Separate Video, more commonly known as
S-Video and
Y/C, is often referred to by
JVC, usually referred to as JVC, is a Japanese international consumer and professional electronics corporation based in Yokohama, Japan which was founded in 1927...
(who introduced the DIN-connector pictured) as both an
S-VHSS-VHS is an improved version of the VHS standard for consumer-level analog recording videocassettes. It was introduced by JVC in Japan in April 1987 with the HR-S7000 VCR and certain overseas markets soon afterwards...
connector and as
Super Video. It is an
analog videoAnalog video is a video signal transferred by an analog signal. An analog color video signal contains luminance, brightness and chrominance of an analog television image...
transmission scheme, in which video information is encoded on two channels:
luma (luminance, intensity, "Y") and
chroma (colour, "C"). This separation is in contrast with lower-quality
composite videoComposite video is the format of an analog television signal before it is combined with a sound signal and modulated onto an RF carrier. In contrast to component video it contains all required video information, including colors in a single line-level signal...
, in which all video information is encoded on one channel, and higher-quality
component videoComponent video is a video signal that has been split into two or more component channels. In popular use, it refers to a type of component analog video information that is transmitted or stored as three separate signals...
, in which video information is encoded on three channels. S-Video carries standard definition video (typically at
480i480i is the shorthand name for a video mode, namely the US NTSC television system or digital television systems with the same characteristics. The i, which is sometimes uppercase, stands for interlaced, the 480 for a vertical frame resolution of 480 lines containing picture information; while NTSC...
or
576i576i is a standard-definition video mode used in PAL and SECAM countries. In digital applications it is usually referred to as "576i", in analogue contexts it is often quoted as "625 lines"...
resolution), but does not carry audio on the same cable.
The four-pin
mini-DIN connectorThe mini-DIN connectors are a family of multi-pin electrical connectors used in a variety of applications. Mini-DIN is similar to the larger, older DIN connector...
(shown at right) is the most common of several S-Video connector types. Other connector variants include seven-pin locking "dub" connectors used on many professional S-VHS machines, and dual "Y" and "C"
BNC connectorThe BNC connector ' is a common type of RF connector used for coaxial cable. It is used with radio, television, and other radio-frequency electronic equipment, test instruments, video signals, and was once a popular computer network connector. BNC connectors are made to match the characteristic...
s, often used for S-Video
patch panelA patch panel or patch bay is a panel, typically rackmounted, that houses cable connections. One typically shorter patch cable will plug into the front side, whereas the back holds the connection of a much longer and more permanent cable...
s. Early Y/C video monitors often used phono (
RCA connectorAn RCA connector, sometimes called a phono connector or cinch connector, is a type of electrical connector commonly used to carry audio and video signals...
) that were switchable between Y/C and composite video input. Though the connectors are different, the Y/C signals for all types are compatible.
Overview
The
luminanceIn video, luma, sometimes called luminance, represents the brightness in an image . Luma is typically paired with chrominance. Luma represents the achromatic image without any color, while the chroma components represent the color information...
(Y; grey-scale) signal and chrominance (C; colour) information are carried on separate, synchronised signal and ground pairs.
The luminance signal carries horizontal and vertical
synchSynch or sync may refer to:*DIN sync, a standard interface for electronic music instruments*File synchronization or syncing, to synchronize directories or files on computers*Ford Sync, an in-car communications and entertainment system...
pulses in the same way as a
composite videoComposite video is the format of an analog television signal before it is combined with a sound signal and modulated onto an RF carrier. In contrast to component video it contains all required video information, including colors in a single line-level signal...
signal, but S-Video luminance information can have a higher bandwidth than in composite video, which must devote some of its bandwidth to the chrominance information (beginning at roughly 3 Megahertz, depending on the encoding standard used). Both luminance and chrominance information in composite video therefore have to be
low-pass filterA low-pass filter is an electronic filter that passes low-frequency signals but attenuates signals with frequencies higher than the cutoff frequency. The actual amount of attenuation for each frequency varies from filter to filter. It is sometimes called a high-cut filter, or treble cut filter...
