| Accompanied by the ultra-fast development of mobile communication technology and the considerable growth of mobile data requirement,users enjoy low-latency,high-quality network services while experiencing high-speed data transmission.In particular,wireless video services play a More meaningful role in real-time transmission fields such as security monitoring and remote images with their irreplaceable advantages.However,in the limited bandwidth,the wireless network presents a variable network status due to signal interference,and the burden of high bursts of data make it difficult to ensure the reliability of the transmission link.There are multiple obstacles to providing users with low-latency,high-quality video transmission services.In a word,joint source-channel coding based on wireless networks will be the dominant trend in the evolution of the video transmission industry in the future.Existing research has verified that a video transmission bitrate control strategy based on joint source-channel coding can significantly reduce the loss of effective video data and ensure the provision of high-quality video transmission services under the limited transmission bandwidth.Hence,it is very meaningful to research the real-time video transmission technology of joint source-channel coding.It is found that by matching the time-varying characteristics of the transmission channel by adjusting the video transmission rate can assure the video stream to the client reliably,timely and in high quality.However,the source coding bitrate and the channel coding bitrate have a competitive relationship under limited bandwidth resources,and the insufficient code rate in either aspect may cause different degrees of video distortion.Aiming at the time-varying characteristics of multiple parameters in wireless transmission links,this paper proposes an adaptive bit rate allocation scheme for high-quality video.The solution can dynamically allocate the source code rate and channel code rate dynamically,which not only guarantees the basic video compression quality,but also has a high error recovery capability.In addition,the channel coding length should be reasonably increased according to the type of video frame and the length of the information to ensure that the FEC error correction performance is maximized under the equal redundancy ratio.The simulation results show that,compared with traditional algorithms,the video transmission loss rate and end-to-end delay of the algorithm proposed in this paper are significantly reduced,thereby obtaining a higher PSNR gain.On the other hand,considering that the FEC-based channel coding scheme has strict requirements for redundancy configuration,unreasonable redundancy allocation is likely to lead to a series of problems such as insufficient error correction performance and increased delay.Therefore,this paper combines the three anti-packet loss strategies of FEC,NACK and HARQ,and considers the different performance effects of each strategy in the three aspects of delay,quality and transmission efficiency,and proposes a low-complexity adaptive anti-packet strategy selection algorithm.By establishing a unified system delay model under different link delay performance,different data packet error correction mechanisms are accepted.The experimental results show that the proposed algorithm can dynamically select the optimal anti-packet loss solution,and optimize the data transmission efficiency under the premise of making certain of the video quality.Finally,a video transmission system with joint bitrate allocation is constructed based on the semi-physical simulation equipment is constructed,and the proposed algorithm is verified.The proposed algorithm can run reasonably in real application scenarios,and provides ideas and references for the optimization of real-time video transmission performance and the later actual engineering applications. |
