What is DVI (Digital Visual Interface)?

DVI (Digital Visual Interface) is a 24 or 29 terminal semi-rectangular connector that is responsible for transmitting graphic signals from a computer to a screen and displaying it to the user.

What is DVI (Digital Visual Interface)?

What is DVI Port?

Allows data to be sent between the computer and an external device (peripheral). These standard VGA connectors compete with HDMI connectors and S-video connectors.

Specifications

It is a semi-rectangular connector designed by DDWG (Digital Display Working Group). It is designed to maximize the visual quality of flat-screen video devices. It has Plug and Play features, so when you connect the device to the computer, it automatically runs without installing the drivers.

They use the PanelLink data format called TMDS (Transition Minimized Differential Signaling) or minimized differential transition that does not use any compression type.

The port is responsible for sending signals from the computer to the screen. It is often found in graphics accelerator cards and video capture cards.

Technical Specifications

Data format, semiconductor manufacturer Silicon Image Inc. It is based on the PanelLink serial format developed by.

A DVI connection consists of four twisted-pair cables, one for each primary color (red, green and blue) and one for the watch. The signal timing is almost the same as that of an analog video signal.

The image is transmitted line by line, with spacing between each line and between each frame. Compression or packet forwarding are not used and do not support the transmission of only varying areas of the image. This means that the entire screen broadcasts continuously.

The maximum possible resolution at 60 Hz with a single DVI connection (or Single Link) is 2.6 megapixels. Therefore, the connector supports a second link (Dual-Link) with another twisted pair set for red, green and blue. When more bandwidth is required than a single connection allows, the second link becomes active and both can emit alternative pixels.

The DVI standard sets a maximum limit of 165 MHz for single connections, so the display modes that require lower frequency should use the single connection mode and the modes that require more should set the dual connection mode.

When two connections are used, each can exceed 165 MHz. The second link can also be used when more than 24 bits per pixel are required, in this case, it transmits the least important bits.

Like modern analog VGA connectors, the DVI connector also has pins for the display data channel, version 2 (DDC 2), which allows the graphics adapter to read EDID (Extended Display Identification Data).

Overview

The above standards, like VGA, are analog and are designed for CRT (cathode ray tube or cathode tube) devices. The source replaces the output brightness with each line it emits to represent the desired brightness.

On a CRT screen, this is used to assign the appropriate intensity to the beam as it moves across the screen. This beam is not available on digital screens; it is a sequence of pixels instead, and a brightness value must be assigned to each. The decoder does this by taking input voltage samples at regular intervals.

When the source is also digital (like a computer), if samples are not centered on each pixel, this may cause distortion and generally, the degree of noise between adjacent pixels is high.

DVI takes a different approach. The brightness of the pixels is transmitted as a binary list. When the screen is set to its native resolution, it reads every number and applies this 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 the appearance of each pixel with an analog signal can be affected by adjacent pixels as well as electrical noise and other analog distortion patterns.

Monitors

The IBM T221 monitor was released in early 2003 and offers four single-link DVI connectors and a resolution of 3820×2400 or approximately 9.2 million pixels. The refresh rate, which is connected to the single link graphics card, is only 13Hz. By connecting all four connectors to graphics cards, you can reach 41Hz.

There are models that can be connected to a dual-link graphics card, so a frequency of 24 Hz is achieved, but this is accomplished by using an external splitter box that converts the dual-link signal into two single-link signals for the monitor.

The Apple Computer 30-inch Cinema HD Screen was released in mid-2004 and was one of the first screens on the market to use a dual-link connection. Its native resolution is 2560×1600, about 4.1 million pixels.