ed else crosstalk between high-
frequencyFrequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
luminance information and the colour
subcarrierA subcarrier is a separate analog or digital signal carried on a main radio transmission, which carries extra information such as voice or data. More technically, it is an already-modulated signal, which is then modulated into another signal of higher frequency and bandwidth...
will lead to unwanted
video artifactsA digital artifact is any undesired alteration in data introduced in a digital process by an involved technique and/or technology.-Possible causes:...
patterning when viewed. As S-Video maintains the two as separate signals, but still encodes two colour-difference signals into one chroma subcarrier, such detrimental low-pass filtering for luminance is unnecessary, although the chrominance signal still has limited bandwidth, and the colour crosstalk problem is subdued. The infamous
dot crawlDot crawl is the popular name for a visual defect of color analog video standards when signals are transmitted as composite video, as in terrestrial broadcast television. It consists of animated checkerboard patterns which appear along vertical color transitions...
is eliminated. This means that S-Video leaves more information from the original video intact and offers an improved image reproduction compared with composite video.
Other strengths and weaknesses
S-Video, with its two signals for video, is a compromise in terms of quality and convenience between
composite videoComposite video is the format of an analog television signal before it is combined with a sound signal and modulated onto an RF carrier. In contrast to component video it contains all required video information, including colors in a single line-level signal...
with one, and three-wire (or more)
component videoComponent video is a video signal that has been split into two or more component channels. In popular use, it refers to a type of component analog video information that is transmitted or stored as three separate signals...
schemes. Using two video lines will, for example, use two inputs of video processing Integrated Circuits where two composite video inputs could have been accommodated, e.g. in the TVP5154A.
Compared with
component videoComponent video is a video signal that has been split into two or more component channels. In popular use, it refers to a type of component analog video information that is transmitted or stored as three separate signals...
schemes where separate Red, Green and Blue (or luminance and two colour-difference signals) are given their own cables, S-Video is:
- poorer quality, because the colour information encoding (with a subcarrier
A subcarrier is a separate analog or digital signal carried on a main radio transmission, which carries extra information such as voice or data. More technically, it is an already-modulated signal, which is then modulated into another signal of higher frequency and bandwidth...
frequency of perhaps 3.57 to 4.43 Megahertz, depending on standard) limits the maximum theoretical chrominance bandwidth possible, although the signal source may have its own limitations. [comment mention 4:2:2 etc?]
- Carrying the colour information as one signal means that the colour has to be encoded in some way, and as such, NTSC
NTSC, named for the National Television System Committee, is the analog television system that is used in most of North America, most of South America , Burma, South Korea, Taiwan, Japan, the Philippines, and some Pacific island nations and territories .Most countries using the NTSC standard, as...
, PALPAL, short for Phase Alternating Line, is an analogue television colour encoding system used in broadcast television systems in many countries. Other common analogue television systems are NTSC and SECAM. This page primarily discusses the PAL colour encoding system...
, and SECAMSECAM, also written SÉCAM , is an analog color television system first used in France....
signals are all decidedly different through S-Video. Thus, for full compatibility, the connected devices not only have to be S-Video compatible, but also compatible in colour encoding. In addition, S-Video suffers from reduced colour resolution. NTSC S-Video colour resolution is typically 120 lines horizontal (approximately 160 pixels edge-to-edge), versus 250 lines horizontal for the Rec. 601-encoded signal of a DVD, or 30 lines horizontal for standard VCRs.
Compared with
Digital videoDigital video is a type of digital recording system that works by using a digital rather than an analog video signal.The terms camera, video camera, and camcorder are used interchangeably in this article.- History :...
systems, S-Video:
- requires less processing to feed analog televisions but more complex processing (and hence quality loss) to interact with digital systems, including computer storage and processing, as well as most modern televisions.
- Depth of colour depends in S-Video, and other analog video
Analog video is a video signal transferred by an analog signal. An analog color video signal contains luminance, brightness and chrominance of an analog television image...
systems, on the Signal-to-noise ratioSignal-to-noise ratio is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. It is defined as the ratio of signal power to the noise power. A ratio higher than 1:1 indicates more signal than noise...
