【作者】 朱振博；

【导师】 戴琼海；

【作者基本信息】 清华大学 ， 控制科学与工程， 2006， 硕士

【摘要】 在无线视频应用中,无线信道所具有的高误码率,突发差错以及低有效带宽的特性,对视频服务所必须的良好的源到端的QoS保证提出了很大的挑战;而在实时系统中,对网络重传的严格限制则使得这一问题变得更加突出。在这种情况下,已有的研究结果表明,视频编码的差错规避技术将成为解决这一视频服务系统差错控制问题的最有效技术,而如何有效的利用差错规避策略,则成为了当前无线实时视频系统差错控制研究的热点。在本文中,我们将结合目前最新的视频编码标准H.264标准,对无线视频传输中的差错规避算法进行研究。在对无线实时视频服务系统中差错规避技术关键问题的分析之后,我们首先提出使用周期性SP编码帧进行实时视频的差错规避传输的实现方法与框架。在这项技术中,通过周期性的使用SP编码帧,以及对SP编码帧的双参考帧选择与Long-term/short-term参考帧选择算法的结合,可以利用很小的代价,实现视频编码参考链的冗余,从而从根本上防止了视频差错传播的问题。随后,本文针对使用Long-term参考帧的SP编码帧可能由于信道差错率的突然增加而致使参考链被拉长,从而引起码率升高,并且低频R-D性能下降明显的问题,提出在视频编码中,通过在周期性的P帧中加入SP模式编码宏块的方法,有效地改善了算法的码率。在这种方法中,本文通过对H.264编码算法中Rate-Distortion(R-D)模型的改进,有效提出了基于预测模型的包含SP模式的R-D优化编码模式选择算法,并使得这种算法可以方便的融合进原有H.264视频编码算法标准中,并可以有效改善差错信道下视频传输的差错传播的问题。最后,本文针对使用SP编码模式进行实时视频差错规避传输的算法实现进行了初步讨论。特别是其内存管理的设计与H.264编码算法的改进。更多还原

【Abstract】 The high bit error and burst error of the wireless channel are the important challenge for a good meida service deliver over wreless environment. For a real-time media application over wireless, the strict restrict of the packet retransmission makes the chanllenge more significant. In this case, the existing research conclusion shows that a well-designed error resilience technology can supply effective guarantee for the QoS of the media real-time service. And how to design the error resilience system has become the hot area of the error-control research.In our paper, we study the key skill of the existing error resilience technology with the new video encoding standard, the H.264 standard. And, we suggest a novel error resilience method using the period SP coded frame. In this method, period SP coded frames are used to stop the error propagation. The carefully selected of the Long-term/short-term reference frames for the SP coded frames can take an adaptive error control with a low overhead.After that, we find that our method may get a high encoding bit-rate when the error rate is much high in the wireless channel, and it has bad R-D performance in the very low bit-rate application. Our paper suggests an improved error resilience method based on the period SP coded macroblock aming these problems。We improve the Rate-Distortion Optimization Model in the Mode Decision, and suggest a new Rate-Distortion Optimization methord which can decide the SP/P macroblock encoding mode automaticly.At last, this paper concludes the principles and hints for the full optimized streaming application over DSP, and gives the analysis and skills about the implemention of our method on DSP platform.更多还原