Index


Video Connectors Page

    Connector standards

    Connectors, Resolution, Digital, Analog, VGA, DVI-- there seems to be a never-ending stream of terminology and concepts used in the A/V industry. In this page you will see an overview of concepts needed to understand most often used signal types and connectors in a video system.There are very many different video connectors in use in consumer and professional video systems.Traditionally, televisions have only needed one type of input to accept the single coaxial antenna socket. Besides that there are many different video signal transmission formats like composite video, S-video (Y/C), RGB and component video. Depending the situation any one of the following video signals could be connected using many different connectors. To make a good video connection between two equipments you must always make sure that the video formats match and you can get or make a suitable cable between whatever connectors the video equipments have.

      Most common connectors for composite video and S-video connections

      Composite video is transporeted using one coaxial cable connector.The most commonly used connectors for composite video are RCA connector and BNC connector. The center pin carries the signal and the outer shield connects the cable shield.

      Sometimes you might ask what is the maximum length of the S-video or composite video connection. This really depends on the quality of the cable. Usually almost any shielded wire can transfer composite video for few meters. A good quality 75 ohm coaxial cable (RG59 or RG6) can transfer compotite video signal for few tens of meters without noticable loss in picture quality. And you can go with the same cable usually up to 100 meters if you allow some image quality loss. If you use a lower quality cable, you will see picture quality loss at shorter distances. This applies also to most other similar video signals.

      S-video signal (also called Y/C-signal) splits the video signal to two parts (luminance and color) which are transported using two different coaxial cables. The standard conector used for S-video is 4-pin mini-din connector. Some computer cards use proprietary connectors for S-video (for example 7-pin mini-din). S-video gives you generally better picture quality than composite video, especially on the sharp computer generated images. Because the S-video interface keeps the luminance and color information separate, there is no cross-intergfrence between them as you sometimes see on the composite video signal (looks like strange noise on the edges of strong color/intensity changes).

      Standard s-video cable will usually work well up to 25 feet, but you will probably experience signal loss and picture degradation as you go beyond 25 feet (although you may not notice it). Longer lengths up to 100 feet (around 30 meters) require a better quality, heavier grade s-video cable. Lengths beyond 100 feet (around 30 meters) require a high quality cable or a dual cable solution (where two separate cables are used which rejoin at each end into an s-video connector. Two RG6 cables with BNC connectors at each end and our s-video/(2) BNC adapter is often used reliably up to 200 feet (around 60 meters).

      The signal quality difference between composite video and S-video can be from very dramatic to not very big depending on the signal and equipment quality. A very good quality composite video signal that leaves from one good quality professional video equipment to another professional video equipment can be of very high quality, just very slightly lower in quality than S-video. On the other hand the quality of composite video generating circuits and the composite video signal processing electronics inside many consumer electronics devices are usually not very good, and this causes that all kinds of internsity/color interference problems become easily visible on the image. In this kind of case the quality difference between S-video and composite video can be huge, S-video being very much better looking than composite video.

      Antenna connectors

      TV antenna signals are carried using coaxial cable. The typical coaxial cable connector used in USA for TV antenna signals is F-connector. In Europe antenna signal connections in devices are IEC antenna connectors (also called Euro TV connector). Those are the most commonly used antenna connectors, which are used in almost all TVs and VCRs. Some smal TVs use 3.5 mm mini-phone jack as antenna connector. The mini-phone jack is likely the same as the F-connector now commonly used for RF (antenna) input, so you can adapt those signal with hust connector adapter. Some very old equipment can have also other connectors like two pin connector used for flat 300 ohm line cable connection.