, but in digital systems it depends on the number of bits allocated (e.g. 2 bits to each colour-difference signal in 8-bit ITU-R BT.656ITU-R Recommendation BT.656, sometimes also called ITU656, describes a simple digital video protocol for streaming uncompressed PAL or NTSC Standard Definition TV signals...
may mean S-Video has more realistic colours, even if the resolution and noise performance is worse than the digital system).
When used for connecting a video source to a video display that supports both 4:3 and 16:9 display formats, the PAL television standard provides for signalling pulses that will automatically switch the display from one format to the other. The S-Video connection transparently supports this operation. The S-Video connection also has general provision for widescreen signalling through a DC offset applied to the chrominance signal; however, this is a more recent development that is not widely supported.
History
In 1987,
JVC, usually referred to as JVC, is a Japanese international consumer and professional electronics corporation based in Yokohama, Japan which was founded in 1927...
's release of
S-VHSS-VHS is an improved version of the VHS standard for consumer-level analog recording videocassettes. It was introduced by JVC in Japan in April 1987 with the HR-S7000 VCR and certain overseas markets soon afterwards...
introduced the S-Video cable standard. With these cables, the S-VHS video cassette systems play with their full potential, completing the improved definition and resolution into a compatible TV. Due to low market penetration of television sets and video devices equipped with S-Video ports, the format failed to become a mainstream image standard and remained in the niche high-end
home cinemaHome cinema, also commonly called home theater, are home entertainment set-ups that seek to reproduce a movie theater experience and mood with the help of video and audio equipment in a private home....
market.
In the late 1990s, big-screen television sets began shipping with S-Video option in input ports, thus increasing the number of supportable electronic devices such as
DVD playerA DVD player is a device that plays discs produced under both the DVD-Video and DVD-Audio technical standards, two different and incompatible standards. These devices were invented in 1997 and continue to thrive...
s,
satellite receiverAn integrated receiver/decoder is an electronic device used to pick-up a radio-frequency signal and convert digital information transmitted in it.-Consumer IRDs:...
s, and
video game consoleA video game console is an interactive entertainment computer or customized computer system that produces a video display signal which can be used with a display device to display a video game...
s. The format gained some popularity as a better alternative to composite video inputs. S-Video was also adopted in the graphics card market in the early 2000s to provide a video output from computers to TVs.
The introduction of component video, offering a better image and
backward compatibilityIn the context of telecommunications and computing, a device or technology is said to be backward or downward compatible if it can work with input generated by an older device...
, replaced S-Video as the default alternative to the composite video on many high-end cards. Laptops commonly included an S-Video output, but since the mid-2000s, this function on new models has been replaced by
DisplayPortDisplayPort is a digital display interface standard produced by the Video Electronics Standards Association . The specification defines a royalty-free digital interconnect for audio and video. The interface is primarily used to connect a video source to a display device such as a computer monitor...
or
HDMIHDMI is a compact audio/video interface for transmitting uncompressed digital data. It is a digital alternative to consumer analog standards, such as radio frequency coaxial cable, composite video, S-Video, SCART, component video, D-Terminal, or VGA...
outputs.
Etymologically, the word
S-Video has several denotations:
Super Video (complementing
Super VHS),
Separated Video, and
S-VHS cable.
Connector and Cable
An S-Video signal is generally connected using a cable with four-pin mini-DIN connectors. Apart from the impedance requirement, these cables are equivalent to regular mini-DIN cables (like Apple's
ADBApple Desktop Bus is an obsolete bit-serial computer bus connecting low-speed devices to computers. Used primarily on the Macintosh platform, ADB equipment is still available but not supported by most Apple hardware manufactured since 1999....
). Apple-type cables can be used for S-Video transfer if no other cable is available, but picture quality may not be as good. Due to the wide use of S-Video connections for DVD players, S-Video cables are fairly inexpensive compared to component or digital connector cables.
The mini-DIN pins, being weak, sometimes bend. This can result in the loss of colour or other corruption (or loss) in the signal. A bent pin can be forced back into shape, but this carries the risk of the pin breaking off.
