4 x 4 SAD and SATD based All Zero Block Detection Algorithm in H.264/AVC

Q. Liu, Y. Huang, and T. Ikenaga (Japan)


All zero block detection, SAD, SATD, H.264


After transform and quantization, if all the coefficients of the block’s residue data are zero, this block is called all zero block (AZB). Provided that an AZB can be detected early, the process of transform and quantization on an AZB can be skipped, which reduces significant redundant com putations. In this paper, a theoretical analysis is performed for the sufficient condition for AZB detection. As a re sult, a partial SAD based 4 × 4 AZB detection algorithm is derived. And then, a hardware-oriented AZB detection algorithm is proposed by modifying the order of SAD cal culation, which is easy to be implemented into PPSAD and SAD tree Integral Motion Estimation(IME) hardware ar chitecture. Furthermore, based on residual data’s Gaussian distribution, a SATD based all zero block threshold is pro posed. Experimental results show that the proposed algo rithm outperforms the previous methods in all cases and achieves major improvement of computation reduction in the range from 6.7% to 42.3% for SAD based AZB detec tion. The computation reduction increases as QP increases. For SATD based proposed AZB detection algorithm, the AZB detection rate increased from 6% to 62.61%.

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