Design And Implementation Of Audio And Video Synchronously Transmitted Full-color LED Large Screen Sending Card

With the rapid development of multimedia technology, the display effect of the display terminal is required to be high quality, developing towards large-area, multi-color, high-brightness and high-resolution. A reliable medium for long-distance transmission of multimedia information is provided by the rapid spread of the network technology. LED display technology is promoted by the appearance of ultra-high brightness blue LED, making it to be an effective way to meet the requirement of colorful high brightness large screen display. Recent years, the application range of LED large screen is becoming more and more broaden, and the market demand is growing year by year.LED large screen display technology is a collection of photovoltaic technology, computer application technology and control technology. The entire LED large screen display system contains a control computer, a sending card, several reception cards and the screen. Under the usage of LED large screen to display full-color dynamic real-time image information, the data processing and transfer performance of the sending card needs to match the amount of the data needed to transfer. The expanding display resolution makes it more necessary to improve the performance of sending card. In addition, under the multimedia display and using the recent sending card, an independent line is needed to transmit audio information, which increases costs and wiring complexity. Therefore, an effective way is needed to be found to transmit the audio and video information synchronously with multiplex link.Firstly, operational principle of sending card of LED large screen was analyzed, processing procedure to each frame image was explored; then, the communication protocol of existing sending card was analyzed, on account of its defects, a new communication protocol was designed, by using Gigabit Ethernet and virtual multi-channel technology, audio and video information can be transmitted synchronously, the parameters of receiving cards can be real-time configured, data adaptive recognition; after that, the difficulty to realize this new communication protocol was analyzed, including multi-channel priority arbitration and bandwidth allocation, and the strategy to solve these problems was propounded; finally, the hardware design and FPGA programming were discussed, thus, the implementation of audio and video information synchronously transmitted LED large screen sending card has been accomplished. With optimized FPGA program, the operating frequency reached150MHz, an efficient data processing and transmitting rate was achieved on low-cost FPGA. In this design, audio and video are transmitted synchronized on single cable. By configuring the parameters of receiving cards, it is easy to adjust the display. Benefiting from supporting data adaptive recognition, the data processing method was changed from active interception to passive receiver, data attribution was determined entirely by the sending card, the program of all the receiving cards is identical, so that, system control flexibility is increased, system reliability is improved, and maintenance costs are reduced.