Digital Video Interface (DVI) cables are self explanatory. It is an interface used for video display that connects a video source with any display device, for example, it connects the computer monitor with the processor.
What is a DVI?
Before the development of any technology there are certain factors and requirements that have to be fulfilled. When DVI was created, it was made as a standard that would transfer different digital film content to and from a display device. Uncompressed digital video is transmitted and is usually arranged to support several analog and digital modes.
Since the interface was compatible with analog connections and at times also with VGA interface, it became popular throughout the computer industry. Though it usually set up in computer equipments it is also available for HDTVs and DVD players.
Types of DVI Formats
There are three basic types of DVI cables that are available in the market: DVI-Analog, DVI-Digital and DVI-Integrated (a combination of analog and digital).
This type of cable is used when a DVI computer is connected to a VGA monitor. A VGA monitor can be a CRT monitor a budget LCD. The cable is used for VGA devices because it carries the same signals. Since the signals are converted from digital to analog and then back to digital, there some minor loss of quality. That is why it is advised that digital signal should be used when and where possible.
These cables provide direct digital connection between the LCD monitor and source device (it is usually a video card). As the signals are not converted to analog or any other format, the image quality is much higher and the signals travel much faster. The digital signal travels without and hindrance or conversion directly to the display device and the video is displayed.
These cables provide the best of both analog and digital worlds. The cables can easily transmit analog-to-analog signals and digital-to-digital signals. Because of this versatile feature the cable can be used for both analog and digital situations.
This does not mean that the analog and digital formats are interchangeable. In other words a digital DVI cable will not work on any analog structure and an analog DVI will not work on any digital system. A VGA to DVI-D converter would be needed to connect an analog source to a digital one. There are however, no converts currently available to connect digital output devices to analog monitors.
The video transmission of DVI cables is based on a serial format that uses TMDS, which stands for Transition Minimized Differential Signaling. For displays that use analog technology, it is important that all DVI devices support at least one low pixel format (640x480 at 60 Hz). Using multiple TMDS links the digitally programmed video pixel data is transferred from the output device to a display device. The TMDS links can be single links or dual links.
Single Link DVI
Four TMDS links are present in these DVI cables. Each link is responsible to transfer information from the source to the gadget over 1 pair of twisted wire. The clock frequency of 165 MHz is required for the transfer of pixels on a single link DVI cable.
Dual Link DVI
For display devices that require a high video bandwidth, a dual link DVI cable is used. Modes of display that need over 24 bits per pixel and have a clock frequency higher than 165 MHz, are mandated to use a dual link DVI cable. If a dual link is used for display modes with lower frequency and number of pixels, the data is striped across both links by the transmitter.
DVI Cable Length
The length of all DVI cables should be at least 16 feet or 5 meters in length according to the official DVI specifications documentation. Cables of varying lengths are available with lengths as small as 3 feet and as large as 75 feet. To have good signal quality that is available with every connection, you should use a powered DVI signal booster.
Unlike other video cables like component cables, DVI cables have to maintain a certain length. The video quality can be affected because of the length of the cable. When the cable has some fault in the wiring or is too long or it has just run its course, the screen will show you sparkling pixels or flicker and shake and it will eventually turn blank.
For DVI Integrated cables, the length is very crucial. Extensive lengths may cause the image to appear a bit blurred if it is run on digital signals. If the digital signal is very weak, the cable might automatically shift to an analog system as it can be easily transmitted over longer distances.
Which DVI Cable to Choose?
Since we have already discussed that there are three broad categories of DVI cables, it is important that you choose the right cable when making a purchase for the first time.
- If either one or both of the connecters have a DVI-D setup you need to buy a DVI-D cable.
- If either one or both connecters have DVI-A setup you need a DVI-A cable.
- If both connections are DV- integrated it is recommended that you use a DVI-integrated cable however any DVI cable can be used.
To understand which type of DVI cable to by, check the connectors. If the connector has a flat pin only that a DVI-D cable should be bought. If the connector has a flat pin that is surrounded by pins than either a DVI-A or a DVI-integrated cable needs to be bought.
For DVI-D cables it is important to follow the standards that are defined by the digital display working group (DDWG). This way the cable will deliver a high bandwidth interface that is required for all modern video displays along with high performance. At the same time, the cable leaves space for products that are to be developed in the future so that the cable can be easily modified according the standards.
More information about features and specs can be found on Wikipedia