At present, there are two types of display screen transmission modes according to data: one is to use the timely video screen that displays the same content with the computer; The other is the independent video source display screen that sends the display content to the display screen through USB, Ethernet and other communication means. The wireless communication mode is adopted, and the display content can be updated at any time, with high dexterity. Using an embedded system instead of a computer to supply the video source can not only reduce the cost, but also have high feasibility and dexterity, and it is easy for engineering construction. Therefore, the demand for independent video source LED display systems is increasing.
The system adopts the architecture of arm + FPGA and makes full use of the super processing ability and rich interfaces of the arm to realize real network remote operation. Therefore, it can not only be used as a general LED display controller, but also can form a large outdoor advertising media network with various display nodes. FPGA is a particularly smart programmable logic device, which can be programmed and configured like software, and then can be timely and conveniently corrected and developed, which improves the system efficiency.
1. Independent video LED display control system
The main performance indicators of the LED display screens include field scanning frequency, resolution, gray level, and brightness. Resolution refers to the number of LED tubes that can be controlled by the controller, and gray level refers to the resolution of color. High brightness requires a long and obvious display time for each gray level. These three indicators will greatly reduce the field scanning frequency, so it is necessary to discard these indicators on different occasions. As usual, the gray level, brightness, and field scanning frequency are determined by a single controller, and the resolution can be greatly improved by the display of the controller. In this way, the grayscale and brightness of each controller are very good, and the field scanning frequency is also suitable. After the controller is displayed, a large control area can be realized, and a full-color super large screen LED display controller with fine colors can be realized.
The independent video-led system leaves the control of the computer intact and can realize the functions of communication, video playback, data distribution, scanning control, etc. In order to realize a large screen, full color, and high field frequency, the system adopts the controller display mode.
The system can update the local data from the network server through the network interface (Ethernet interface), and the video playback part decodes the data to obtain the video stream in RGB format. Then, the data is sent to different LED display controllers through the data distribution unit, and the controller displays the data provided by the playback unit on the full-color large-screen LED.
2. LED display control system communication interface and video playback unit
The communication interface and video playing part of the system are realized by arm = uClinux. Arm (Advanced RISC Machine) is a general 32-bit RISC micro-processing system structure designed and developed by British arm enterprises. The design goal is to realize a microprocessor with low power consumption and high performance. As a stable and efficient open-source operating system, Linux has been widely used in various fields. Linux is a Linux system specially designed for the micro control field. It has the advantages of being able to be eliminated, small kernel, perfect network interface, excellent file system, and abundant open source resources, and is being adopted by more and more embedded systems.
The data played by the system comes from the SD memory card (secure digital memory card) in the system There are two ways to update the number of SD cards: one is to update the data of the SD card with a computer; The other is to receive the data from the server through the network and directly update the SD card by arm. Other players can also directly play MPEG-4 format data transmitted through the network. Because Xscale does not provide a physical layer interface, if you want to realize network functions, you need to connect a physical layer chip. The system adopts the high-performance 100M Ethernet controller lan9118 of SMSC enterprise
3. LED display control system video data distribution
Because the controller adopts the display mode, it needs to distribute the data supplied by the video source and correctly send the data of different queues to different controllers.
From the development of LED display technology so far, led full-color display will show ten major development trends: screen oversize, high purity and high density, energy saving, intelligence, light and thin, point-by-point calibration and normalization, indoor screen outdoor, integration of decorative landscape and display screen, and screen enterprise lighting.
The rise and development of full-color LED display screens provides the basis and appeal for the screen’s super size. At present, in order to attract the attention of more advertising owners and audiences, some specific markets, such as large-scale advertising business circles and large amusement venues, vigorously build large-scale LED displays.
High definition and high density are the development trend of the full-color screen display. In order to obtain a better viewing effect, people require the display screen to be from simple full-color to lifelike, restore the authenticity of color, and at the same time, realize the comfortable and clear image display like TV on a smaller display screen. Therefore, the high-definition display screen represented by the high-density and small spacing LED display screen will be the development trend in the future.
Energy saving is the direction in which any industry in China is striving. Led full-color screen involves the use of electricity and operating costs, so energy saving is related to the interests of LED full-color screen operators and the use of national energy. From the current situation, the energy-saving display screen will not increase too much cost than the conventional display screen, and it will save cost in later use, which is highly praised by the market. As an energy-saving LED display screen, it must be a comprehensive result under a variety of indicators. The highlight LED lamp, driving IC, switching power supply, product power consumption design, intelligent energy-saving system design, and structural energy-saving design are related to the energy-saving effect. Therefore, the realization of the energy-saving goal requires the joint efforts of the whole industry.
