DVI Connector: Types, Advantages, Distiguishment And Development

Catalog

A DVI connector is based on TMDS, which converts the smallest differential signal technology to transmit digital signals. TMDS uses advanced coding algorithms to encode 8bit data (each of the primary color signals in R, G, B) into 10bit data (including horizontal and vertical synchronization information) through minimum conversion, Clock information, data DE, error correction, etc.). After DC balance, it adopts a differential signal to transmit data. Compared with LVDS and TTL, it has better electromagnetic compatibility performance. It can use low-cost dedicated cables to achieve long-distance and high-Quality digital signal transmission.

I. Types

DVI connectors include DVI-A (DVI-Analog), DVI-D (DVI-Digital), and DVI-I (DVI-Integrated).

DVI-A is an analog signal connector, which can only transmit analog signals. Its essence is the VGA analog transmission interface specification, which is barely put into use now.

DVI-A

The DVI-D connector is a pure digital connector, which can only transmit digital signals and is not compatible with analog signals.

DVI-D

The DVI-I connector is compatible with digital and analog connectors. In order to be compatible with VGA analog signals, it has 4 more signal pins than DVI-D to transmit analog signals.

DVI-I

The difference between DVI-D and DVI-I

DVI-D can only transmit digital signals, and a 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 manifestation, the DVI-D connector has 24 pins in 3 rows and 3 columns, one of the pins in the upper right corner is empty, and this "missing" empty pin corresponds to analog I/O. The DVI-D/I is divided into two types, namely single-link and dual-link versions. Among them, the form of DVI-I is also 3 rows, 3 columns, and 24 pins, but there are 5 more on the right to support analog I/ O pin. As for the difference between single and dual-link DVI-D/I, single-link DVI-D/I actually has only 18 pins defined, so its transmission rate and refresh capability are only half of dual-link DVI-D/I.

In terms of actual performance, dual-link DVI-I is the most powerful, but the cost is higher, while ordinary LCDs mostly use DVI-D and single-link DVI-I. Generally, the dual-link LCD configuration that retains the VGA connector is DVI-D, and some single-link DVI LCDs use the DVI-I connector.

In terms of compatibility, DVI-A and DVI-D are not compatible with each other, and DVI-I can be compatible with DVI-D (including cable), but DVI-D is not compatible with DVI-I cable. In addition, the maximum refresh rate of a single-link DVI-I connector can only support 1920*1080@60Hz or 1600*1200@60Hz, so it is more difficult to deal with LCDs over 22 inches, and the display quality may decrease. When purchasing large-screen LCDs, this detail must be examined clearly. Currently, on the market, the DVI for most graphics cards is still a single-link DVI-D or DVI-I.

II. Advantages

1. Fast speed

DVI transmits digital signals, and digital image information will be directly transmitted to the display device without any conversion. Therefore, the cumbersome conversion process of digital → analog → digital is reduced, which greatly saves time. Therefore, It is faster, effectively eliminates the smear phenomenon. The signal is not attenuated by using DVI for data transmission, and the color is purer and more realistic.

2. Clear picture

the computer transmits a binary digital signal. If you use the VGA connector to connect to the LCD display, you need to first convert the signal to the R, G, and B three primary color signals through the D/A (digital/analog) converter in the graphics card And line and field synchronization signals, these signals are transmitted to the inside of the liquid crystal through the analog signal line, and the corresponding A/D (analog/digital) converter is needed to convert the analog signal into a digital signal again to display an image on the liquid crystal. In the above-mentioned D/A, A/D conversion, and signal transmission process, signal loss and interference will inevitably occur, resulting in image distortion and even display errors. The DVI connector does not need to perform these conversions, avoiding signal loss and making The image clarity and detail expression have been greatly improved.

3. Supporting HDCP protocol

The DVI connector supports the HDCP protocol, laying the foundation for watching copyrighted HD videos. However, if you want the graphics card to support HDCP, the DVI connector alone is not enough. You need to install a dedicated chip and pay a high HDCP certification fee. Therefore, there are not many graphics cards that really support the HDCP protocol.

Compared with the existing DVI connector, which is also a digital connector, the biggest change of HDMI is the integration of video and audio transmission, and the connector is small in size, and its flexibility and convenience are more advantageous. The HDMI interface can solve two problems with only one line. The output will greatly simplify the connection of the device and make the desktop more tidy.

III. Distinguishment

The DVI-D connector

The DVI-I connector

As mentioned above, the current DVI connectors are mainly DVI-D and DVI-I connectors, and these two specifications are further divided into "dual link" and "single link". Of the two types, what we usually see is the single-link version. The dual-link version is expensive, so it is usually used in some professional equipment.

Distinguish between different DVI standards

Among the common DVI connectors, the DVI-D connector can only receive digital signals. The connector has only 3 rows and 8 columns with a total of 24 pins, and one of the pins in the upper right corner is empty. Not compatible with analog signals.

The DVI-I connector is compatible with both analog and digital signals. Generally, the graphics card using this connector will have a related conversion connector.

The difference between an 18-pin and a 24-pin DVI connector

In fact, the 18-pin DVI is single-link, while the 24-pin is dual-link. That is to say, the transmission rate of the 18-pin DVI connector is only half of that of the 24-pin, which is 165MHz. The on-screen display, the resolution supported by a single-link DVI connector is exactly the same as that of a dual-link connector, but the refresh rate is only about half of that of a dual-link, which will impair the display quality. Generally speaking, the maximum refresh rate of a single-channel DVI connector can only support 1920*1080*60hz or 1600*1200*60hz, that is, the normal display of the existing 23-inch widescreen monitor and 20-inch normal ratio monitor, if it is higher it will impair the display effect.

IV. Future development

Although the DVI connector is a fully digital transmission technology, at the beginning of its development, its initial goal is to achieve high-definition, lossless compression of digital signal transmission. Because the making of it did not take the trend of IT products and AV products integration into consideration, the DVI standard puts too much emphasis on the support of computer display devices while ignoring the support of AV devices such as digital flat-panel TVs. At the same time, for Hollywood publishers who have been concerned about piracy issues, the DVI connector does not provide the copyright anti-theft function they care about. Therefore, from the final result, although the DVI connector has successfully achieved the goal of lossless HD transmission, the over-specific positioning has also caused the overall performance to lag to a considerable extent. Let's look at the main problems of the DVI connector:

- DVI connector is mainly used in PC, which is generally compatible with flat-panel TVs.

- DVI connector lacks support for image copyright protection.

- DVI connector only supports RGB digital signals in the computer field, and unable to support digital color difference signals.

- The DVI interface only supports 8bit RGB signal transmission, which cannot allow a wide color gamut display terminal to exert its best performance.

- For compatibility reasons, the DVI interface reserves a lot of pins to support analog devices, causing the mouth volume to be large and the efficiency is very low.

- DVI connectors can only transmit image signals, and the support for digital audio signals is completely ignored in consideration.

- Due to the above disadvantages, the DVI connector can no longer better meet the development needs of the entire industry. Therefore, whether it is IT manufacturers, flat-panel TV manufacturers, or many publishers in Hollywood, there is an urgent need for a better connector technology that can meet the future development of the high-definition video industry. It is for these reasons that the HDMI standard has been promoted.