为了克服在低比特率下的块效应,并适应实时编、解码的需要,提出了一种对残差帧的四叉树编码算法,该算法首先采用OBMC的方法生成预测帧以有效消除块效应,并针对残差帧的统计与视觉特性,对每个2×2的小块取灰度平均值作为最小编码单位,然后用四叉树分解方法来大致标记均值大于某阈值的块的位置,并以标量量化和自适应算术编码器编码其灰度值.与基于变换的编码方法相比,该算法简单、高效,码率低,解码质量高,是一种实时的编、解码算法.

In this paper we propose a novel quadtree decomposition coding algorithm for residual frames in video coding. First we employ overlapped block motion compensation to reduce blocking artifacts, this leads to smoother motion prediction frames which helps to encode the residual frames more efficiently; based on the nature of human visual system, we regard each 2×2 subblock as a basic coding unit, compute its mean value, and use a new quadtree decomposition method to label the subblocks with larger magnitude than a chosen threshold, then code them with scalar quantizer and adaptive arithmetic coder. Compared with transform-based methods, such as EZW and H.263, the proposed algorithm is more efficient and has better performance, which indicates that it is a very effective and computationally simple technique especially for low bit rate coding. Moreover, the coding and decoding procedures are so fast that it can satisfy real-time applications.