Video Card output interface Overview

The video card is a bridge between the host and the display. After the display signal is processed, the video card must send the signal to the display card through the corresponding interface. The video card interface is used to output the video card.

Video Card interfaces have developed very rapidly in recent years. The development from D-sub and S-video to DVI, hdmi and displayport is just a few years. Now, the video card interfaces on the market are still the mainstay. Which of them have become the stars of tomorrow and what are the stars of the future?

Once King D-SUB

D-SUB interface (also called VGA Interface) was almost the only output interface of the video card, "Occupy" the entire video card market. From the appearance, the D-SUB interface "Up width and down narrow", looks like a inverted "D", this interface is commonly known as the "D Type Header ", the reason for this is that it is easy for users to install-the plug will not be reversed. D-SUB interface has a total of 3 rows of 15-pin signal line, it transmits a analog signal-through the transmission of different voltage signals to control the image display. The video card processes digital signals. To achieve signal output, the display core is integrated with a component named "ramdac" (video storage digital analog converter, it converts the digital display signals processed by the display core and stored in the video memory to analog video signals composed of three types of color brightness and row and frame synchronization signals, finally, the output is to the display through a 15-pin D-D-SUB interface. Due to the limitations of technology and bandwidth, it cannot display larger resolution, image quality is also relatively poor, as the king of D-SUB interface has been the current status of the river, it can only be seen on low-end graphics cards.

Mainstay DVI

Because the digital signal must pass through the ramdac conversion, and the D-SUB interface is easy to be disturbed when the analog signal is transmitted, it will inevitably cause certain signal distortion and affect the display quality. In the current use of digital signal LCD overwhelming time, the use of D-SUB to transmit the display signal is out of date. After the analog signal is sent to the LCD through the D-SUB, the analog signal can be converted into a digital signal that can be recognized by the LCD. As a result, the signal goes through two steps: "Digital to analog" and "analog to digital", which greatly affects the signal quality. The DVI interface is used to solve this problem. The digital signal processed by the video card is directly transmitted to the LCD screen through the DVI interface, which can avoid signal loss and distortion, this ensures the complete reproduction of computer-generated images. A hot swapping monitoring signal is added to the DVI interface standard to implement plug-and-play. DVI interface is mainly divided into two kinds of DVI-D and DVI-I, DVI-D interface can only transmit digital signal, and DVI-I interface can not only transmit digital signal, but also can transmit analog signal. The joint size and pin arrangement of the two interfaces are the same, the only difference lies in the difference in the number of BITs, DVI-I and DVI-D are 24 + 4pin, 24pin design. Comparison of Two DVI interface appearance of current graphics card DVI interface is almost all using DVI-I, only need to connect a DVI-I to D-SUB adapter, you can connect the D-SUB plug. DVI-I to D-SUB adapter but in the market, we can often see that the DVI line has 18 + 4pin and 24 + 4pin these two specifications. Some people say that 18 + 4pin is a simplified version, and the performance is not as good as 24 + 4pin. Others say that some of 24 + 4pin are ground wires, and the actual effect is the same as that of 18 + 4pin. In fact, 18 + 4pin is a single channel DVI, and all Omitted are the digital signals (tmds, transition minimized differential signaling) processed and output by the video card ), therefore, the transmission rate is only half of the 24 + 4 pin. On the screen display, the single channel DVI supports the same resolution as the two channels, but the refresh rate is only about half of the two channels, the display quality may decrease. Generally, single-channel DVI interfaces, the maximum update rate can only be [email = 1920 × 1080 @ 60Hz] 1920 × 1080 @ 60Hz [/Email] or [email = 1600 × 1200 @ 60Hz] 1600 × 1200 @ 60Hz [/Email], generally, we recommend that you use 18 + 4pin DVI data lines for a display of 22 inch or lower, while 24 + 4pin DVI data lines for a display of more than 22 inch to achieve the best display effect. DVI interface classification DVI interface (basically all DVI-I Interface) is now the most mainstream graphics interface, almost all high and low-end graphics card is equipped with DVI interface.

