Early CU size determination in HEVC intra prediction using Average Pixel Cost

The HEVC (H.265) standard has brought in significant improvement in terms of coding efficiency. However, this reduction in bit rate (almost half) comes along with an increase in complexity resulting in a very high compression time. This paper proposes a novel method to reduce the complexity in the intra-mode encoding process. We have defined a new term called the Average Pixel Cost (APC) for a CU. When the APC of a CU is below a specified threshold, the splitting process is stopped and therefore the encoder no longer needs to address the smaller CUs in the quad-tree. This results in considerable time saving for the encoder with negligible deterioration in quality and bitrate. Experimental results, based on this method alone, produced an average reduction of 31.3% in compression time in HM 10.0 with an increase of 0.7% in bitrate along with a negligible decrease of PSNR (-0.03 dB) using an APC threshold of 20.