Video Connections
There are numerous ways to connect a video source such as a DVD player to a television or other home cinema components. This page explains the different types of video connection available and how they work.
VIDEO CONNECTIONS

INTRODUCTION

Lets begin with the television. Traditionally, televisions have only needed one type of input to accept the single coaxial antenna socket. The signal from the roof mounted antenna was connected directly to the television. When video recorders became available, they simply fitted into the system using an extra length of coaxial cable. The antenna signal was fed into the VCR and out to the television allowing the TV to display pictures from television transmissions and from video tapes. With the further development of the technology behind televisions, video recorders and the fairly recent addition of more complex video sources, the coaxial cable has been joined by a number of high quality video connections in order to maximise the final picture quality.

 
   
 

SCART Cables

The next step forward from coaxial cable was the introduction of the Euroconnector, more commonly referred to as SCART. It uses sockets to both the TV and the VCR, plus is the prime video connection used on satellite receivers, laserdisc players and DVD-Video. The SCART cable has up to 21 separate cables within the main cable and allows picture components and audio channels to be separated during transfer between the components. SCART cables are also bi-directional, allowing information to pass back from the TV to the VCR. Today, SCART connections are the most commonly used type of link between video recorders, video sources and televisions. In its basic form, a SCART cable carries one or two audio channels in each direction, plus a combined video signal (see Composite Video below), and most of the 21 cables are unused. For higher quality pictures, the video signal can be split into its component parts before being sent through the SCART cable. Further down this page you will find information about S-Video, RGB Video and Component Video connections. A SCART cable with all 21 wires fully connected can be utilised to carry each one of these superior types of transfer. This is done by allocating an individual wire within the SCART cable to a single component of the picture signal rather than combining them into a Composite signal. Because it is not necessary to combine the components from the source and separate them again at the television, the signal can be transferred with less information being lost.

   
 

Composite Phono Video

Composite video is a single phono cable connection that carries picture information only from the source to the TV. They are usually found together with a pair of standard audio phono sockets, one for left stereo and one for right stereo. These three phono sockets offer high quality audio and reasonable quality video connections between components with suitable inputs and outputs. Composite video inputs are found on the front panel of many video recorders and televisions to allow connection of a camcorder. As more Home Cinema sources gained a composite video output, these sockets have been used to connect these sources. As the name suggests, this type of connection is used to send a composite signal made up of all the different elements of the picture signal, such as colour, luminance, etc. The source video signal must be combined before it is sent through the cable, and it must be separated by the television at the other end to build a picture that can be seen. The downside of this process is that a small amount of picture information is lost during transfer. For this reason, other types of video connections have found their way into home cinema to maintain the highest possible signal quality. These are described below.

   
 

S-Video

S-Video is a video only cable (with no audio information) and is probably the best type of connection for transferring picture information from a source to a television within most Home Cinema systems. Nearly all DVD players have an S-Video output, and an ever-increasing number of televisions are being equipped with S-Video inputs. The single-cable plugs are split into four separate pins that each carry different parts of the picture signal, thus reducing internal signal interference and reducing quality-loss as a result of combining a Composite video signal. Two of the pins carry Brightness information, known as luminance (Y) while the other two carry Colour information known as chrominance (C). This is why sometimes S-Video is called a Y/C connection. The S-Video standard was originally developed in the late 1980's to transfer high resolution pictures from the new S-VHS video recorders. Although S-VHS may not have caught on as much as was hoped, the S-Video connections have been widely adopted for Home Cinema and can now be found on DVD players, video recorders and surround sound amplifiers (see "Video Switching" below). SCART cables are capable of carrying an S-Video signal by allocation separate wires to carry the information normally found in the S-Video cable. To use SCART, the hardware at each end of the cable must be able to handle an S-Video SCART - not many do, however.