The cable should be made up with two
twisted pairTwisted pair cabling is a type of wiring in which two conductors are twisted together for the purposes of canceling out electromagnetic interference from external sources; for instance, electromagnetic radiation from unshielded twisted pair cables, and crosstalk between neighboring pairs...
s (one for the luminance (pins 3/1) and one for the chrominance (pins 4/2)), with an overall screen connecting the shells. Preferably, the pitch of the twists should be different, as in a Cat 5 LAN cable. However, Cat 5 cable has solid core wires and, generally, no overall screen, so it is not suitable for this application. Alternatively, two separately screened cables with an overall screen may be used. This will significantly reduce crosstalk between each signal pair. Use of ordinary or unscreened cables causes impedance mismatches, which will degrade the picture.
Before the mini-DIN plug became standard, S-Video signals were often carried through different types of connectors. For example, the
Commodore 64The Commodore 64 is an 8-bit home computer introduced by Commodore International in January 1982.Volume production started in the spring of 1982, with machines being released on to the market in August at a price of US$595...
home computerHome computers were a class of microcomputers entering the market in 1977, and becoming increasingly common during the 1980s. They were marketed to consumers as affordable and accessible computers that, for the first time, were intended for the use of a single nontechnical user...
of the 1980s, one of the first widely available devices to feature an S-Video output, used an eight-pin connector similar to the
DIN connectorA DIN connector is a connector that was originally standardized by the , the German national standards organization. There are DIN standards for a large number of different connectors, therefore the term "DIN connector" alone does not unambiguously identify any particular type of connector unless...
on the computer end and a pair of phono plugs on the monitor end. (Also available via third-party vendors was an eight-pin DIN-to-4-pin mini-DIN to connect the Commodore directly to a television.) The S-Video connector is the most common video-out connector on older laptop computers; however, many devices with S-Video outputs also have composite outputs.
The Atari 800 home computer featured S-Video outputs in 1979 (three years before the Commodore 64), via a five-pin DIN plug.
Both S-Video and audio (mono or stereo) signals can be transferred through
SCARTSCART is a French-originated standard and associated 21-pin connector for connecting audio-visual equipment together...
connections as well. However, it is not part of the original SCART standard, so many SCART-compatible devices do not support it for this reason. Also, S-Video and RGB are mutually exclusive through SCART, due to S-Video using some of the pins allocated for RGB. Most SCART-equipped televisions and VCRs (and almost all of the older ones) do not support S-Video, resulting in a monochrome picture if such a connection is attempted, as only the luminance signal portion is usable. A monochrome picture could also be a sign of incompatible colour encoding: for example, NTSC material viewed through a PAL-only device.
Another incompatibility (due to S-Video not being part of the original SCART standard) is when connecting a SCART output device such as a cable TV box to a TV with a mini-DIN S-Video input. In many cases when this connection is made, the result will be a predominantly black-and-white picture, with most of the colour (chrominance signal) washed out. An example of this is when connecting the SCART output of a FOXTEL Digital Box (Australia) to a mini-DIN S-Video input of a TV. An impedance mismatch between the SCART and mini-DIN interfaces causes the signal levels to be reduced at the TV end, resulting in a poor picture. This problem can be overcome by terminating the chrominance line of the SCART plug with a 75-ohm resistor, correcting the mismatch. Many high-end sets do support this connection, however (without the termination), due to their inputs having a larger dynamic range.
At least some Fujitsu laptops (S-7020, S-7110) use so-called mini S-Video connector for TV-Out. This mini S-Video connector is actually a 3.5mm TRS connector where tip and ring carry Y/C, both using the sleeve as ground. Such a mini S-Video is rare, and it is very difficult to obtain a proprietary cable for it.
7-pin mini-DIN
This is a non standard 7-pin mini-DIN connectors (this variant is called "7P"). These are used on computer equipment (PCs). A 7-pin socket accepts and is pin compatible with standard 4-pin S-Video plug. The three extra sockets may be used to supply
composite (CVBS)Composite video is the format of an analog television signal before it is combined with a sound signal and modulated onto an RF carrier. In contrast to component video it contains all required video information, including colors in a single line-level signal...
or an RGB or YPbPr video signal, or an
I²CI²C is a multi-master serial single-ended computer bus invented by Philips that is used to attach low-speed peripherals to a motherboard, embedded system, cellphone, or other electronic device. Since the mid 1990s, several competitors I²C ("i-squared cee" or "i-two cee"; Inter-Integrated Circuit;...
interface. The
pin outIn electronics, a pinout is a cross-reference between the contacts, or pins, of an electrical connector or electronic component, and their functions.- Purpose :...
usage varies between manufacturers. In some implementations, the remaining pin needs to be grounded to enable the composite output (or disable the S-Video output on some of those implementations).
