng (talk) 17:03, 25 April 2021 (UTC)

Revert of new section about history of connectors

Nowhere on Wikipedia can you find any information about how the composite video connector relates to actual devices. It's almost solely relevant to consumer video equipment, but this page doesn't cover why it was added. You could maybe check Television, but that has no mention of it either. It's also many dozens of pages long, and mostly focuses on the "tele" part of television, which makes sense since almost all definitions of "television" have to do with the broadcast nature of it. A reader looking for information on the relationship between composite video and television would come here first.

It's impossible to cite any kind of "hard" reference for when composite video was added to TVs. It was not a deliberate decision made by a regulatory or standards body. Manufacturers just chose to do it when they saw the market drifting in the direction of home computers and VCRs. I could cite a book that says this, but that book in turn would be referencing something like Consumer Reports, if it referenced anything at all.

The fact that CR felt an entire half-page should be dedicated to explaining what this strange yellow jack was for, and that their previous years coverage absolutely left it out, is all the proof anyone could ask for that almost nobody had seen one of these before 1984. I don't think this revert made Wikipedia better, since the page still has a significant knowledge gap that has existed for decades and is virtually unfixable by this interpretation of the rules. — Preceding unsigned comment added by 97.113.158.191 (talk) 03:31, 16 July 2018 (UTC)

Claim: "It's almost solely relevant to consumer video equipment" That's very wrong. You must be completely unaware of the extent of industrial and business video equipment, most of which used comp video (usually on BNC connectors) long before those connectors started appearing on TVs. Heck, even a lot of broadcast/studio video gear, prior to HD, used composite video connections too. (Including "quad" VTRs and all of the associated switchers, monitors, etc., of that era.)

You can find history on the "RCA" connector at RCA connector.

Lots of things that would add arguably useful information to Wikipedia articles are precluded by the rules. Another good rule, btw, is to sign your talk page posts. Jeh (talk) 01:08, 18 July 2018 (UTC)

The material added was not good quality and not a good starting point for improvement because a competent history section would start with the professional applications that came first. I support Jeh's revert here. ~Kvng (talk) 14:13, 20 July 2018 (UTC)

For many years, lower cost television sets avoided using a power transformer, such that the whole chassis was directly connected to the power line. That makes it difficult to supply composite video inputs. Otherwise, it happened from the top down, as the extra cost was less significant for an already expensive set. The first one I bought was in 1986, a high-end JVC model (with three such inputs). Note also the addition of stereo audio, when TV sound was good enough to connect to an external stereo system, required those outputs, and, as above, electrical isolation. Video disks were also a source of higher quality home video that would have needed a connection system. About 1991, I bought a smaller JVC set, with (one) composite video input. Not a WP:RS, but that shouldn't be far from the timeline, as it went from high-end down. Gah4 (talk) 20:25, 20 July 2018 (UTC)

Indeed. "Transformerless" design, running all of the tube filaments in series to get up to the line voltage. Same thing with simple tube radios of the day. Depending on the orientation of the power plug the chassis - ie signal ground - had a 50/50 chance of being connected to AC "hot" vs neutral, and it was cheaper to just surround the set in plastic and make it not easy to touch anything metal that was in contact with the chassis. (The two-prong NEMA 1 plugs and sockets were not commonly polarized in those days.) This could have been addressed with a transformer for the comp video input, but a transformer that will nicely pass 4 MHz or so isn't cheap either. Pro gear used power transformers. Jeh (talk) 01:04, 21 July 2018 (UTC)

easily

Regarding the removal of Composite video can easily be directed to any broadcast channel simply by modulating the proper RF carrier wave with it. Actually, it is fine with me to remove it, but I thought I would discuss it anyway. The complication with easily is vestigial sideband modulation, otherwise it is the normally easy amplitude modulation. But for consumers, it is easy: just buy an RF modulator, which used to be available in the usual electronics stores. Maybe not quite as easy to find today, especially as more and more TV sets have video inputs. But yes, I don't see much reason to keep the statement in the article. Gah4 (talk) 21:35, 8 June 2019 (UTC)

The reason that RF modulators are so easy to build, is that there are ICs specifically designed to do it. Gah4 (talk) 22:07, 8 June 2019 (UTC)

References

modern day

The article indicates that Modern day devices with analog outputs have typically omitted the modulator option. I suppose, but a very popular modern day device is the HDTV converter, which most often does have RF output. But yes, I suspect that they are less common on DVD players and such than they used to be. Gah4 (talk) 22:40, 26 August 2019 (UTC)

I have removed the modern day claims. They were dated and uncited. ~Kvng (talk) 17:03, 25 April 2021 (UTC)