Basic knowledge of VGA signal and VGA matrix

Background:
VGA signal transmission is a hot topic in video signal transmission recently. Various transmission methods have attracted the attention of many engineering companies, and various publicity has also blurred the normal judgment of engineering companies. Here is a brief discussion on the development and principles of VGA transmission.
Overview:
The general VGA display card system mainly consists of three parts: control circuit, display buffer area and video BIOS program. The control circuit mainly completes functions such as timing generation, display buffer data operation, main clock selection and D/A conversion; the display buffer provides display data cache space; the video BIOS is solidified in the ROM of the display card as a control program.
Concept:
First, let’s learn about VGA. VGA (Video Graphics Array) is a video transmission standard launched by IBM with the PS/2 machine in 1987. It has the advantages of high resolution, fast display rate, rich colors, etc., and has been widely used in the field of color displays. At present, the application of VGA technology is mainly based on computers, notebooks and other devices with VGA display cards. However, the application of VGA technology is rarely seen on some devices that require the display of color high-resolution images without the need to use a computer.
The implementation method of VGA display is studied. The embedded VGA display system based on this design method can display and control VGA images without using a VGA display card and computer. The system has the advantages of low cost, simple structure, and flexible application. It can be widely used in advertising and prompt information display in public places such as supermarkets, stations, and airports. It can also be used in operating information display in the production process of factory workshops. It can also be used in daily life in the form of multimedia.
VGA interface DB15 pin signal definition:
Pin Definition
1 Red base color red
2 Green base color green
3 Blue base color blue
4 Address code ID
5 Self-test
6 红地
7 Green space
8                                                               9 Reserved (each company’s definition is different)
10 Digital Place
11 Address code
12 Address code
13 Row synchronization
14 Field synchronization

15 Address code (each company has different definitions)

VGA matrix switcher principle:
The concept of matrix refers to the concept of linear algebra in advanced mathematics. It generally refers to the multiple output options in the case of multiple inputs, forming the matrix structure in the figure below. Each output can be "short-circuited" with different input signals. Each output can only be connected to a certain input, but a certain input can be connected to different outputs (at the same time).
VGA matrix output signal transmission:
VGA signals include R/G/B/H/V, which are three primary colors and horizontal and vertical synchronization signals. Although the VGA cable contains 15 wires, there are only 5 wires in the VGA cable that actually transmit image signals. Therefore, to see whether the VGA cable is good or not, first look at the core quality of the five wires used to transmit RGBHV.
Although the VGA wire core is very small and has relatively large attenuation, there is basically no problem with VGA wire during short-distance transmission. In the early days, in order to solve the problem of long transmission distance, the diameter of the wire core was generally increased and the copper core was made very thick. However, when the transmission distance is long, the problem of crosstalk between the five signals in the VGA cable becomes serious. At the same time, it is extremely difficult to route thick VGA cables in a more complex environment. The VGA cable is easy to break when turning, and there are many other problems (such as external interference, poor solder joints, etc.).
In order to solve the problem of VGA video transmission in the project, the development of VGA video transmission in chronological order is: (VGA cable + VGA amplifier) → (RGB cable + RGB long-line driver) → (twisted pair + twisted pair transmission equipment)

We use this equipment on different occasions. For example, in the studio, we use this converter to input the screen of the scoring software in the variety show to the digital switcher, and at the same time send the analog composite signal to the large-screen display on site. The production director can easily switch the live scoring situation directly to the TV audience through the switcher. With this kind of real-time broadcast, the TV audience can clearly see the same picture as the live audience. This effect is much better than the traditional use of cameras to capture live screen images. In the process of producing relevant financial, stock and other columns, a large number of charts, graphics and text information need to be displayed. By adjusting the relevant indicators of the VGA to video converter, the images we are used to seeing on computer monitors can be reproduced very clearly on TV.

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