Introduction
The letters DVI stand for Digital Video Interface, sometimes referred to as a digital video connector. It is a standard developed to transmit digital video content to display devices. DVI appears on many older computers and is commonly found on computer monitors, projectors, and some televisions and other displays.
Although the standard is now relatively old, it can handle resolutions up to 2560 × 1600 at 60 Hz, while 1920 × 1080 remains the most widely used high-definition format.
Despite its name, DVI is the only widely used video interface that accommodates both analog and digital signals. Some cables and connectors carry both formats to maintain compatibility with legacy equipment.
Overview
The DVI standard was developed by the Digital Display Working Group and introduced in April 1999. It replaced the VGA standard and related connectors and provided a useful transition as the industry moved from analog to digital displays.
DVI versions can carry both digital and analog signals when both ends of the link support them, making it an ideal transitional interface between the two technologies.
Basics
DVI's primary role is to provide a digital video interface, while analog support was included to preserve compatibility with older analog devices that were still widely used when the standard was introduced.
There are three main DVI variants:
- DVI-A: The analog-only form of DVI. It supports only analog signals and the connector is populated accordingly.
- DVI-D: The digital-only form of DVI. It supports only digital signals and its connector omits the analog pins.
- DVI-I: The integrated form that supports both analog and digital signal formats.
The DVI digital video interface uses the panelLink serial data format originally developed by Silicon Image. Digital video is transmitted using transition-minimized differential signaling.
This is based on a high-speed serial link format called Transition Minimized Differential Signaling (TMDS). Data is transmitted over multiple twisted-pair conductors; using twisted pairs provides good immunity to radiation and stray pickup, improving link robustness.
Data is formatted using 8b/10b encoding. Video is sent as rasterized data, effectively representing a digitized form of the analog scanning process: the analog beam scanned each line and then returned to the start of the next line, so DVI carries data in a similar per-line raster format.
When a source and a receiver connect, the source queries the display to discover its capabilities. The display shares Extended Display Identification Data (EDID) containing parameters such as gamma, color characteristics, supported video mode list, native resolution, and preferred timing.
Each mode defines a set of CRT-compatible timing values for horizontal and vertical sync and parameters such as vertical and horizontal resolution, active display area, and refresh rate. As a result, a full frame is carried during each vertical refresh, and the active area of each frame is not compressed.
Because of CRT compatibility requirements, video modes typically use horizontal and vertical timing compatible with CRT operation, and the DVI data format accommodates these needs.
Single-link and Dual-link
DVI supports two digital interface bandwidth levels: single-link and dual-link.
Single-link
Single-link is the basic DVI-D link level. It provides four TMDS pairs for data transmission. Three data pairs carry 8-bit RGB color components for red, green, and blue. The fourth pair mainly carries the pixel clock data.
The maximum clock frequency is 165 MHz, which corresponds to a maximum of approximately 2.75 million pixels including blanking intervals at a 60 Hz refresh rate.
Dual-link
Dual-link is used to support higher-resolution displays. Dual-link DVI doubles the number of data pairs, providing increased bandwidth. Dual-link DVI-D raises the maximum achievable resolution to 2560 × 1600 at 60 Hz for supported displays.
Cable Length
The DVI standard does not define a maximum cable length, but practical limits depend on the TMDS clock frequency. For 1920 × 1080 HD signals, a maximum reliable length is typically around 4.5 meters. Lower resolutions can use longer cables; for example, 1280 × 1024 may reach up to about 15 meters.
If longer distances are required, DVI signal boosters or repeaters should be used to restore the signal and provide the necessary extension. Without signal conditioning, display resolution may drop or data errors may occur. Choosing a high-quality cable of appropriate length helps ensure optimal performance.
Connectors and Pinouts
DVI connectors are a distinctive low-force helix-type connector. A full DVI connector can present up to 24 pins arranged in a three-row matrix, forming the main digital region of the connector. In addition, analog-capable connectors include four extra pins for analog signals. Besides the standard full-size connector, mini and micro versions exist but are rare.
Although the physical shape is similar across variants, different connector versions populate different pin sets depending on the supported signals and functions.
Legacy Status
DVI is now an outdated standard and is not typically included on new electronic and computer devices. However, it remains present on many older monitors, screens, and projectors. DVI served well during the transition from CRT-based analog displays to digital displays because its rasterized data format matched the line-by-line scanning behavior of CRTs.
While some displays and projectors still use DVI, it has become less common as newer digital interfaces have been adopted.
