Why use a small spacing LED screen splicer
Time:2018-09-11
Views:379
With the advantages of real seamless joint, high cost performance and outstanding display effect, the small spacing LED display has been increasingly applied in key occasions such as control room, command hall and conference center.
1. Requirements of image splicing processor
As the pixel spacing of LED display is getting smaller, the viewing distance is getting closer. In order to achieve excellent display effect, not only should the LED display itself be refined in image processing and assembly process, but also higher requirements are put forward for the image splicing processor (hereinafter referred to as splicing device) at the front of LED display.
(1) verify synchronization of output to avoid the phenomenon of dissynchronization of splicing pictures;
(2) optimize the image processing algorithm to maintain high definition of the image processed by scaling;
(3) customize the output resolution to deal with the irregular physical resolution of LED display.
2. Splicing processing technology applied to small-spacing LED display
2.1 combination of splicer and small spacing LED display
A key application of splicer is that it can output multi-channel DVI signal, splicing display of multiple screens arranged in matrix to make it a complete display area in logic.
For the LED display screen, we can define the display area driven by an LED controller as an independent LED display screen. The current LED controller USES DVI/HDMI as the signal input interface, and supports the maximum input resolution of 1920 x 1200@60hz, the maximum bandwidth of 165MHz, and the maximum physical resolution of the driven LED display is 1920 x 1200.
With small spacing products LED display area is more and more big, the project of tens of square meters, LED display of physical tend to be more than 1920 x 1200 resolution, namely every piece of very large scale LED display, are driven by a number of LED controller composed of several independent display area, for the application of stitching machine, only need to correspond to the number of the LED controller provides several DVI output interface, and stitching on the whole LED screen for display.
There are several key technologies worth paying attention to in the application of splicer in small spacing LED display:
(1) signal output synchronization
There must be synchronization problem in the multi-channel DVI signal output of splicer.The asynchronous signal is output to the LED display screen, and the image tearing will occur at the splicing place, especially when the high-speed moving image is played.How to ensure the signal output synchronization becomes the key to measure the success or failure of a splicing system.
(2) graphics processing algorithm
We know that the point-to-point image display effect is the best. For the image after minification processing, if only the ordinary graphics processing technology or the general FPGA graphics processing algorithm is adopted, the edges of the image will be jagged, and even the pixel loss will occur, and the brightness of the image will be reduced.However, the high-end image processing chip or the FPGA system using complex graphics processing algorithm will guarantee the display effect of the reduced image to the maximum extent.Therefore, good graphics processing algorithm is a key technology applied in small spacing LED display splicer.
(3) output of non-standard resolution
Small spacing LED displays are pieced together by a matrix of display units of the same specification. Each display unit size and physical resolution are fixed, but the whole large screen is usually not a standard physical resolution.For example, the resolution of the display unit is 128 x 96, which can only spell 1920 x 1152, but not 1920 x 1080.In the joining together of vlsi system, LED display LED controller driven each area may not be the resolution of the standard, this time, the splicing equipment with the output of the non-standard resolution is the key, it can help us to quickly find the right way of joining together, thus the reasonable allocation of resources, effective save LED controller and the use of transmission equipment number.
2.2 application of splicer for small spacing LED display
At present, splicers can be divided into four categories, namely embedded pure hardware architecture, pci-e bus architecture, distributed network architecture, and hybrid architecture.
(1) embedded pure hardware architecture
The whole machine structure is usually use "back + + signal acquisition boards + master plate signal output board" design, signal acquisition boards such as video acquisition, scaling, superposition, format conversion, such as signal processing work, will be processed through the backplane bus signal transmitted to the main control board FPGA signal processing system, realize to control the FPGA configuration through embedded ARM system, communicate with upper PC, data exchange between the system and by signal output board will signal output to the display terminal.
The structure of pure hardware architecture splicer is relatively simple, and system failure is not easy to occur.The acquisition board and output board can be hot-plugged and easily replaced.Multi-channel and multi-format signal acquisition and processing can be realized.The backplane switching technology and output board card unified clock technology ensure the synchronization of multi-channel signal output.The resolution of each DVI output signal can be customized, which conforms to the stitching characteristics of LED display.
Many features make pure hardware architecture quickly become one of the mainstream products in today‘s splicer field.However, since FPGA is adopted as the core image processing unit, the quality of the algorithm determines the processing effect of a splicer, especially the algorithm of image scaling. How to optimize to achieve a clearer display effect has become an important index to judge the product value of pure hardware splicer.
