What is a DVI port?
What is a DVI port? - Table of contents:
The full name of DVI is Digital Visual Interface, It is a video interface standard designed to transmit uncompressed digitized video. Widely used in LCD, digital projectors, and other display devices. The DVI port can send uncompressed digital video data to the display device. This specification is partly compatible with the HDMI standard.
What is a DVI port?
DVI (Digital Visual Interface), that is, digital video interface. The DVI port is a technology for high-speed transmission of digital signals invented by the Digital Display Working Group (DDWG) established on the Intel Developer Forum in September 1998.
DVI is based on TMDS (Transition Minimized Differential Signaling) technology to transmit digital signals. TMDS uses an advanced coding algorithm to encode 8bit data (each primary color signal in R, G, B) into 10bit data (including line and field synchronization information, clock information, data DE, error correction, etc.) through the minimum conversion, after DC balance Finally, the differential signal is used to transmit data. Compared with LVDS and TTL, it has better electromagnetic compatibility performance and can use low-cost special cables to achieve long-distance, high-quality digital signal transmission.
Digital Visual Interface (DVI) is an international open interface standard, widely used in PC, DVDs, high-definition television (HDTV), high-definition projectors, and other equipment.
DVI has three different types of interface forms: DVI-A, DVI-D, and DVI-I. DVI-D only has a digital interface, and DVI-I has a digital and analog interface, and the application is mainly based on DVI-D (24+1).
DVI port classification
In addition to the digital signal pins specified by the DVI standard, the DVI connector can also include traditional analog signal (VGA) pins. This design is to maintain the versatility of DVI so that different forms of displays can share the same connection line.
According to different functions, DVI connectors are divided into three types and five specifications.
1. DVI-Digital (DVI-D)
DVI-Digital (DVI-D) interface (18+1 and 24+1) is a purely digital interface that can only transmit digital signals and is not compatible with analog signals. So, the DVI-D socket has 18 or 24 digital pin jacks + 1 flat jack.
2. DVI-Analog (DVI-A)
DVI-Analog (DVI-A) interface (12+5) only transmits analog signals, which is essentially the VGA analog transmission interface specification. When connecting the analog signal D-Sub connector to the DVI-I socket of the graphics card, a conversion connector must be used. The conversion connector is connected to the plug of the graphics card, which is the DVI-A interface. This plug can also be seen on early large-screen professional CRTs.
3. DVI-Integrated (DVI-I)
DVI-Integrated (DVI-I) interface (18+5 and 24+5) is compatible with digital and analog interfaces, so the DVI-I socket has 18 or 24 digital pin jacks + 5 analogs The pin jack (that is, the four-pin hole and a cross flower next to it). The 4 more wires than DVI-D are used for compatibility with traditional VGA analog signals. Based on this structure, the DVI-I socket can insert DVI-I and DVI-D plugs, while the DVI-D socket can only insert DVI-D plugs.
DVI-I compatible analog interface does not mean that the analog signal interface D-Sub plug can be directly connected to the DVI-I socket, it must be connected through a conversion joint. Generally, graphics cards using this interface will have related adapters.
Considering compatibility issues, graphics cards generally use a DVI-I interface, so that they can be connected to a common VGA interface through an adapter. Touchscreen monitor with two DVI ports generally use the DVI-D type. For a display with a DVI port and a VGA interface, the DVI port generally uses a DVI-I interface with an analog signal.
5. specifications include DVI-A (12+5), single link DVI-D (18+1), dual-link DVI-D (24+1), single link DVI-I (18+5), dual-link DVI -I (24+5).
The DVI port is divided into two ways of single link (Single Link) and dual-link (Dual Link) when transmitting digital signals. The transmission rate of the single connection DVI port is only half of that of the double connection, which is 165MHz/s, and the maximum resolution and refresh rate can only support 1920×1200, 60hz. As for the dual-link DVI port, it supports up to 2560×1600, 60Hz mode, and can also support 1920×1080, 120Hz mode.
To achieve 3D effects, LCD monitors must have a refresh rate of 120Hz, so in the 3D solution, if DVI is used, a DVI cable with a dual-connection DVI port must be used. In general, if the resolution is within 1920×1200, the output quality of both single and dual connections is the same.
Advantages of the DVI port
1. Fast speed: DVI transmits digital signals, and the digital image information will be directly transmitted to the display device without any conversion, thus reducing the cumbersome conversion process of digital→analog→digital and greatly saving time, so It is faster, effectively eliminating the phenomenon of smear, and uses DVI for data transmission, the signal is not attenuated, and the color is purer and more realistic.
2. clear picture: The internal transmission of the computer is a binary digital signal. If you use the VGA interface to connect to the LCD display, you need to first convert the signal into R, G, and B three primary color signals through the D/A (digital/analog) converter in the graphics card. And horizontal and vertical synchronization signals, these signals are transmitted to the liquid crystal through the analog signal line, and the corresponding A/D (analog/digital) converter is required to convert the analog signal into a digital signal again to display the 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 or even display errors, but the DVI port does not need to perform these conversions, avoiding signal loss, making Image clarity and detail expression have been greatly improved.
3. Support HDCP protocol: The DVI port can support HDCP protocol, laying the foundation for watching a high-definition video with copyright in the future.