The Applied Research Of Screen-sharing Technology On Projection System

With the development of computer technology and optimization of screen-sharingrequirements in our daily life, the major manufacturers have introduced TV boxes, TV sticksand other screen-sharing equipment, which can help the computers, mobile phones and othersmall screen computing devices connect with the projectors and other large-screen displaywireless devices within the LAN. For example, home users can use Google Chromecast totransmit video on the phone or tablet device to the smart TV via WIFI. But these Chromecastdevices are confined to a particular hardware platform, and require additional purchase.In the classroom or meeting room where projection display is needed, the projector’sVGA or HDMI cable limit the physical locations of the projection speaker. Besides, there arecompatibility problems with the projectors from different manufacturers. In the classroom oroffice, a majority of people use the Windows operating system, and we need to take fulladvantage of the invested hardware equipment. Therefore, the research of the screen-sharingsystem on Windows operating system will have more display space in the classroom ormeeting room.The processes of sharing a computer screen include screen image acquisition, encodingand decoding, transmission and display. It belongs to the field of streaming media, which hasmany features as large amounts of data, high computational complexity, and high real-timerequirements. When it is applied to the classroom or meeting room projector occasions itrequires high performance screen image acquisition technology, high-performance audio andvideo codec algorithms and processing power of the hardware platform.In this paper, we use Desktop Duplication technique to quickly and efficiently grab thecomputer screen image. Experiments show that the screen capture frame rate is greater than40fps. And it can grab the changing area of computer screen image so that reduce the numberof screen capture.We present a high performance codec model, which divide the screen image into a videoframe and normal frames. We utilize the H.264to codec Video motion frames, and researchthe hardware acceleration of H.264on different hardware platforms. Normal frame is dividedinto text blocks and image blocks. We use YUV444format to sample text blocks, and then use the entropy codec to codec it. It can reduce the distortion of the text block. We use JPEGto codec the images blocks, which avoiding the codec complexity of H.264. Experimentsshow that the coding takes less than22ms, decoding takes less than8ms, CPU occupancy ratetake less than23.2%.In this paper, we design and implement a high-performance computer screen-sharingsystem based on the above model and Windows8operating system. The system display adelay of200ms, and the CPU occupancy rate is less than11.8%, the network usage is lessthan3M, the clarity and fluency is95points (out of100). The result shows that the systemreach the requirements of high-definition, high fluency and low latency.