S-Video

S-Video (also known as Separate Video, Y / C ) refers to the device sending the (luminance ) - and chrominance (color ) information on appropriately designed cable and connectors. It allows, especially when used in low-cost devices, better quality than composite video signals, but does not reach the quality of RGB signals or component video.

S-Video is often wrongly equated with the Video Recording Format S-VHS ( Super Video Home System).

Description

The luminance signal and the modulated color subcarrier are transmitted over two separate Signal-/Masseleitungspaare. The luminance signal (Y) is basically a black and white television signal (BAS). The color signal (C) is quadrature -modulated in the usual way, but not mixed with the luminance signal as composite / composite video but transmitted via a second connection conductor.

Unlike composite video no chrominance filter in the receiver is in S- video, therefore, necessary that again would have to separate from the luminance signal, the color signal. This not only cross- luminance and cross-color interference is avoided, but also broader-band video signals possible. Due to the separately transmitted chrominance allows S-Video Composite Video over a higher bandwidth for the luminance information. Due to the gain in the horizontal resolution ( in one line each ), details more visible.

An increase in the transmission bandwidth of the color signal is possible, but is rarely used in practice.

Video signals are digitally processed to transfer or at the latest for display. As a PAL video has 576 information-carrying lines, already resulting in an aspect ratio of 4:3 in the case of square pixel resolution of 768 × 576 pixels. In order to resolve two adjacent points would have the brightness signal bandwidth of 14.75 MHz have what should be available through high-quality Y / C video conversion for S- Video outputs of high resolution video cameras or cameras easily.

Technical details

S- video is not a video format. It is it rather the corresponding baseband analog television standard basis. Depending on the CCIR transmission standard document brightness and color signal other frequencies.

For the common in Germany PAL color signal as with CVBS / Composite video is transmitted at 4.43361875 MHz. The range of Farbartmodulation is nominally about ± 1.3 MHz.

The luminance signal is due to the non-embedded color signal and frequency components higher than that in CVBS / Composite Video sufficient 3MHz included with S-Video.

Composite Video Adapter

S-Video should in order to benefit from the advantages of this type of connection can only be used between S-Video capable devices. However, it may happen in the home in particular that you want to feed a composite video device with S- video ( eg notebook on TV).

The S -Video signal can be achieved by filtering the luminance signal (Band lock in color with the color carrier signal does justice to bandwidth) and an additive link to the chrominance signal into a Composite / CVBS signal return lead.

Simple S- Video to composite adapter only use the luminance of the S- video port. Since both video signals are transmitted at each 75 ohms, which is a problem ( when using a 75-ohm cable ). At the composite output of such an adapter but then is only a S / W signal. Is the luminance signal band-limited not appropriately may lead to chrominance artifacts due to lack of filter.

A very simple circuit that can add the amount of color, associated luminance (Y) and chrominance signal (C ) through a 470 pF capacitor, and picks up a " composite " signal to the Y pin. This gives a sufficiently good color image ( criticism are the transmission and reflection properties esp. the supply of Chrominanzeingangs ). Again, missing the really necessary filtering of the luminance signal. This circuit can not be used for the reverse path (from Composite to S-Video ), plus active components are required.

Plug

Today, S-Video signals are generally 4 -pin mini - DIN connector (also called Hosidenstecker ) transferred with a terminating resistor of 75 ohms. The pins in the connector bend easily, so infecting requires caution. If a pin is bent, causing the loss of color, or corrupts the signal leads to its complete loss.

Sometimes mini- DIN connector with 4 poles are used for S-Video. In this case, located on the pins that are in the usual positions of the 4 -pin connector, also the usual S-video signals, while other pins eg Composite, RGB and / or Component signals contain. Such solutions were found intermittently on PC graphics cards, since there also a number of TV sockets could not be mounted because of the lack of space on the rear panel next to two PC monitor connections. These solutions were vendor specific and required the use of a supplied or separately by the manufacturer adapters to cable when other waveforms should be taken as S-Video. For use as an S -Video jack on the other hand standard cable could be used, the connector simply not contacted all the pins of the socket.

Marriage mini-DIN standard was, you used different plug shapes for S-Video. For example, was the home computer Commodore 64 ( 1980 ), could pose as one of the first mass devices S-Video signals, an 8 -pin DIN connector on the computer and a pair of RCA connectors used on the monitor.

Today, the S- video signal can also be transmitted via SCART connector. However, the input in question must be explicitly support S- video because it is not part of the SCART standards. In addition, the simultaneous support of RGB and S-video signals via a single SCART socket circuitry is hardly possible, since this too few lines are present. With most TVs with two SCART sockets both can be supplied with composite video, but only one of the two processed RGB or S-Video. If only one SCART socket on the device is present, this almost always takes composite and RGB, but not always S-Video. Unlike the switch between composite and RGB signals, which (eg TV ) can be signaled automatically SCART from the sending device (eg DVD player ) via a purpose reserved line to the receiving device, the switching between composite and S must video signal are almost always carried out at the receiving device by hand, as this offers no SCART signal line.

Use

S-Video is commonly used in home DVD players and VCRs. Even with professional technology, as well as in computer video cards, it sometimes is used in the computer field, however, it has now been largely suppressed by newer digital connection types such as DVI, HDMI and DisplayPort. In Europe, S-Video was formerly not as common, because there usually RGB signals via SCART sockets were used. In the U.S. and in Japan, where SCART sockets are virtually unknown, was and is S-Video, however, the most widely used type of connection for high-quality television and video components. By now, S- video in Europe, due to the high proportion of foreign brands in the field of consumer electronics, to the usual standards.

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