Mode decision with enhanced inter-prediction in HEVC

The HEVC standard makes use of inter-prediction to exploit temporal redundancy in order to obtain efficient compression. A novel approach is proposed in this paper where the inter-prediction for a coding unit (CU) is further enhanced by means of simple parametric transformations. The Enhanced Inter-Prediction (EIP) module is embedded within the mode-decision module at a CU level, to obtain a more accurate inter-prediction and hence possibly reducing the residuals before transform and quantisation. The EIP parameters are encoded in the CU header, and the exact rate-distortion (RD) cost after reconstruction is computed to make sure that the EIP is only used when it is effective. The approach is also improved by means of efficient quantisation of the EIP parameters. The optimal quantisation steps for each CU are found following from analytical considerations as illustrated in the paper. Results show consistent improvements over conventional HEVC encoding in terms of PSNR and bitrate performance.