S-video

When a user wants to transmit a video from a computer to a large screen display device such as a TV, in order to enable the computer's video signal to be recognized by television sets, recorders, and other devices, in addition to interfaces D-sub and DVI, some graphics cards with video output functions also provide a video output port, namely the S-video interface. The S-video interface separates the color signal C and Brightness Signal y of the video signal and transmits the signal through different channels, reduce the process of "separation" and "synthesis" during image transmission, reduce the loss in the conversion process, and reduce mutual interference between signals, reduces the interference between brightness and color during video program output to achieve better display effect. For some high-end graphics cards, the S-video interface provided by the system can output computer video signals to other devices, it can also input video signals from television sets, vcdns, video recorders, and other devices into a computer. This function is called "vivo ". With video processing software, you can capture signals from other video devices in real time. S-video can be connected to almost all large screen display devices such as televisions, so although its technology is not advanced, S-video interfaces will still be provided on some high-end graphics cards.

HD pioneer HDMI

HDMI (High-Definition Multimedia Interface) is the same as DVI for transmitting full digital signals. The difference is that the HDMI interface can not only transmit high-definition digital video signals, but also transmit non-compressed full-digital high definition, multi-channel audio and smart format and control command data. The maximum quality of audio and video signal transmission can be ensured because the number of lines/mode conversion or mode/number conversion before signal transmission is not required. You only need one HDMI cable to transmit audio and video signals at the same time, instead of connecting multiple cables. HDMI audio signals do not take up any extra channel. Even when transmitting 1080 p (60Hz) video signals, up to 8 channels can be provided, high-quality audio signals with a sampling rate of kHz each. The HDMI interface uses the same digital video signal transmission mode as DVI. The HDMI interface can be backward compatible with the DVI interface. You only need to use a dedicated transfer cable to convert the HDMI to DVI (lost audio signal) or convert DVI to HDMI (without audio signal ). Due to the high transmission speed, high output resolution, and convenient connection, the HDMI interface is very suitable for HD video output. Currently, many high-end video cards have abandoned S-video and switched to the HDMI interface. In addition, because the HDMI interface outputs digital signals, the attenuation is small, and the quality of the HDMI connection line is good, even up to 15 meters, can output excellent quality.

Futuristic star displayport

Displayport is also a standard for High-Definition Digital Display Interfaces. It not only connects computers and monitors, but also computers and cinemas. Displayport provides up to 10.8 Gbit/s of bandwidth, higher than the 1.3 Gbit/s of the latest HDMI 10.2, and it is free to use, unlike HDMI, which requires a high licensing fee. The displayport interface, like HDMI, also allows communication between audio and video signals using a single cable and supports multiple high-quality digital audio signals. In addition to the four primary transmission channels of displayport, there is also an auxiliary channel with a bandwidth of 1 Mbps, which can be directly used as a transmission channel for low-bandwidth data such as voice and video, it can also be used to control games without latency to integrate and control peripheral devices. Displayport has won the support of AMD, Intel, NVIDIA, and other IT industry giants because it is not only advanced in technology, but also has no patent license fee. The industry also regards the displayport interface as the futuristic star to replace the DVI interface. Currently, a small number of video card manufacturers have tried to provide displayport interfaces in their mid-and high-end video cards.

Tip: a graphics card provides at least one display interface (D-SUB or DVI), that provides both D-SUB and DVI interface or two DVI interface graphics card, also known as "dual-head" graphics card, this type of graphics card can be connected to two monitors at the same time. The S-video and HDMI interfaces are not required. The video card manufacturer determines whether to provide these interfaces on the video card. While the displayport interface is still relatively advanced, although most graphics cards (including integrated graphics cards) currently support displayport output, there are still few graphics cards equipped with the displayport interface.