【作者】 王文答；

【导师】 郝燕玲；

【作者基本信息】 哈尔滨工程大学 ， 导航、制导与控制， 2009， 博士

【摘要】 本课题从不可控网络下的视频传输应用出发,针对在带宽波动情况下为用户提供最优化视频体验这一目标,对比分析了现有各种小波视频编码算法并选定最符合要求的编码框架,在该框架基础上进行编码算法的优化研究,从编码、传输、解码等环节综合考虑给出了动态码率传输控制算法。它能够提高视频应用对网络状况变化的适应能力,提升用户的视频体验。本文提出了一种改进的多帧预测无更新杠铃提升运动补偿时域滤波算法,给出了基于块运动模型的多帧预测快速运动估计方法,在提高编码效率。在该算法中,提出的层次化参考帧集合选择方法充分考虑了时域可伸缩性,能够支持视频传输时的帧率动态调节,为动态码率传输和控制提供了条件。本文在上下文模型嵌入零块编码算法基础上提出了基于位长四叉树和上下文模型的嵌入零块编码算法。该算法继承了上下文模型嵌入零块编码算法编码效率高、质量可伸缩性好等优良特性,同时解决了原算法占用内存较大的问题。小波视频编码算法一般内存消耗较大,因而一定程度上制约其应用,本文提出的改进算法相比原算法节省了编码过程中80%的主要内存消耗,在小波编码算法领域具有通用性,有较大的应用推广价值。本文结合基于位长四叉树和上下文模型的嵌入零块编码算法提出了一种带描述的流打包方法。编码器在编码过程中预先产生对二次码流提取起辅助作用的流描述信息,流媒体服务器通过解析流描述信息即可根据目标码率大小快速完成二次码流的动态提取和分发,并使得该码流接近率失真准则的最优值,因而大大降低了流媒体服务器在二次码流提取时的运算量,该方法在并发用户数高的大规模视频业务系统中具有较高的应用价值。本文在对小波视频编码方案进行优化和改进的基础上提出了一种改进的动态码率传输控制算法,通过编解码算法和传输控制算法的有效结合,大大减少了不可控网络下视频播放过程中出现的停顿、缓冲、中断,视频画面中出现的马赛克、拖影等严重影响用户体验的现象,显著提升用户视频体验。基于本文优化后的小波视频编码方案,流媒体服务器利用本文提出的动态码率传输控制算法可以很方便地进行二次码流提取和分发。与直接将编码器集成到流媒体服务器进行动态码率调整的方案相比,本文提出的方案大大降低了流媒体服务器的性能消耗,适用于大规模的视频业务应用。更多还原

【Abstract】 This dissertation focuses on the video transmission applications under the uncontrollable network. It aims to provide the best video experiences to users in the network environment that the band-width changes frequently. After the contrast analysis on each kind of wavelet video coding algorithm, the most suitable wavelet coding framework is selected and the optimization research is carried based on this framework. The dynamic bit-rate transmission control algorithm is brought forward after evaluating in each process such as coding, transmission, decoding etc. It can enhance the adaptation ability of the video applications when the network environment changes and improve the video experience of users.An improved multi-frame prediction and no update barbell lifting motion compensated temporal filtering algorithm is brought forward and a fast motion estimating method of the multi-frame prediction based on the block motion model is proposed in this dissertation. It can enhance the wavelet video coding efficiency. In this algorithm, the selecting method of the hiberarchical reference frames set has considered fully about the temporal scalability of the video coding. It can support dynamic frame rate adjustment during the video transmission and thus provide the conditions for the dynamic bit rate transmission and control scheme.An improved algorithm based on the Embedded Zero Block Coding and Context Modeling algorithm, Bit Length Quad-tree No List Embedded Zero Block Coding and Context Modeling, is brought forward in this dissertation. This algorithm inherits the good merits such as the high coding efficiency and the good quality scalability from Embedded Zero Block Coding and Context Modeling algorithm. Simultaneously, it has solved the high memory consumption problem of Embedded Zero Block Coding. The wavelet video coding algorithm often consumes a lot of memory in the coding process, thus to some extent restricts its application. The improved algorithm proposed in this dissertation saves about 80% main memory consumption in the coding process in comparison with the original algorithm. It has the versatility in the wavelet coding algorithm domain and has the great value in the applications. A new stream packet method with stream description is brought forward in this dissertation by linking with the Bit Length Quad-tree Not List Embedded Zero Block Coding and Context Modeling algorithm. The encoder produces the stream description information in advance in the coding process. The stream description information can assist the media server to extract the sub-stream as need. The media server can extract the sub-stream and deliver it to the user according to the different bit-rate by using the stream description information as reference and simultaneously make the sub-stream close to the optimum according to the rate distortion criterion. Thus it can greatly reduce the operating complexity when the media server extracts the sub-stream. This method is valuable in the application of large-scale video transmission with large concurrent users.A dynamic bit rate video transmission and control scheme is brought forward in this dissertation. By the effective co-operation between the codec algorithm and the transmission control algorithm, the scheme greatly reduces the phenomena which seriously impairing the video exp eriences of users such as stop, buffering, interrupt, the mosaic and ghost in the pictures while video stream playing under the uncontrollable network. Thus it can improve the video experience of users. Based on the optimized wavelet video coding scheme proposed in this dissertation, the media server can use the dynamic bit rate video transmission and control algorithm proposed in this dissertation to extract sub-stream easily and deliver it to the users conveniently. Comparing with the scheme that the encoders are integrated directly in the media server to carry on the dynamic bit rate adjustment, the scheme proposed in this dissertation can greatly reduce the performance consumption of the media server. Thus it is suitable in the large-scale applications of video transmission.更多还原