Digital Features

  • Minimum clock frequency: 21 Hz Maximum clock frequency for a single connection: 165 MHz
  • Maximum Clock Speed ​​for Dual Connection – Cable Only Limited
  • Pixel per clock cycle: (single link) or 2 (double link)
  • Number of bits per pixel: 24
  • Display modes (single connection):
    • HDTV (1920×1080) at 60 Hz with 5% LCD erase (131 MHz)
    • 1920×1200 at 60 Hz (154 Mhz)
    • UXGA (1600×1200) at 60 Hz with GTF erase (161 MHz)
    • SXGA (1280×1024) at 85 Hz with GTF erase (159 MHz)
  • Display modes (dual connection):
    • QXGA (2048×1536) at 75 Hz with GTF erase (2×170 MHz)
    • HDTV (1920×1080) at 85 Hz with GTF erase (2×126 MHz)
    • 2560×1600 (on 30-inch LCD screens)

GTF (Generalized Timing Formula) is a VESA standard.

Advantages

Not so long ago, the DVI port began to be used for graphics card connections and was quickly set up to the point where only the vast majority of graphics cards did not have this type of connection along with the VGA connection. But now there are more high-end graphics cards.

Given this, it makes sense to ask what are the differences between these two ports and which ones are better.

For this, you will see what kinds of ports are spoken and how they work and what kind of displays (monitors) are used.

   VGA Connector

The VGA connector is the connector normally used to connect the output of our graphics card to the monitor.

Although they are known as VGA, current connectors do not really work under the VGA standard, which allows a maximum of 720×480 to be displayed from the 262,144 color palette and a maximum of 256 colors with a resolution, the maximum refresh rate is 70Hz, but SVGA allows much higher resolutions and color palettes as we are accustomed to.

These two systems use the same type of connector called 15-pin D-sub VGA.

However, this type of connector, which works well for CRT monitors, cannot provide sufficient image quality when it comes to TFT monitors or other similar types. This is because it does an analog connection to the monitor, regardless of the type of graphics card. The color depth is defined by simple voltage, so there is virtually no limit to the number of colors an SVGA or VGA monitor (CRT or Cathode Ray Tube type) can display.

The brightness of each color is determined by a change in the intensity of the beam as it moves along the corresponding line.

However, as we know, this is not the case when it comes to a TFT monitor that is the most used today. And this is so because such a display does not use this cathode-ray system, instead it works with a pixel matrix and it is necessary to assign a brightness value to each.

This is done at regular intervals using a decoder that takes voltage input inputs. To avoid noise and discoloration, this system creates a problem when both the emitter source and the receiver source are digital because it requires taking the sample from the middle of the pixel. This, among other things, causes the tone and brightness of a pixel to be affected by that of the surrounding pixels.

   DVI Connector

In DVI format, this is done in a different way as it is a digital format so that the brightness of each pixel is transmitted using binary code.

This means that when a TFT screen works with a DVI connection and in its native resolution, each output pixel corresponds to the on-screen pixel and the pixels have full color, quality, and brightness. For this to happen, both items must have digital connections.

But not all monitors have this type of connection, so there are DVI-VGA adapters on the market because, as we said, most graphics cards adopt this type of connection and in many cases even eliminate VGA connections.

This is because this connector can transmit both analog and digital signals on one of the models (DVI-I) used by graphics cards.

Connector Types

There are several types of connectors, depending on the types of signals they can transmit:

  1. DVI-D broadcasts only digitally.
  2. DVI-A transmits a single analog.
  3. DVI-I transmits both digital and analog signals.

In contrast, DVI-D and DVI-I types can be dual (DL or Dual-Link), that is, it can support two links.

The Battle Between DVI and HDMI

If the battle between HD-DVD and Blue-ray seems to be leaning on second technology, the battle between DVI and HDMI was quieter, but it also seems to have a clear winner; HDMI.

HDMI has surpassed DVI especially in the field of consumer devices such as televisions, consoles, cameras, video, and photos. Including audio in the same cable, its connectors are the same style, similar to USB, smaller and more manageable.

On computers where DVI is most commonly applied for connection with monitors, it is likely to replace DisplayPort, which includes some innovations that HDMI already has.

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