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The key technology of oversized indoor LED display screen control system

Tag: oversized indoor LED display screen control system, indoor giant led screen, oversized led display solution, indoor video wall, interior video wall

 

Abstract: In this paper, the key function and performance of oversized indoor LED display screen control system was introduced through a certain LED project in Chengdu, which includes the support for point-to-point chroma revise, automatic fault diagnosis and state detection, synchronization of oversized screen load, backup technology of dual-system redundancy, high intensity and high refresh frequency, etc.

 

indoor giant led screen,interior video wall 

indoor giant led screen

 

>> The control system accounts only for a very small part of the display screen cost, but it plays a very important role in the stability and reliability of the display screen and the improvement of the effect of the display screen.

 

1. The system’s supports for point-to-point chroma revise:

 

>> As an effective means to enhance the image quality of LED display screen, the concept of point- to-point chroma revise was introduced into China since 2007. The completion of the point- to-point chroma revise requires the collaboration of the corrective system and the control system, thereinto the corrective system is responsible for generating the correction coefficient while the control system is responsible for applying the correction coefficient. Since 2007, the control system of a few domestic manufacturers has already begun to support the storage, management, application of correction coefficients and, since 2009, it has been necessary for foreign professional users and most of the domestic high-end projects to have the function of correcting point by point. Point-by-point correction is divided into point-to-point correction of brightness and point-to-point chromaticity correction. Relative to brightness correction, point-by-point chromaticity correction based on the principle of chrominance compensation can obtain higher consistency and less brightness attenuation, therefore, the control system’s support for point –to-point chromaticity correction will become a trend.

 

>> The LED display screen system project in Chengdu, China is an oversized indoor LED screen project, of which the control system accompanied with the latest correction system can conduct a point-to-point color correction, ensuring a high degree of the brightness and chromaticity of each LED.

 

>> Here is a comparison of the point-to-point color correction of a display screen in Shenzhen, in which there is a lot of module that appears in shades of red (especially near the top right part of the picture). In view of the obvious nonuniformity of the color, we can’t obtain good corrective effect if we correct brightness alone. In this case, the color correction was applied, and we can see the remarkable improvement and upgrading of the image quality on the display screen.

 

an area chart of a badly-color-balance display screen before and after correction

Figure 1: an area chart of a badly-color-balance display screen before and after correction

 

2. Automatic fault diagnosis and state detection technology:

 

>> An LED display screen is composed of numerous electronic components (the number of components of a screen is as large as tens of millions or even more). Users need to monitor the working state of display screen, and each trouble that is potential or has occurred. The newest control system mentioned above, which the Chengdu LED display screen system adopted in project, can monitor the state of every link that is easy to go wrong composed of millions and millions of components (including the temperature, humidity, smoke inside every box, the voltage of every switch, the rotate speed of every fan and whether the LED lights are cutting-out or not). The system can automatically deal with emergencies when any faults occur, and automatically send notification to the maintenance personnel via text messages and emails. Automatic fault diagnosis and state detection can greatly improve the maintenance speed, and reduce the operation risk of LED display screen effectively.

 

3. Large screen loading technology:

 

>> For the area of hundreds of square or even thousands of square meters, or more than 1920*1200 screen resolution, requiring several main control can load. Chengdu a LED display system project resolution up to 5440*1200, up to 6500000 pixels, in order to avoid the high speed shutter picture appear different load of bright and dark not synchronization problem, can achieve sub field level synchronization each receiving cards and each main control need. At present most of the control system is to solve the synchronization problem receiving clip field, but most of the control system (including foreign some well-known LED display manufacturers) synchronization problem has not been solved different master. In the use of multiple master when carrying giant screen, between these different main control need to add hard sync signal, so that each of the sub fields are synchronized submicrosecond, can completely solve the synchronization problem. The project adopts the control system, can achieve different main control fully synchronous direct.

 

>> Controller control system adopted in the project can load 2300000 pixels, greatly exceeded the carrying capacity of common control system of single card 1300000 pixels.

 

>> Below is the random shot a two giant display photos, used the 1/800 shutter. The two screens because the area is very large, with multiple sets of main control with load. Figure 2 displays exist between different main control severe load are not synchronous, synchronization between the control system diagram of 3 display master is very good.

 

left: Multiple master camera is not synchronized display            right: Camera multiple master synchronous display

 

>> In addition, the giant screen, also need to use broadcast scheme suitable (because the screen resolution possible maximum output resolution of more than one computer graphics). In this paper, the Chengdu LED display system project, screen resolution can reach 6500000 pixel resolution of 2300000 pixels, far more than a single computer graphics output. In order to ensure the player clarity, play the point of need to play, play the video server of the project, a single independent smooth playback of 10000000 pixels in the video, it can provide up to 24 DVI output, its new technology, can guarantee the synchronization between each of the DVI outputs.

 

4. Redundant technique:

 

>> Redundancy technology is popular in recent years is a single loop, this redundancy technology and low cost (without increasing the system), but in theory, because in the loop if there are two transmission failure will cause the part blank, and in any one of the master or scan board self failure display will appear black.

 

>> There is a redundancy technology in major projects have also been applied, control systems are made redundant backup, which adopts double backup master and scan card. The main control system uses a dual redundancy backup, on a master or a piece of board failure, display screen can display properly. The program cost than the loop redundancy costs doubled, but its stability is greatly improved. Believe that major projects in the future there will be more and more will use the redundancy technology.

 

>> This paper described the Chengdu LED display system project, redundant hot standby technology the new control system is adopted, the system adopts the double signal two master redundancy, failure in a master or a transmission line, the display can work normally; if a receiving card fails, only fault accept card with area of screen, screen body after this card does not appear all black. Compared with double main control double receiving card redundancy backup, saving much cost (just master doubling).

 

5. High intensity high refresh rate:

 

>> Control system using the LED display in the paper uses the most advanced technology, the general drive chip, can achieve higher intensity, more high refresh, 14 bit grayscale scanning screen refresh can reach more than 3000HZ, 16 bit gray static screen to achieve complete, refresh to higher. Greatly improve the LED display pictures.

 

>> The Chengdu LED display system project, using the static screen, can display refresh reached more than 5000, gray is a complete 65536 stage, that is 16 complete gray, can ensure that the camera and camera to achieve very good results.

 

6. Summary:

 

>> This paper described the Chengdu LED display program, control system solution provider offers from player to control, simple and convenient solution. With relatively low cost, achieve stability, ease of use, green energy saving and environmental protection and other aspects of a comprehensive upgrade. Display control system more stable, display effect is more delicate, uniform display significant improvement. The real-time condition monitoring technology enables the display maintenance more quickly.

 

Topology of oversized indoor LED display screen control system

figure is a LED display control system topology described herein

Click to view full size 

 

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