   
 

Red/Green/Blue (RGB)

The next best type of video connection is called RGB and consists of three outputs on the back of an RGB equipped video source. Some components, such as televisions and DVD players, can also use RGB signals through a fully-wired 21-pin SCART cable, where three separate wires within the SCART are used for the three components. Because each colour has its own cable, the amount of signal loss it reduced, allowing the signal to arrive at the monitor in a higher-quality form. RGB can commonly be found as an input on the back of projector units, as television and video SCART connections, and on DVD players as either SCART outputs or as three individual outputs, one for each colour. A picture signal using RGB is sent as the three primary colours, Red, Green and Blue, from which all the other colours that make up a picture are created. A further signal containing luminance (Y) information is carried 'piggy-back' with the Green and Blue signals.

   
 

Component Video

Component Video signals are generally used on front-projection systems and computer systems and produces the very best results. Taking the form if a 5-pin DIN plug at each end of a single cable, the picture signal is transferred as Red, Green, Blue, Horizontal Timing and Vertical Timing. This is picture information in its purest form.

   
   

CONNECTING VCR TO A TELEVISION

This is the easy bit and most people will have this setup in their homes already. The roof antenna is connected to the VCR and the VCR to the TV using coaxial antenna cable. The VCR is also usually connected to the TV using a SCART cable for better sound and picture performance when watching television transmissions or video tapes. Practically all video recorders and televisions now come with a SCART sockets.

 
Video To TV
 
   

ADDING A SATELLITE RECEIVER

The satellite receiver fits into the TV/VCR system at the top of the chain, before the VCR. Both the roof antenna and the satellite dish are connected to the receiver using coaxial cable. A single coaxial cable links the satellite receiver to the video recorder. SCART cables can be added to connect the receiver to the video recorder and then to the television (SCART 1). If a second SCART socket is provided on both the television and the receiver, a SCART cable can be used to connect the two, therefore bypassing the video recorder when it is not in use (SCART 2).

 
Video and Satellite to TV
 
   

ADDING MORE VIDEO SOURCES

This is the point an which some people encounter problems due to a shortage of SCART sockets. There is no problem if your television has two or three SCART inputs - you simply connect the new source directly to the television. The only disadvantage of this is that you can't record the output from the new source onto tape using the video recorder, as the signal passes to the TV rather than through the VCR like the satellite receiver does. It may also be possible to connect the new source to the VCR in place of the satellite receiver, in systems that don't use satellite television.

 
Adding a DVD player
 
The system shown above is great if you have all the necessary SCART sockets and if you intend to use the components as shown. The problem arises when you want to add more video sources and have no more inputs to use. There are two ways that additional components can be added to the system shown above, or even in the systems shown towards the top of the page. The first option is to add a SCART Switchbox, and the second is to use "video switching" features found on most A/V amplifiers.  
   

SCART Switchbox

When I first ran out of SCART sockets, I used a SCART switchbox to combine multiple inputs into a single SCART connection. All the additional SCART cables are connected to the switchbox, and a single SCART lead sends the signal from the selected source to either the video recorder or the television, as shown in the diagram below:

 
SCART Switchbox
 

The audio information is also passed along the SCART cables beside the picture. Audio information could be sent to a suitable amplifier directly from the source using separate phono interconnects, if the amp has enough phono inputs. The switchbox shown above can also help if the amplifier has too few audio inputs. Using the switchbox, all the audio is sent to the VCR or TV. The sound information can then be sent from the VCR or TV to an amplifier using a single phono interconnect, rather than a separate interconnect from each component.

 
   

VIDEO SWITCHING

You may have seen reviews of A/V amplifiers or receivers that have a number of inputs with "video switching". This is a useful way to connect a number of video source components to a home cinema system. A normal amplifier has several audio inputs for connecting various sources. When the input selector on the amplifier is adjusted, the sound is heard from the selected component. Video switching works in the same way. Next to the audio inputs for each component, a video input has been added, either a composite phono type or S-Video. Each of the video source components can be connected to the A/V amplifier, provided they have the necessary type of output. A single video output will be included on the A/V amp that is used to send the received video signal from the source to a television. When the input selector is adjusted on the A/V amplifier, both the audio and the video signals pass through the unit - the audio going to the speakers and the video going to the television via the video output. In effect, multiple sources can be connected to a television using a single video input.

SCART sockets are not used on components with video switching, due to the lack of space on the back of the unit, but mainly due to the higher quality of S-Video connections.

 
Video Switching