【作者】 李云峰；

【导师】 彭强；

【作者基本信息】 西南交通大学 ， 计算机应用技术， 2004， 硕士

【摘要】 视频编码是在保证一定重构质量的前提下，以尽量少的比特数来表征视频信息。然而采用预测编码后的视频数据对传输中产生的误码非常敏感。随着不可靠信道视频通信的广泛应用，差错控制与掩盖技术逐渐成为多媒体研究领域的一个热点。交互式差错控制技术是一种视频编解码器相互协作来解决视频传输差错的技术。参考帧选择技术利用先前正确解码的一帧作为参考，从而较好的实现了抑制差错扩散的目的，并且由于它相对原理简单，计算复杂度小，对比特率几乎没有什么影响，无须太多解码端信息，无须修改编码流语法等诸多优点，因此得到了广泛关注。本论文便是围绕着参考帧选择技术及其相关技术进行了详细的研究和试验。 本文的主要内容包括： (1) 在码率受限的信道上实时传输视频数据需要对视频编码进行流控，本文根据视频编码码率控制的基本思想，针对H.26L标准目前没有流控的缺点，基于JVT流控算法对H.26L标准加入流控模块，实现了编码数据流的平滑输出。 (2) 详细分析参考帧选择的两种模式：ACK模式与NACK模式，并对比了两者的性能与适用场合，还根据网络差错状况提出了一种模式切换的机制，以使得系统在任何差错环境下都能达到最佳的差错恢复效果，最后还分析了该技术对编码帧存控制的影响 (3) 利用差错跟踪准确计算编码帧出错受“污染”宏块的思想，将差错跟踪技术与参考帧选择技术相结合，提高编码效率和差错掩盖性能。 (4) 对上述算法在新一代视频编码标准H.26L上实现，试验结果表明，参考帧选择技术能够有效地阻止差错的进一步扩散，大幅度提高因为差错而恶化的视频质量，相信该技术将会在未来的视频通信中有着较好的应用前景。更多还原

【Abstract】 Video coding is a technique of representing video information with as little as possible bits to guarantee reconstructed picture quality. However, the compressed video is sensitive to the network error due to the predicted coding. When the inter frame coding is used in an error prone network, problem arise not only of greater degradation of the erred picture quality due to the errors but also of temporal and spatial propagation of the effects of the errors. The truth of video error control techniques is to make the hurt of transmission errors least whenever and wherever the transmission errors happened. Interactive video error control technique is proposed to remove transmission errors by transmitter and receiver’s working together. Reference picture selection restrict the encoder the correctly decoded picture as the reference picture according to the backward channel signaling to prevent the temporal error propagation.The thesis is mainly concerned about:( 1 ) Rate control plays a very important role in constant bit rate(CBR) coding. In this paper, rate control module is introduced in the H.26L video coding standard based on the idea of rate control about video coding to smooth output of encoding data stream.(2) The reference picture selection system has two modes, one is ACK mode and the NACK mode. We explain both modes and focus on the mode switching mechanism according to the error condition on the network so that the optimal performance can be achieved in any error conditions. We show the performance of several modes and their application condition, finally the influence to the size of memory for reference pictures is analyzed.( 3 ) Error tracking allows the encoder to estimate interframe error propagation accurately, we combine error tracking and reference picture selection to accurately restrict correct reference area to improve encoding efficiency and the performance of error concealment.(4) Realize above arithmetic based new video coding standard H.26L. Simulative experimental results show that reference picture selection prevent effectively the error propagation and improve video quality.更多还原