分布式视频编码虚拟依赖信道模型研究

Research of the Virtual Dependency Channel in Distributed Video Coding

视频信息固有的非平稳特性,如冲突区域等,使时域预测技术变得非常复杂.在分布式视频编码(DVC)中,由于解码端不能获取当前编码帧的信息,精确地对时域相关噪声进行建模变得更为困难.文中以虚拟依赖信道模型为切入点对如何降低时域相关噪声进行了研究.首先对DVC虚拟依赖信道进行了建模,并对影响边信息的主要因素进行了分析,分析结果表明在变换域中不同的频率子带对时域相关噪声的敏感度不同.在此基础上提出了一种新的基于小波变换域的虚拟依赖信道模型VCMDWT,基于分类编码的思想对较为平稳的LL子带进行Wyner-Ziv编码,对非平稳的高频子带进行SPIHT帧内编码.实验结果表明,与基于像素域的方法相比,所提出的VCMDWT模型能够得到更稳定的虚拟信道,提高DVC系统的率失真性能达到2.6dBs以上.

The inherent non-stationary characteristic of video signal, such as occlusion phenomena, leads to a complicated motion-compensated prediction technology. In distributed video coding （DVC） because the decoder cannot have access to the current frame, modeling the temporal correlation noise becomes a difficult task. In order to reduce the performance degradation owing to the non-stationary characteristic of video signal, this paper focuses on the research of virtual dependency channel model. Based on a common DVC codec, this paper presents a generalized model of the virtual dependency channel, analysis of which shows that in transformation domain the different subbands have various degree of sensitivity to the temporal correlation noise. According to the analysis this paper proposes a novel VCMDWT model, in which the virtual dependency channel is modeled at the LL subband with property of being more stationary, at the same time the non-stationary high frequency subbans are encoded by SPIHT with intra mode. The simulation results show that the proposed model is especially adaptable to the frames with many occlusion areas, which would be unfit for the pixel domain DVC, and finally improves the rate distortion performance with a gain up to 2.6dBs.