Using H.264 coded block patterns for fast inter-mode selection

The support of variable block-sizes, though significantly improves the compression efficiency, imposes a big computational challenge on an H.264 encoder. In this paper, we present a new fast inter-mode decision algorithm based on the coded block pattern (CBP). Specifying which blocks within a macroblock are uncoded, CBP is a good indicator of block-matching accuracy and can be used to reduce the rate-distortion calculation required for mode selection. Experimental results show that the proposed method achieves more than 50% reduction in computation time relative to the exhaustive mode search with negligible degradation in visual quality. Other merits of the proposed method include (1) no extra computation is needed for obtaining CBP; (2) no ad-hoc threshold is involved in the algorithm; (3) in contrast to the previous early-skip algorithm that yields very limited improvement for high-activity videos, the proposed method is highly reliable for various video characteristics.