基于3G网络的有限带宽下实时视频传输技术研究

发布时间：2018-06-27 07:54

本文选题：实时视频传输 + 码率动态调整　；参考：《重庆大学》2014年硕士论文

【摘要】：在3G网络中传输实时视频是一种典型的应用。相比于其他业务，视频信息的数据量大，传输之前必须经过压缩。目前最常用的压缩标准为H.264，经过H.264压缩后的视频流可以在3G网络信道上获得较好的传输效果。但是由于3G网络带宽不稳定，且抖动明显，因此，如何根据3G网络带宽变化情况，动态调整H.264码率控制策略，以取得更佳的视频传输效果，获得更好的用户体验，是移动网络视频传输技术中值得研究的一个问题。论文工作围绕实时视频通信中发送端可能获取的网络状态信息，从网络带宽预测的角度来动态调节视频码率，并根据帧的重要程度不同，实施有选择的丢帧策略，以期取得更好的视频传输体验。论文主要开展了以下一些工作： ①分析了实时视频通信中视频发送端可能感知的网络带宽参数，建立一种视频编码码率控制的模型。该模型根据发送端缓冲区比特流的大小，预期的网络带宽和变化趋势，来调整和控制相应的H.264码率控制指标。 ②在以上模型基础上，提出了针对模型中不同处理阶段的优化策略。针对编码码率频繁切换对移动终端带来的处理开销问题，实施码率分等级变换方式；通过设定和监测相关参数阈值，实施发送缓冲区管理策略；根据H.264编码后的帧重要性不同，在3G网络出现拥塞情况时，根据帧的重要性不同而采取优先丢弃非关键帧的帧丢弃策略。 ③采用JM平台和VCEG-N80离线环境，开展了仿真实验，以检验所提出方法在网络带宽预测方面的有效性。通过测量丢包率计算PSNR值的实验，，比较了传统传输模式与论文改进模式下实时视频传输效果的不同，验证了论文所提出改进方法的有效性。
[Abstract]:It is a typical application to transmit real-time video in 3G network. Compared with other services, video information has a large amount of data and must be compressed before it is transmitted. The most commonly used compression standard is H.264. The video stream compressed by H.264 can achieve better transmission effect in 3G network channel. However, because the bandwidth of 3G network is unstable and jitter is obvious, how to dynamically adjust H.264 rate control strategy according to the change of 3G network bandwidth, in order to obtain better video transmission effect and better user experience, It is a problem worth studying in the video transmission technology of mobile network. This paper focuses on the network state information that may be acquired by the sender in real-time video communication, dynamically adjusts the video bit rate from the point of network bandwidth prediction, and implements a selective frame dropping strategy according to the importance of the frame. In order to achieve a better video transmission experience. The main work of this paper is as follows: 1 the network bandwidth parameters that the video sender may perceive in real-time video communication are analyzed and a video coding rate control model is established. The model adjusts and controls the corresponding H.264 rate control index according to the size of the buffer bit stream, the expected network bandwidth and the changing trend. An optimization strategy for different processing stages of the model is proposed. In order to solve the problem of processing overhead brought by frequent code rate switching to mobile terminal, the rate hierarchical transformation is implemented, and the transmission buffer management strategy is implemented by setting and monitoring the threshold of relevant parameters. According to the different importance of H. 264 encoded frame, When there is congestion in 3G network, according to the importance of frame, the strategy of dropping non-key frame first is adopted. 3 the simulation experiment is carried out using JM platform and VCEG-N80 off-line environment. The effectiveness of the proposed method in network bandwidth prediction is verified. Through the experiment of calculating PSNR value by measuring the packet loss rate, the differences between the traditional transmission mode and the improved mode of real-time video transmission are compared, and the effectiveness of the improved method proposed in this paper is verified.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN919.8

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