Introduction to Touch Screen Wireless Video Transmission Technology

There is a wireless video transmission technology in the multimedia conference room system. This technology is realized by a wireless touch screen, that is, a video signal is displayed on the wireless control terminal, so that the wireless touch screen not only has the function of a control platform, but also can display monitoring images, making the touch screen more fashionable.

　　Wireless video transmission technology seems simple, but it has great difficulties, especially when applied to touch screens. Wireless channel bandwidth resources are limited, there are many interference factors, and the video signal data volume is large, and the real-time requirements are high. Therefore, the research on wireless video transmission technology has aroused widespread interest among scholars at home and abroad. The main difficulties in realizing wireless video transmission technology in touch screens are: video compression coding technology and video coding real-time technology, in addition to bit rate control to ensure the stability and high fidelity of the video picture.

　　1. Video compression coding technology

　　The amount of video information is staggering. To transmit it on a wireless network with limited bandwidth, it must be compressed and encoded. At present, there are two major international standardization organizations - ITU-T and MPEG - that specialize in studying video encoding methods and are responsible for establishing fair and unified standards to facilitate interoperability among various video products. These protocols bring together the best achievements of academia. In addition to various encoding technologies based on international standards, there are also many new technologies that are very eye-catching.

　　2. Research on real-time video coding

　　Due to the particularity of video data, the video transmission system has very high requirements for real-time performance. Here we focus on the real-time issues based on video coding protocol algorithms. Although algorithms such as wavelet coding have many advantages, the algorithm complexity is too high and it is currently difficult to meet real-time requirements. The following introduces several important links in the protocol-based coding algorithm, which play an important role in improving the real-time performance of the video coding system.

　　3. Bit rate control research

　　Coding strategy is an important part of the encoder. Bit rate control technology is one of the key technologies in video communication applications. It is responsible for the coordination between each link of the encoder and the transmission channel and decoder, and plays an important role in the encoder. Because the bit rate control strategy needs to be determined by the specific application scenario, video encoding protocols such as H.263+ and MPEG-4 do not specify specific bit rate control methods.

　　Since the structure of video bitstream is layered, the research on rate control scheme is generally divided into two layers, namely, image layer rate control and macroblock layer rate control. The main task of image layer rate control is to determine the expected number of output bits of a frame of image before encoding it, based on the system's expectation of the encoder output bit rate, the system transmission delay limit, and the overflow level of the transmission buffer; the main task of macroblock layer rate control is to select appropriate quantization steps for each part of the image based on the expected number of output bits of the frame of image determined by image layer rate control. The main basis of macroblock layer rate control is the rate-distortion model.