(2) pci-e bus architecture
Usually, the splicer of bus architecture adopts PCIExpress technology, and the data bandwidth can be up to hundreds of Gbps.The host is equipped with high performance CPU and large capacity memory, which can be preloaded with different operating systems (such as 64-bit Windows7) according to different application areas, and can run various applications directly.The splicer is equipped with multiple high-performance graphics output CARDS, each output card has super high internal bandwidth and video memory, and all output images are synchronized to eliminate image tearing between display units.It also has multiple input CARDS, supports multiple signal formats, and can perform image processing on the input signal.
Pci-e bus architecture splicer is a high-performance computer. All the components are based on the most advanced and mature technologies of major hardware manufacturers, such as Intel for CPU, nvidia for graphics card.High and new technologies in all areas of computing can also be quickly integrated.This makes pci-e bus architecture splicer has incomparable advantages in computing speed, image processing and operation mode.
Pci-e bus architecture splicer has very low threshold. For simple applications, an industrial computer and a professional multi-channel output graphics card can be achieved.
On the other hand, how to solve the problem of system stability, how to design an intuitive and powerful control software, how to solve various problems of data transmission under high bus bandwidth, etc., all require a strong research and development team and a solid foundation of funds, as well as experience accumulation.That is to say, the high-end pci-e bus architecture splicer not only needs to meet the most basic applications such as signal acquisition, processing and splicing, but also needs more investment in system stability, software usability and other aspects, so as to make the splicer meet various rigorous application environments.
However, it should be noted that the bus architecture splicer mostly adopts Windows operating system. Once the system is attacked by virus, the system may be paralyzed and the display will be stopped.Moreover, as customized graphics graphics card is adopted, the resolution of each output channel is generally required to conform to VESA(video electronic standard association) standard. Non-standard resolution output cannot be defined, and different resolution of each channel cannot be defined.
(3) distributed network architecture
Distributed network architecture splicer usually adopts node-like hardware structure. Each input and output nodes are separated independently and connected to the central switch through the twisted pair for interactive transmission of data.
Its core is a set of advanced video codec technology, through a variety of signal input nodes, will be collected DVI, VGA, YPbPr, CVBS, 3 g - SDI signal processing and coding, through a dedicated network communication protocol, the transmission of encoded video through the center switch to the output node decoding, and converted to DVI digital signal output to the display terminal.
The synchronization of output nodes becomes the key to the application of this system.One way is to send synchronization code directly through the network to achieve synchronous output of multiple output nodes.However, due to the existence of network error rate, output synchronization will still occur after running this way for some time.Another way is through the SYNC interface is provided for the physical connection will be more than one output node, an output node is chosen as the host, the initiative to send to other output node synchronization code, so that all the output node receives the SYNC signal at the same time, the true frame synchronization output, to ensure that the complete picture, joining together the screen without tearing.
At present, more and more applications of distributed network architecture Mosaic system are being applied. Due to its distributed characteristics, it is convenient for the integrated wiring in the whole building and the centralized management of multiple display terminals in different areas.With the help of advanced visualization software, we can provide users with humanized, visual and comprehensive services.
However, due to limited bandwidth and encoding and decoding technology, the distributed network architecture does not currently support the access of digital DVI signals and HDMI signals with dual links.At the same time, since the coding, processing, decoding, signal synchronous output and other links all require frame cache, there is a gap in real-time between the data and other splicing technologies.In addition, when the number of point pairs needed to be displayed exceeds 1920 x 1200 resolution image (more than two signal input nodes are needed), the resynchronization output of multi-channel synchronous source input signal cannot be guaranteed.
(4) hybrid architecture
Hybrid architecture generally refers to a splicer or splicing system that combines two or more of the above three splicing technologies.
For example, PCI+ hardware backplane bus architecture splicer can realize system control and image processing independently.PCI bus is responsible for system control and operating system in the background;The hardware backplane bus is responsible for image processing of video. The system allows synchronous processing of a large number of high-resolution input signals while maintaining real-time operation performance and optimal image quality at full frame speed while ensuring synchronization of output signals.For important emergency places, the screen can be guaranteed to never be black. Even if the operating system of PCI bus is responsible for failure or virus infection, foreign video images can be displayed at any time through the special backplane graph processing bus.
Through the mixed architecture, the system can be comprehensively applied to make up for deficiencies, which greatly increases the stability of the system.This is also the future development direction of splicing technology, with a wider application space.
3. Application of small spacing LED display
Currently, small-spacing LED displays are widely used, including but not limited to:
· military exercise command system
· public safety display command system
· power dispatch system
· traffic network and aviation monitoring and display system
· production scheduling system for energy industry
· meeting display system for government, enterprises and institutions
· broadcast and TV media display system
· public place information release system
As a new generation of background wall display terminal, the small spacing LED display screen is providing excellent service for key systems in all industries.
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