9-pin Video In/Video Out
These are used on graphics systems that feature the ability to input video as well as output it. Again, there is no standardisation between manufacturers as to which pin does what (also given that there 2 known variants of the connector in use). As can be seen from the diagram above, although the S-Video signals are available on the corresponding pins, neither variant of the connector will accept an unmodified 4-pin S-Video plug, though they can be made to fit by removing the key from the plug. In this latter case, it becomes all too easy to misalign the plug when inserting it with consequent damage to the small pins.
Usage
In many European Union countries, S-Video is less common because of the dominance of SCART, which allows RGB quality and is usually fitted to every TV. It is not usual to find S-Video outputs on equipment such as DVD players, although the player may output S-Video over SCART, but the TV may not be compatible with S-Video wired this way, and so would just show a monochrome image. In this case it is sometimes possible to modify the SCART adapter cable to make it work. Games consoles usually do not output S-Video, due to the dominance of SCART with its better RGB quality. However, in the US and other non-SCART countries, S-Video is provided but no RGB. The
Nintendo 64The , often referred to as N64, was Nintendo′s third home video game console for the international market. Named for its 64-bit CPU, it was released in June 1996 in Japan, September 1996 in North America, March 1997 in Europe and Australia, September 1997 in France and December 1997 in Brazil...
was an exception - NTSC models could output S-Video, but only with modification could they output RGB. PAL Nintendo 64 models could output S-Video but not RGB despite, that being the easiest way to connect if done via SCART.
There is, however, a German company that is able to modify PAL N64's to output true RGB although this service is rather expensive compared to the way you can make an NTSC model output RGB.
Converting S-Video signals
- Simple mixing (addition of voltages) after appropriate low-pass filter
A low-pass filter is an electronic filter that passes low-frequency signals but attenuates signals with frequencies higher than the cutoff frequency. The actual amount of attenuation for each frequency varies from filter to filter. It is sometimes called a high-cut filter, or treble cut filter...
ing is required to convert S-Video to composite videoComposite video is the format of an analog television signal before it is combined with a sound signal and modulated onto an RF carrier. In contrast to component video it contains all required video information, including colors in a single line-level signal...
. Conversion to or from any other standard requires more sophisticated circuitry.
- Encoding the R, G, and B analog components of a video signal into S-Video luminance and chrominance, or composite video, requires some analog processing, such as that provided by the AD723 integrated circuit
An integrated circuit or monolithic integrated circuit is an electronic circuit manufactured by the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material...
(chip).
- Converting S-Video to or from digital video signals, depending on the digital standard involved, requires more processing - such as the CS4954 NTSC/PAL Digital Video Encoder when converting from 27 MHz 8-bit YUV, 8-bit YCbCr, or ITU R.BT656.
See also
- Audio and video connector
Audio connectors and video connectors are electrical connectors for carrying audio signal and video signal, of either analog or digital format. Analog A/V connectors often use Shielded cable to inhibit radio frequency interference and noise.- Audio only :Audio connectors are electrical...
- RF connector
A coaxial RF connector is an electrical connector designed to work at radio frequencies in the multi-megahertz range.RF connectors are typically used with coaxial cables and are designed to maintain the shielding that the coaxial design offers. Better models also minimize the change in transmission...
- Composite monitor
A composite monitor is any analog video display that receives input in the form of an analog composite video signal through a single cable — in contrast to multiple-cable or multiple-wire video sources such as VGA cable...
- List of video connectors
- Video In Video Out (VIVO)
Video In Video Out, usually seen as the acronym VIVO , is a graphics port which enables some video cards to have bidirectional analog video transfer through a mini-DIN connector, usually of the 9-pin variety, and a specialised splitter cable .VIVO is found on high-end ATI and NVIDIA...