Research On Wireless Video Transmission Technology

With the rapid development of mobile internet and popularity of smart terminals, especially in the4G era, it is possible to play the mobile high definition video. More and more people want to quickly access high quality video resources via a wireless terminal. As an indispensable key technology to solve above problems, wireless video compression and transmission technology is becoming the focus in the field of mobile video. Current mobile video suffers from two limitations:scalability and robustness. To solve these problems, we need technological development and innovation.This paper conducts a deep study on wireless video compression and transmission technology.The main contents are as follows:First, the traditional video codec technology represented by H.264is researched. Traditional video coding uses H.264/AVC codec scheme. In order to meet the needs of different bit rates and quality, it extends to the Scalable Video Coding (SVC), which achieves a layered codec idea. Generally speaking, in the case of unicast channel, if channel statistical information is known or priori for the transmitter, the separation of source coding and channel coding is ideal. However, it is difficult to predict the statistics channel in the multicast or broadcast, such a hierarchical design becomes very inefficient, because interference and channel have diversity changes in time and space.Second, the new video codec technology based on SoftCast is studied. SoftCast follows the idea of "cross-layer" design, combines video compression and error protection, and uses Joint Source Channel Coding (JSCC). In SoftCast, video sequence is firstly disposed by DCT transformation, and then uses the real number domain coding to ensure the linear correlation between the transmission value and the original value. The key attribute of SoftCast is that its conversion is linear, which assures that the quality of decoded video for each receiver is proportional to the quality of specific instantaneous channel.Third, SoftCast’s codec simulation system is designed, and compared with the performance of H.264codec system. Using Matlab to set up the video codec simulation system, the paper compares the received video quality of different schemes through the Peak Signal to Noise Ratio (PSNR). The simulation results show that compared with traditional coding, SoftCast using the Joint Source Channel Coding (JSCC) scheme improves3-5dB on the performance, eliminates the "cliff effect", enhances the video robustness and obtaines better video quality and user experience.Fourth, the quality of videos by optimizing the main parameters of SoftCast is improved. The paper respectively studies three main parameters which affect the video quality. They are video block size, video compression and video GoP frame number. The performance of the system is improved significantly by optimizing them.