H.264变换和量化的分析

Analysis of transform and quantization in H.264

为了降低运算复杂度和避免解码端的失配问题,通过分析4×4点离散余弦变换(DCT)原理,推导得到H.264标准中第一级4×4点整数变换方法.在该变换的基础上还可以对直流系数再采用第二级变换,进一步消除相关性.与4×4点DCT相比,这种变换方法不但具有DCT去除空间域信号相关性的特点和整数变换的优点,还能够达到类似于DCT的压缩效果.通过分析与整数变换相关的量化过程发现,H.264中的整数变换和量化相结合,计算复杂度低且能获得较以往标准更好的编码性能.

Integer transform can reduce computational complexity and avoid occurrence of decoder mismatch. The first 4×4 integer transform in H.264 was deduced by analyzing 4×4 discrete cosine transform (DCT). In some coding modes, a second transform can be employed on the DC transformed coefficients based on the first one to reduce the correlation. Compared with 4×4 DCT, this new transform method has both the spatial correlation eliminating characteristic of DCT and all the advantages of integer transform. Also, it can gain similar compression effect as DCT. The combination of transform and quantization has low computational complexity and makes H.264 a more effective video coding standard than any other ones before.