      Information on SCART connector

      In Europe, the external connections to TVs, set-top boxes, VCRs and other video peripherals are provided by a SCART, or Peritel, connector. Its pin-out is specified in EN50049. Depending on the SCART connector's use (TV SCART, AUX SCART, or VCR SCART) the connector is an input, an output, or both. The SCART (Syndicat des Constructeurs d'Appareils Radior?cepteurs et T?l?viseurs) is a twenty one pin connector plug developed by the European community and found on the back of most European televisions and video players. The connector is also known as Pertitel connector or Euroconnector. The formal description of SCART connector is given in the CENELEC EN 50 049-1:1989 standard and in the IEC 933-1 standards. SCART connector is used in most of the consumer video equipments like VCRs, TVs and DVD players to hand the audio and video connections all using some connector. SCART connector supports stereo audio, composite video, S-video, RGB and some control signals. SCART connector can use to carry many signal formats, but it can't carry all of them at the same time. Note that not all SCART connections in all equipment are equivalent, connectors on other equipments might support more signal format than others. Originally standardized signal format for SCART connnector were composite video and RGB.The addition of S-VHS complicated this interface by requiring the RED and Cvbs pins (15 and 20) to be shared with the Chroma (C) and Luma (Y) pins.Different pin-configurations exist. Which confirations are available depends on the video device used.Composite video and audio are practically always supported, but there are lots of equipments which do not support RGB or S-video. For example some TVs support RGB on one SCART and S-video on other SCART (in addition to standard composite video format).The supported RGB signal format is RGBS (R, G, B and composite sync).In most cases, specialized ICs are used for the SCART interface because of the complicated switching required. Because SCART supports many signal formats, there must be a way tocontrol what is used.Selection of the input and output signal is then usually controlled in combination with the control pins in SCART connector and via setup menu of the machine. SCART has control signals for example to switch between composite video and S-video. I addition to this there is a signal foraspect ratio switching from wide-screen to normal. There is also a control signal for the TV to switch automatically to view picture from SCART connector. Usually the switching between S-video and other formats need an user setting on TV menu or input selector button (some TVs have S-video auto-detect for this).S-video connection with SCART connector seems to cause lots of problems to many people. When working with SCART and S-video, remebr that S-video works on SCART interface only with devices that support S-video. Many SCART implementations do not support S-video, because the original SCART specification did not support it (it was added later on to the specifications as extra option). The most common problems that users generally face with SCART connector is that they get black & white picture when they connect S-video to their TV SCART connector. The reason for this is usually that the TV is not capable ofhandlign S-video or is not set to handle S-video-signal from SCART. TV doesn't know by itself if a S-video or standard CVBS input is used. Usually the user needs to inform the TV what signal format is used. If the TV thinks that a normal CVBS inputis used, then the picture will be black-and-white because theluminance signal doesn't contain the color information but is the same"format" as CVBS. Most tv's doesn't have automatic detection of whichof the two is used so you usually have to tell it that. (like pressingthe A/V button twice etc.) The same thing happens if you connect aCVBS source and put the TV in S-video mode. In this case your SCART interface does not support S-video and you want picture with colors, the solution is to use composite video interface instead (it is supported by practically all SCART implementations). S-video can be converted to composite video with a commercial converter orwith a simple conversion circuit.If your TV has SCART connector or not depends mostly where you live.Practically all TVs madefor European market (no matter what is the brand) have SCARTconnector in them. SCART is European standard AV connector,so consumer expect to have this.In countried outside Europe this connector is less common.For example in USA markets this connector is very rare.There is no technical reason why NTSC TV could not havea SCART connector. When buying Scart interconnects remember that they're not created equal. Some of the cheaper fully wired cables employ an overall shield, instead of screening each conductor separately. Over the length of the cable, the various signals may interfere with each other. The most obvious problem is an audible buzz, caused by the video signal leaching onto the audio wires. You can also sometimes see ghosing video images as video signal bleed form one wire to another. Inexpensive cables have also often cheaply made Scart plugs, that may tarnish with age, leading to intermittent connection. When buying SCART cables, look for a good quality "fully connected" and "separately shielded signals" wire. Those are somewhat more expensive than cheapest cable, but you can get this kind of cable at reasonable prices if you shop around somewhat. Good quality cable gives you good quality audio and video without quality loss that poor quality cables will give you. We?ve yet to find any professional user who actually likes the Scart design of connector. As this curiously designed, and generally exceedingly flimsy, connector is a product of the consumer market.

      Component video

      Component Video splits the video signal up into three separate components (Y/Pb/Pr) for preserving high resolution and accurate color rendition. Component video (YUV and it's derivatives like Y/Pr/Pb) have grown and faded in popularity several times. Nowdays the use of them seems to be growing in USA where it has become the highest quality commonly available interface to link home studiuo equipment (DVD players, video projectors, projection TVs, HDTV equipment, etc.). Component video has been known the widely supported consumer video interface that supports "progressive" or "non-interlaced" video signals as well as HDTV signals.

      When an RGB source is encoded into composite or S-Video, YUV is the intermediate signal used in the processing. YUV still has a limitation on the color bandwidth but it is far superior to the encoded composite or S-Video signals. Luminance (Y component) is full bandwidth.

      Other variations have been know as Y/R-Y/B-Y, M-II and the more recent consumer standard of Y/Pb/Pr. Y/Pb/Pr may catch on as an industry standard since a significant number of new chips support it. All three derivatives are very similar with only some level and other minor differences.

      Transporting component video formats described above takes three high quality cables (75 ohm coaxial cable). Y/Pb/Pr is widely used in new cosumer video devices in USA. It is found nowadays in such devices like DVD players, video projectorsand high-end TVs (including HDTV receivers).Most consumer devices use three RCA connectors to connect Y/Pb/Pr signal. Those three RCA cables are typically marked with colors red, green and blue. The typical color codes for this connector set are:

      • Green = Y (luminance)
      • Red = Pr (R-Y)
      • Blue = Pb (B-Y)

      In some video projectors a DB15HV connector ("VGA connector") is usedto carry this signal format. In those applications the componentvideo signals are connected to those pins which normally carry the RGB signals. For interconnecting to such system sny standard HD15 to 5bnc/phono would do the job. You'd just use the Green for Y, Red for Pr and Blue for Pb (this is the most commonly used configuration).


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