Like energy saving, intelligence is also the product of LED full-color screen development to a certain stage. The intelligence of the LED full-color screen is reflected in the cooperation between the display screen and the intelligent operation. For example, the brand-new advertising mode of interactive games with pedestrians on the subway advertising screen started at the end of last year.
Point-by-point calibration normalization
In order to meet the needs of modern society, the LED full-color screen works hard on the internal quality of the product on the one hand, and on the external form such as the appearance, volume, and weight of the product on the other. The light and the thin full-color screen are not only conducive to the installation and maintenance of the products, but also reduce the load on the supporting building objects, make it safer, and increase the aesthetics.
Outdoor indoor screen
With more and more projects of indoor and outdoor LED full-color screens, displays of different quality begin to appear in people’s vision. In contrast, the display screen without point-by-point correction obviously cannot meet the needs of the owner and the attention of the audience. The technology of point-by-point correction is maturing and the price is falling. This beneficial technology makes the display effect of LED full-color screen more outstanding. In the future, the point-by-point correction will become the normal technology for full-color screens.
LED display control system has three major components
LED Display Control System (LED Display Control System), which is a system to control the correct display of LED large screen according to the user’s demand, is divided into two categories according to the networking mode: networking version and stand-alone version. The networked version, also known as the LED information release control system, can control each LED terminal through the cloud system. The stand-alone version is also known as the LED display controller, or LED display control card, it is the core component of the LED display, mainly responsible for the external video input signal or multimedia files on board into LED screen easy to identify the digital signal, so as to light up the LED screen equipment, which is similar to the graphics card in the home PC, the difference is that the PC display for CRT/LCD, etc. In this system, the display is an LED screen. LED display control system is mainly composed of control software, program transmitter, and program editor. The specific role of each part is detailed below.
1. LED control software
Easy to operate: flexible and convenient to use, designed for LED large screen production of various playback programs, integrated with a variety of media objects, in the process of program production, you can observe the display effect in real-time, the changes made, will also be reflected immediately to the window. Playback flexibility: the perfect combination of excellent video processing and multimedia network technology, with a good human-machine interface. It is possible to make VGA images and videos appear on the screen at the same time. Multiple editing forms: Input text, images, and other information through different input methods such as keyboard, mouse, and scanner, and edit the inputted content arbitrarily to achieve the desired effect. Displayable stunts: The software can display various text and images on the screen in a vivid and lively form with various stunts such as moving, rolling, pulling curtains, shifting, blinds, zooming in and out, etc. Full control of the playback process: Playback can jump to any program at any time, either at normal speed or fast, or single-step, and during playback is the ability to pause playback at any time, and then restart from the pause. Playable sound effects: the playback software supports synchronous output of sound and 2D and 3D animation
2. The program transmitter uses a control computer to edit and then send graphics generated by the following devices or software to the screen in real-time
The graphics are captured and edited using peripheral devices such as scanners and video recorders, and then sent to the top of the control computer for editing and playback using the control computer. Images have 16 levels of grayscale and can be played back in real-time TV text, video and images can be easily iterated. Stepless zoom in and out of the text, video, and images allows you to operate as you wish using two-dimensional, three-dimensional animation software to create satisfactory animation graphics, and real-time playback on the screen.
3. Program Editor Graphic Editor
Can use WINDOWS within the brush to draw, zoom in, zoom out, rotate, delete, copy, transfer, add, modify, and other means of production of bitmap files to achieve the effect of graphics playback. Text editor: and CCDOS, XSDOS, UCDOS, and other input methods compatible with the text graphics editing software, with imitation, black, regular, Song and its variants of twelve types of font, font size from 128 × 128 to 16 × 16 dot matrix and the size of more than a dozen specifications freely set. And with a variety of decorative words (hollow, tilt, shadow, grid, three-dimensional, etc.), and can be copied, moved, deleted, and other functions of the text. LED display control systems through their own components and construction, with LED display product features, play a brilliant high-definition picture, advertising effect is remarkable, and therefore favored by outdoor media advertisers, businesses, etc. I believe that with the progress of technology and media development, the role of LED display will become greater and greater, and the market is also more extensive.