A fast ranking-based method for intra mode decision in H.264/AVC encoder

In this work, a fast ranking-based method for intra mode decision is proposed to reduce the computation load of intra prediction in H.264/AVC encoder. By detecting the block direction, a subset of ranking-based candidates is generated for each block to accelerate the process of mode decision. In the intra 4×4 prediction, the candidate number can be chosen from 2 to 4, instead of 9 modes, to decide the best mode. For the 16×16 prediction mode, instead of 4 modes, only 1 candidate is chosen. Experimental results show that the proposed ranking-based method can provide the scalable R-D curve performance through selecting different numbers of candidate. This method slightly increases the bit-rate (i.e. 3.424% in averaged) with negligible PSNR degradation, compared to the full search method in the reference code.