Introduction
Composite video and S-video are widely different from one another. An amateur may have little to no knowledge about these two different types of signals and may not know about the differences; thus, it is important to first study what composite and S-video are.
The composite video takes the form of an analog video signal that is then combined with an audio signal and modulated with an RF carrier. It is a mixed signal combined with synchronisation pulses from three different sources (Y, U, and V). Y represents lightness; U and V carry hue and saturation, which together make up chroma. Therefore, U and V together carry the information for the color signal. Composite video is also often referred to as CVBS, which stands for Color, Video, Blank, and Sync.
S-video is called "separate video" and is sometimes incorrectly referred to as "super video". This is also an analog video signal that carries information with two different symbols: chroma, meaning color, and luma, meaning brightness. It transmits defined video over a cable and does not combine it with an audio signal. S-video and composite videos differ in many ways.
Composite Video vs. S-Video
Composite video uses a single RCA connector to transmit the entire video signal, which includes luma (brightness) and chromaticity (color) information. Signals are combined into a single channel and sent via RCA connectors. This results in a lower-quality video signal compared to S-Video and other connection types.
The S-video, on the other hand, splits luminance and chromaticity data into two separate signals transmitted over two RCA connectors. This results in a higher-quality video signal than composite video. However, S-Video is still an analog signal with limitations in resolution and clarity.
Difference Between Composite Video and S- Video in Tabular Form
| Properties | Composite video | S- video |
| Definition | Composite video is the form of an analogue television (picture only) signal before it is amalgamated with a sound signal and modulated onto an RF carrier. | Separate Video, more commonly known as S-Video, also called Y/C, is an analogue video signal that imports video data as two separate signals: Luma (luminance) and chroma (colour). It is also sometimes incorrectly known as super video |
| Connector | RCA connector, 1/8 inch Jack plug, etc. | Mini- DIN connector |
| Pins | 1 plus shield | 4 or 7 |
| Picture Signals | Up to 576i (~768x576) | Carried through 2 separate signals |
| Picture Quality | Average/ Good | Excellent |
| Demand | Have low consumer demand due to average picture quality | Have high consumer demand due to excellent picture quality |
| Low Pass Filter | Required | Not required. |
What is Composite Video?
Composite video is a type of analog video that typically carries 525 or 625 lines per channel, as opposed to premium S-video (two channels) and premium component video (three or more channels).
Yellow RCA connectors are mostly used for video mixing, and audio is carried via additional left and right RCA connectors. Other connection types can be used in professional installations or for devices that are too small for RCA connectors, such as digital cameras.
Composite Video is also known as Composite Video Baseband Signal for Color, Video, Dimming, and Synchronization, CVBS, or SD Video for short, because of the standard-definition TV signal it carries.
There are three different types of mixed signals, which correspond to the analogue color systems used (NTSC, PAL, and SECAM), but pure monochrome signals are also available.
Modulators
Some devices, such as video cassette recorders (VCRs), video game consoles, and home computers, provide composite video output. This can be converted to RF using an RF modulator by creating the appropriate carrier (usually channel 3 or 4 in North America or channel 36 in Europe). Sometimes a modulator has a product (like a video game console, VCR, Atari, Commodore 64, or TRS-80 CoCo home computer), an external device used by the computer (TI-99/4A), or a separate power source.
Due to the transition to digital TV, most TVs do not have an analog TV tuner and cannot receive signals from analog modulators. However, video composites are commercially available for devices that convert them to channel 3/4 output as well as for devices that convert formats such as VGA to video.
Connectors and Cables
In-home applications, composite signals are often connected using RCA connectors (usually yellow). It usually has red and white connectors for the left and right audio channels. BNC connectors and better coaxial cables are often used in professional TV studios and post-production applications. BNC connectors were also used for video connections on the first home video recorders; usually, they had RCA connectors or 5-pin DIN connectors for audio. The BNC connector is behind the PL-259 connector on first-generation VCRs.
The video line impedance is 75 ohms and has low capacitance. Values range from 52 pF/m for HDPE foamed dielectric precision video cables to 69 pF/m for solid PE dielectric cables.
What is S-video?
S-Video (also called Separate Video, Y/C, and erroneously Super Video) is an analog video signal format that transmits standard video definition, usually 525 or 625 lines. By encoding video luma and chromaticity in two separate channels, it provides a better picture than composite video, which encodes all video data in one channel. It also removes various types of graphics, such as point inputs in composite videos. Although S-Video is an improvement over composite video, it has a lower color resolution than the video before us.
In late 1979, the Atari 800 was the first model to introduce separate color and brightness outputs. However, S-Video wasn't widely accepted until JVC introduced the S-VHS (Super VHS) format in 1987, so it can sometimes run into problems. It is not called "hyper video." Before the transition to digital video, the S-video format was widely used by consumers but was rarely used in offices, where YPbPr or products were often preferred.
Signal
S-video cables use two sync signals and a ground pair (called Y and C) to transmit video.
- Y is the brightness signal that sends the brightness (or black and white) of the image, including the synchronization pulse.
