An efficient fast mode decision algorithm for H.264/AVC intra-prediction

The rate distortion optimization (RDO) technique employed in H.264/AVC improve coding performance significantly, but a very high computational load is introduced. In this paper, an intra prediction mode prepruning algorithm based on orientation gradient is proposed to reduce RDO calculation. In the proposed algorithm, the gradients between the reference pixels and the current block pixels are calculated in all the prediction directions, and then the prediction modes with larger gradient are skipped in the prediction process. Experimental results demonstrate the proposed algorithm saves more than half of the encoding time with negligible PSNR loss or bit rate increase.