According to abbreviationfinder, DVI is an acronym that comes from (” D igital V isual I nterface “), which when translated means digital visual interface. It is a semirectangular connector with 24 or 29 terminals, which is responsible for sending the signals referring to the graphics from the computer to a screen to be shown to the user. By allowing the sending of data between an external device (peripheral), with the computer, it is called a port.
This standard competes against VGA connectors, HDMI connectors, and S-video connectors.
DVI port characteristics
- It is a semi-rectangular connector, designed by the “Digital Display Working Group” (DDWG).
- It is designed to maximize the visual quality of flat screen video devices.
- It has ” Plug & Play ” possibilities, that is, when the device is connected to the computer, it automatically works without the need to install drivers (” drivers “).
- They use a “PanelLink” data format, called TMDS (“Transition Minimized Differential Signaling”) or signaling with minimized differential transition, which does not use any type of compression.
- The DVI port is responsible for sending the signals from the computer to the screen.
- It is commonly found in graphics accelerator cards and video capture cards.
DVI Port / Pinout DVI Electrical Terminals
Pinout means output tip, there are 2 DVI versions: the most used has 24 terminals and another with 29 terminals, the following figure shows the electrical lines and their basic description only of the first one.
- TMDS 2-
- TMDS 2+
- TMDS Data 2/4 Shield
- TMDS Data 4-
- TMDS Data 4+
- DDC Clock
- DDC Data
- Analogic Vert Sync
- TMDS Data 1-
- TMDS Data 1+
- TMDS Data 1/3 Shield
- TMDS Data 3-
- TMDS Data 3+
- +5 Volts Power
- Hot Plug Detect
- TMDS Data 0-
- TMDS 0+
- TMDS Data 0/5 Shield
- TMDS Data 5-
- TMDS Data 5-
- TMDS Clock Shield
- TMDS Clock +
- TMDS Clock –
DVI port lines for video.
The DVI data format is based on the PanelLink serial format, developed by semiconductor manufacturer Silicon Image Inc. It uses TMDS(“Transition Minimized Differential Signaling”).
A DVI link consists of a cable of four twisted pairs: one for each primary color (red, green, and blue) and one for the “clock” (which synchronizes the transmission). The timing of the signal is almost the same as that of an analog video signal.
The image is transmitted line by line with erasure intervals between each line and between each frame. No compression or packet transmission is used, and it does not allow for only shifted areas of the image to be transmitted. This means that the entire screen is constantly streamed.
With a single DVI link (or Single Link), the highest possible resolution at 60 Hz is 2.6 megapixels. For this reason, the DVI connector supports a second link (Dual Link), with another set of twisted pairs for red, green and blue. When more bandwidth is required than a single link allows, the second is activated, and the two can output alternating pixels.
The DVI standard specifies a maximum limit of 165 MHz for single links, so that display modes that require a lower frequency should use the single link mode, and those that require more should set the dual link mode. When both links are used, each can exceed 165 MHz. The second link can also be used when more than 24 bits per pixel are needed, in which case it transmits the least significant bits.
A the same as the VGA analog connectors modern, the DVI connector has pins for the data channel screen version 2 (DDC 2) that allows the graphics adapter to read data Extended Display Identification (EDID, “Extended Display Identification Data”).
Older standards, such as VGA, are analog and designed for CRT (cathode ray tube or cathode tube) devices. The source varies its output voltage with each line it emits to represent the desired brightness.
On a CRT screen, this is used to assign the beam to the proper intensity as it scrolls across the screen. This ray is not present on digital screens; instead there is an array of pixels, and a brightness value must be assigned to each of them. The decoder does this task by sampling the input voltage at regular intervals.
When the source is also digital (such as a computer), this can cause distortion if the samples are not taken in the center of each pixel, and, in general, the degree of noise between adjacent pixels is high.
DVI takes a different approach. The brightness of the pixels is transmitted in the form of a list of binary numbers. When the screen is set to its native resolution, you just have to read each number and apply that brightness to the appropriate pixel.
In this way, each pixel in the source’s output buffer corresponds directly to a pixel on the screen, while with an analog signal the appearance of each pixel can be affected by its adjacent pixels, as well as electrical noise and others. forms of analog distortion.
Important DVI monitors
- The IBM T221 monitor debuted in early 2003, and features four single-link DVI connectors and a resolution of 3820 × 2400, or nearly 9.2 million pixels. Connected to a single link graphics card, its refresh rate is only 13 Hz. It can reach 41 Hz by connecting all four connectors to graphics cards.
There are later models that can be connected to a DVI dual-link graphics card, thus obtaining a frequency of 24 Hz, although this is achieved by using an external splitter box that converts the dual-link signal into two single-link signals for the monitor.
- Screen Cinema HD Display 30 – inch Apple Computer debuted in mid-2004 and was one of the first screens of the market to use a dual – link DVI connection. Its native resolution is 2560 × 1600, about 4.1 million pixels.