- C is the chromaticity signal that carries the chromaticity (or color) of the picture. These signals have two different colors.
The luma signal carries horizontal and vertical sync pulses in the same way as the composite signal.
In mixed video, the signals are combined at different frequencies. To achieve this, the signal brightness must be too low to be filtered, resulting in a dark image. Since S-Video stores the two signals as separate signals, there is no need for unwanted low-level luminance measurement, although the color signal still has a limited bandwidth compared to video film.
S-Video's color resolution is limited to 3.58 MHz (NTSC), or 4 compared to Component Video, which carries the same color signal but separates different color signals for Cb/Pb and Cr/Mr.
43MHz (PAL). This difference is of no value for home video, as Chroma is already limited to VHS and Betamax.
Carrying color information as a signal means that the color must be encoded in some way, usually NTSC, PAL, or SECAM, depending on the local standard.
Background of the S video
A standard analog TV signal goes through several processing steps during transmission, each of which skips information and distorts the final image. Images are initially captured in RGB and then processed in three formats called YPbPr. The first signal, called Y, is created from all three raw signals according to a pattern that creates the overall brightness of the image. The signal is similar to a black-and-white TV signal, and the Y/C encoding method is important to ensure a good relationship. When the Y signal is produced, it is subtracted from the blue signal to produce Pb and the red signal to produce Pr.
To restore the original RGB data to the screen, the signal is mixed with Y to produce blue and red, and then the numbers of the signal are mixed with Y to turn green.
A three-point signal is not much easier to broadcast than the original three RGB signals, so more needs to be done. The first step is to combine Pb and Pr to form a C signal used for chroma. The phase and amplitude of the signal represent two important signals. This signal is then bandwidth-limited to meet the requirements of the broadcast. The resulting Y and C signals are combined to create a composite video. To create a composite video, the Y and C signals must be separated; it is difficult to do this without adding artifacts.
Each of these steps leads to a serious or irreversible malfunction. As many encoding and decoding steps as possible should be removed to preserve this quality in the final image. S-Video is the solution to this problem. Later, it removes the final union and separation of C and Y.
Main Difference Between Composite and S-Video in Points
- Composite video was mostly in use during the 1980s in older forms of game consoles, television sets, and VCRs. The S-Video cable standard was used for the first time in JVC's S-VHS in 1987. It was during the late 1990s that larger television sets started combining S-Video, making it compatible with DVD players, satellite receivers, and video game consoles.
- Initially, composite video was used on larger televisions and earlier versions of VCRs. It has gradually been replaced by S-Video due to its better picture quality and is widely used as a replacement for TVs, high-end VCD players, video game consoles, and graphics cards. While the composite signal is good, S-video is more popular because of its better image quality.
- Composite video costs less to install than S-Video. The cables and adapters required to install the latter are more expensive. Today, the price difference is less significant as both have been replaced by HDMI.
- Both S-video and composite video are based on analog video signals. All work with PAL, NTSC, and SECAM encoding standards. However, their connectors are different from each other.
S-video signals generally use cables with 4-pin mini-DIN connectors, similar to mini-DIN cables. Yes, cables are easy to use, but they don't look good. The connectors are decent value, but the pins are not good and can bend after heavy use. Before these cables, simple plugs capable of carrying S-Video signals were used for the same purpose. On the other hand, composite video uses a yellow RCA connector or 1/8" jack plug, especially when a fixed device is used. There are devices that connect with four connectors when gaming devices use the same red light.
- S-video transfers a picture via two signals, named chroma (color) and luma (luminance). This video signal is of far better quality than what composite video has to offer. On the other hand, composite video is an analog signal that transfers a video or picture via a single signal that is of low quality. In the composite video, the luminance signal is low-pass filtered to avoid cross-talk between the color subcarrier and luminance data. This luminance data is multi-frequency in nature. However, S-video separates the two signals, so this low-pass filtering is not necessary. This automatically provides a wide brightness bandwidth and reduces the intensity of the color crosstalk problem. This will help provide a clearer image by keeping the original video's data in good condition.
Conclusion
Overall, S-video has a much better picture quality than composite signal, and it is a more updated version that is widely used as a replacement for high-end VCR players, video game consoles, television sets, etc. S-video carries a picture through two signals, namely chroma and luma, whereas composite video transfers a picture through only one signal. While composite signal cannot be considered unreliable or bad, and it has also been used in the early 80s and '90s, S-Video is just better than composite signal and has been used more and more from the late '90s until today. Over time, the demand for composite signals has greatly decreased, while that for S-Video has only recently grown. Today, S-Video is more in demand and used than composite signals.
References
- https://www.sony.com/electronics/support/articles/00032169#
- http://www.makify.com/composite-vs-s-video-vs-component/
- https://en.m.wikipedia.org/wiki/S-Video
- https://en.m.wikipedia.org/wiki/Composite_video#:~:text=A%20composite%20video%20signal%20combines,the%20chrominance%20or%20color%20information%20(
