Advanced Macro-block Entropy Coding in H.264

Abstract

Existing video encoders, such as MPEG4, H.263 and H.264, adopt variable length coding (VLC) as entropy coding method, focusing on residue data coding. In low bit-rate video coding, larger quantization parameters are used to give a smaller number of bits spent on residue data. As a result, the header overhead is a dominant factor of yielding the overall bit rates. In this paper, macro-block (MB) header behavior is investigated. It is found that the relative percentage of the number of bits of MB header increases with quantization parameter (QP) and header correlation between neighboring MBs is high. Based on these MB header properties, we propose an advanced coding algorithm for entropy coding of MB header. The experimental results suggest that our proposed algorithm achieves lower total number of encoded bits over JM10.2, up to 10% bit reduction, with the same PSNR quality. At the same bit rates, our algorithm has about 0.3-0.4 dB PSNR gain.