Mode dependent down-sampling and interpolation scheme for high efficiency video coding

•We establish a prediction distance model to evaluate the intra prediction accuracy.•We analyze the prediction accuracy for down-sampling based coding method.•An adaptive down-sampling and interpolation scheme is proposed.•The intra prediction mode is utilized to design the proposed method.•The proposed scheme achieves coding gains with negligible complexity increase.

In this paper, a mode dependent down-sampling and interpolation scheme is proposed to improve the coding efficiency of the intra prediction module. In the proposed method, we elaborately design the down-sampling structures and interpolation schemes for each directional intra prediction mode by minimizing the spatial prediction distance. The sampled pixels are predicted with a traditional directional intra prediction scheme, and the non-sampled pixels are predicted from the interpolation of their neighboring reconstructed sampling pixels. Both the residuals of the sampled and non-sampled pixels are encoded at last. Experimental results show that the proposed method achieves an average 7.52% bitrate reduction relative to KTA reference software. Since the down-sampling structure and interpolation method is only related to the intra mode, there is no additional overhead at the encoder.