I. Introduction
In hybrid video coding standards, such as H.264/Advanced Video Coding (AVC), Audio Video Coding standard (AVS), and High Efficiency Video Coding (HEVC) [1]–[3], Discrete Cosine Transform (DCT) coefficients are first quantized and then losslessly encoded by entropy coding, such as context adaptive variable length coding (CAVLC) or context adaptive binary arithmetic coding (CABAC). Quantization plays an important role in video coding rate-distortion (RD) performance; it not only determines quantization distortion, but also impacts dramatically on the coding rate. The standards, however, define only the inverse quantization, leaving how to actually quantize DCT coefficients to the hands of each video codec manufacture [5]–[7].