High Efficiency Video Coding (HEVC/H.265), the latest standard in video compression, aims to halve the bitrate while maintaining the same quality or to achieve the same bitrate with an improved quality compared to its predecessor, AVC/H.264. However, the increase in prediction modes in HEVC significantly impacts on the encoder complexity. Intra prediction methods indeed iterate among 35 modes for each Prediction Unit (PU) to select the most optimal one. This mode decision procedure which consumes around 78% of the time spent in intra prediction consists of the Rough Mode Decision (RMD), the simplified Rate Distortion Optimisation (RDO) and the full RDO processes. In this chapter considerable time reduction is achieved by using techniques that use fewer modes in both the RMD and the simplified RDO processes. Experimental results show that the average time savings of the proposed method indeed yields a 42.1% time savings on average with an acceptable drop of 0.075 dB in PSNR and a negligible increase of 0.27% in bitrate.
Saurty, K., Catherine, P. C., & Soyjaudah, K. M. S. (2016). Fast intra mode decision for HEVC. Studies in Computational Intelligence, 650, 361–383. https://doi.org/10.1007/978-3-319-33386-1_18