Early detection algorithms for 4×4 and 8×8 all-zero blocks in H.264/AVC

H.264 is the latest HDTV video compression standard, which provides a significant improvement in coding efficiency at the cost of huge computation complexity. Provided that discrete cosine transform coefficient(DCT) blocks can be quantized to all zeros, the process of transform and quantization on this all-zero block(AZB) can be skipped, which will reduce significant redundant computations. In this paper, a theoretical analysis is performed for the sufficient condition for AZB detection. As a result, two partial sum of absolute differences (SAD) based 4×4 AZB detection algorithm are derived. Furthermore, a quantization parameter (QP) oriented 8×8 AZB detection algorithm is proposed according to the AZB's statistical analysis. Experimental results show that the proposed algorithms outperform the previous methods in all cases and achieve major improvement of computation reduction in the range from 12.16% to 42.68% for 4×4 transform, from 4.86% to 73.55% for 8×8 transform. The computation reduction increases as the QP increases.