What are the types of DVI interfaces?

The DVI interface is a technology for high-speed transmission of digital signals invented by the Digital Display Working Group (DDWG) established at the Intel Developer Forum in September 1998. There are three different types of interfaces: DVI-A, DVI-D, and DVI-I. DVI-D has only a digital interface, while DVI-I has both digital and analog interfaces. Currently, DVI-D (24+1) is the main application.

DVI (Digital Visual Interface) is a digital video interface. It was established in September 1998 at the Intel Developer Forum and was launched by the DDWG (Digital Display Working Group) composed of Silicon Image, Intel, Compaq, IBM, HP, NEC, Fujitsu and other companies. DVI is based on TMDS (Transition Minimized Differential Signaling) technology to transmit digital signals. TMDS uses advanced coding algorithms to convert 8-bit data (each primary color signal in R, G, B) into 10-bit data (including line field synchronization information, clock information, data DE, error correction, etc.) through minimum conversion. After DC balancing, it uses differential signals to transmit data. Compared with LVDS and TTL, it has better electromagnetic compatibility performance and can use low-cost dedicated cables to achieve long-distance, high-quality digital signal transmission. Digital Video Interface (DVI) is an international open interface standard that is widely used in PCs, DVDs, high-definition televisions (HDTVs), high-definition projectors and other devices.

The full English name of DVI is Digital Visual Interface. It is a video interface standard designed to enhance the image quality of personal computer monitors through digital transmission. It is currently widely used in display devices such as LCDs and digital projectors. In addition to the digital signal pins specified by the DVI standard, the DVI connector can also include pins for traditional analog signals (VGA). This design is to maintain the versatility of DVI so that different types of screens can share the same connection cable. According to their implementation functions, DVI connectors can be divided into three types:

DVI-D (D = digital, only transmits digital signals): digital signal interface, can only receive signals from the DVI-D interface. There are only 24 pins in 3 rows and 8 columns on the interface, one of which is empty in the upper right corner and is not compatible with analog signals.

DVI-A (A=analog, only transmits analog signals): Analog signal interface, can only connect signals from DVI-A or VGA interfaces.

DVI-I (I=AD=integrated, can transmit digital and analog signals): includes two interfaces, DVI-A and DVI-D, which are compatible with both analog and digital signals. Compatible with analog signals does not mean that the interface of analog signals D-Sub interface can be connected to DVI-I interface, which can only be used through an adapter. Generally, graphics cards with this interface will come with corresponding adapters.

Nowadays, when people buy LCD monitors, they generally know in advance that it is best to buy models with DVI interfaces. However, although they are all called DVI, they are actually divided into three types; and different types of DVI have very different functions.

DVI includes three versions: DVI-A, DVI-D and DVI-I.

Analog, DVI-Digital and DVI-Integrated, while DVI-A is just a DVI that is used to fill in the gaps. In fact, the so-called DVI-A is just the DVI representation of VGA, so DVI-A is actually an analog interface. However, DVI-A has been basically eliminated, and the DVI used by mainstream LCDs is generally not DVI-A.

The difference between DVI-D and DVI-I is that DVI-D can only transmit digital signals, while the complete DVI-I is compatible with both digital and analog signals. In fact, DVI-I is a combination of DVI-A and DVI-D. In terms of form, the DVI-D interface has 3 rows and 3 columns with a total of 24 pins, of which a pin in the upper right corner is empty. This "missing" empty pin corresponds to the analog I/O. DVI-D/I is divided into two types, namely single-channel and dual-channel versions. DVI-I also has 3 rows and 3 columns with 24 pins, but there are 5 more pins on the right to support analog I/O. As for the difference between single-channel and dual-channel DVI-D/I, the single-channel DVI-D/I actually only has 18 defined pins, so its transmission rate and refresh capacity are only half of that of the dual-channel DVI-D/I.

In terms of specific performance, dual-channel DVI-I is the most powerful, but the cost is higher, while ordinary LCDs mostly use DVI-D and single-channel DVI-I. Generally, dual-port LCDs that retain the VGA interface are configured with DVI-D, while some single-port DVI LCDs use the DVI-I interface.

In terms of compatibility, DVI-A and DVI-D are incompatible with each other, while DVI-I is compatible with DVI-D (including the connecting cable), but DVI-D is not compatible with the DVI-I connecting cable. In addition, the maximum refresh rate of the single-channel DVI-I interface can only support 1920*1080@60Hz or 1600*1200@60Hz, so it is more difficult to cope with LCDs above 22 inches, and the display quality may decline. When purchasing a large-screen LCD, this detail must be carefully examined. At present, the DVI configured in most graphics cards on the market is still a single-channel version of DVI-D or DVI-I.