- Minimum clock frequency: 21 Hz Maximum clock frequency for single link: 165 MHz
- Dual Link Maximum Clock Rate – Limited by Cable Only
- Pixels per clock cycle: (single link) or 2 (double link)
- Bits per pixel: 24
- Display modes (single link):
- HDTV (1920 × 1080) at 60 Hz with 5% LCD blanking (131 MHz)
- 1920 x 1200 @ 60 Hz (154 Mhz)
- UXGA (1600×1200) @ 60Hz with GTF blanking (161MHz)
- SXGA (1280 × 1024) at 85 Hz with GTF blanking (159 MHz)
- Display modes (dual link):
- QXGA (2048 × 1536) at 75 Hz with GTF blanking (2 × 170 MHz)
- HDTV (1920 × 1080) at 85 Hz with GTF blanking (2 × 126 MHz)
- 2560 × 1600 (on 30-inch LCD screens)
GTF (“Generalized Timing Formula”) is a VESA standard.
- RGB bandwidth: 400 MHz at –3 dB.
Advantages of the DVI connection over the VGA connection.
Graphics card with VGA & DVI monitor outputs and S-Video TV output.
Not long ago the DVI port began to be used for graphic card connections and it has quickly become established, to the point where not only the vast majority of graphic cards have this type of connection together with the VGA connection usual until now, but more and more high-end graphics cards, and even mid-range, that only have DVI ports.
Given this, it is logical to ask what are the differences between these two types of ports, as well as which of them is better.
To do this, you will see what type of ports you are talking about and how they work, as well as what type of screens (monitors) they are used on.
The VGA connector is the one normally used to connect the output of our graphics card to the monitor.
Although they are known as VGA (V ideo G raphics A RRay), really existing connectors do not work under the VGA standard, which lets you display up to 256 colors from a palette of 262,144 colors with a maximum resolution of 720×480 and a soda maximum 70Hz but SVGA (S uper Video G raphics A rray), which allows a resolutions and color palettes far greater, as are used.
These two systems use the same type of connector, called VGA D-sub 15-pin.
But this type of connector, which works quite well for CRT type monitors, is not capable of providing sufficient image quality when it comes to TFT monitors or other similar types. This is because, whatever the type of graphics card it is, the connection with the monitor is made in an analog way. The color depth is defined by simple voltage, so in theory an SVGA or VGA monitor (of the CRT or Cathode Ray Tube type) has practically no limit in terms of the number of colors it is capable of displaying.
The brightness of each color is determined by a variation in the intensity of the beam as it travels along the corresponding line.
But this does not happen in the same way when it comes to a TFT monitor, which as we know are the ones that are mostly used today. And this is so because this type of screen does not use this cathode ray system, but rather works with a matrix of pixels, and a brightness value must be assigned to each of them.
This is done by the decoder, which samples input voltages at regular intervals. This system poses a problem when both the emitting source (in this case the card) and the receiving source (in this case the TFT monitor) are digital, since it forces to take this sample from the very center of the pixel, to avoid noise. and color distortions. This causes, among other things, that both the tone and the brightness of a pixel can be affected by those of the pixels around it.
In the DVI format this is done differently, since it is a digital format, so the brightness of each pixel is transmitted by binary code. This means that when a TFT screen works with a DVI connection and in its native resolution (we must remember that TFT screens have a native resolution, which is where they give their highest quality) each output pixel corresponds to a pixel on the screen., which makes the pixels have all their color, quality and brightness. Obviously, for this to happen, both elements (graphics card and monitor) must have digital connections (DVI or HDMI).
But not all monitors have this type of connection, which is why there are DVI-VGA adapters on the market, since as we have said, most graphics cards are adopting this type of connection, even eliminating VGA connections in many cases.
This is so because DVI connectors are capable of transmitting both analog and digital signals in one of their models (DVI-I), which is the one used by graphics cards.
Types of DVI connectors
There are several types of connectors, depending on the types of signal they are capable of transmitting:
Three of them are shown in the image above.
DVI-D transmits digital only. DVI-A transmits only analog. DVI-I transmits both digital and analog signals.
In turn, DVI-D and DVI-I types can be dual (DL or Dual Link), that is, they can support two links.
Battle between DVI and HDMI
If the battle between HD-DVD and Blue-ray has been tough, although it seems to lean towards the latter technology, the one between DVI and HDMI has been quieter, but it seems that it also has a clear winner, HDMI.
According to a report by In-Stat, the decrease in the number of devices that incorporate DVI will be very marked from 2008 to 2011, going from 112 million to only 3 in these years. On the other hand, HDMI grows more and more, and this year 143 million devices with support for it are expected to be distributed.
HDMI has passed its hand in the face of DVI, especially in the field of mass consumption devices such as televisions, consoles, cameras, both video and photos,… The fact that it incorporates sound in the same cable is one of the factors that facilitate their implementation, as well as the fact that the connectors are smaller and more manageable, similar to the USB but smaller, unlike the DVI, whose connectors are the same style as the VGA ones that they have tried to replace.
In computers, where DVI has been widely implemented for connection to monitors, it is likely to be quickly replaced by DisplayPort, which incorporates some of the innovations that HDMI already has.