Tue Sep 05 16:12:59 CST 2023
DVI's full name: Digital Visual Interface, by the Intel Developer Forum in September 1998, the establishment of the Digital Display Working Group (Digital Display Working Group referred to as DDWG) invented a high-speed transmission of digital signals, DVI interface can be transmitted uncompressed digital video data to the display device.
In 1999, Silicon Image, Intel, Compaq, IBM, HP, NEC, Fujitsu and other companies jointly formed the DDWG launched the interface standard. There are DVI-A, DVI-D and DVI-I three different interface forms, DVI-D only digital interfaces, DVI-I have digital and analogue interfaces, the current application is mainly DVI-I (24 + 5) based.
The protocol of the DVI interface allows the brightness and colour signals of the pixels to be transmitted from the source (e.g. a graphics card) to the display device in binary form. When the display is driven at its native resolution, it simply reads the numeric information for each pixel from DVI and applies it to the correct position. In contrast to the analogue method where the pixel data is affected by neighbouring pixel data, electromagnetic noise and other analogue distortions, in this method, each pixel in the output register corresponds directly to each pixel on the display. This guarantees the basic quality of the image.
The DVI interface is based on Silicon Image's PanalLink interface technology and is based on the TMDS (Transition Minimised Differential Signaling) electronic protocol as the basic electrical connection.TMDS is a differential signalling mechanism that allows pixel data is encoded and transmitted over a serial connection. The digital signals generated by the graphics card are encoded by the transmitter according to the TMDS protocol and sent through the TMDS channel to the receiver, where they are decoded and sent to the digital display device.
A DVI display system consists of a transmitter and a receiver. The transmitter is the source of the signal, which can be built into the graphics card chip or in the form of an additional chip on the graphics card PCB; while the receiver is a piece of circuitry on the display that accepts the digital signal, decodes it and passes it on to the digital display circuitry, through which both, the signal from the graphics card becomes the image on the display.
The DVI connector can contain the digital signals specified in the DVI standard as well as the traditional analogue signals (VGA), which is designed to maintain the versatility of DVI so that different types of screens can share the same cable. There are three types of DVI connectors, depending on their actual function:
DVI-A(12+5)
DVI-A (A=Analog, transmits analogue signals only): It is an analogue signal interface and can only be used to connect to DVI-A or VGA signals.
DVI-D(24+1/18+1)
DVI-D (D=Digital, only transmit digital signals): is a digital signal interface, can only go to connect the DVI-D interface signals, the interface is only 3 rows of 8 columns of a total of 24 pins, which the upper-right corner of a pin is empty. It is not compatible with analogue signals.
DVI-I(24+5/18+5)
DVI-I (I = A+D = Integrated, transmits both digital and analogue signals): consists of two interfaces, DVI-A and DVI-D, which are clearly differentiated by their pin definitions and are compatible with both analogue and digital signals. Compatibility with analogue signals does not mean that the D-Sub interface for analogue signals can be connected to the DVI-I interface, but must be used through a converter, which is usually included with graphics cards that use this interface.
When DVI-I connects to VGA, it acts as a DVI-A, and when DVI-I connects to DVI-D, it acts as a DVI-D only. In addition, a connector that implements a second DVI link is sometimes called a DVI-DL (dual link).
Some newer DVD players, televisions (including HDTVs), and projectors use the so-called "DVI/HDCP" connector, which is identical to DVI in appearance, but transmits data encrypted by the HDCP protocol to prevent illegal copying. Today's computers with DVI-enabled graphics cards can often use these displays for large screens, but since most graphics cards manufactured before 2007 do not support HDCP, they may not be able to play back HDCP-protected video content at the highest possible resolution due to the limitations of the copyright protection technology.
In addition, the analogue pins of the DVI-D are intentionally designed to be shorter than the same pins of the DVI-I to prevent users from mistakenly inserting the DVI-I male connector into the DVI-D female chassis.
DVI-I single channel maximum resolution: 1920x1200, 60Hz;
DVI-I dual-channel maximum resolution: 2560x1600, 60Hz/1920x1200, 120Hz;
DVI-D single-channel maximum resolution: 1920x1200, 60Hz;
DVI-D dual-channel maximum resolution: 2560x1600, 60Hz/1920x1080, 120Hz;
VGA maximum resolution: 2048x1536, 60Hz.
18-pin belongs to the single-channel DVI, the transmission rate is only half of the 24-pin, 165MHz. in the screen display, single-channel DVI supports the same resolution and dual-channel resolution, but the refresh rate is only about half of the dual-channel, which will cause a decline in display quality. Generally speaking, single-channel DVI interface, the maximum refresh rate can only support to 1920 * 1080 * 60hz or 1600 * 1200 * 60hz.
Fast speed: DVI transmits digital signals, digital image information will be transmitted directly to the display device without any conversion, thus reducing the cumbersome conversion process of digital → analogue → digital, greatly saving time, so it is faster, effectively eliminating the phenomenon of dragging, and the use of DVI for data transmission, there is no attenuation of the signal, and the colours are purer and more lifelike.
Picture clarity: DVI interface does not need to carry out these conversions, avoiding the loss of signal, so that the clarity of the image and the details of the performance have been greatly improved.
Support HDCP protocol: DVI interface can support HDCP protocol to protect HD video with copyright.
By HornmicLink_Bob Kuo @230905 16:15