Enhanced line-based intra prediction with fixed interpolation filtering

In this paper, a novel intra prediction algorithm, named enhanced line-based intra prediction (ELIP), is proposed to improve the traditional intra prediction methods for image/intra-frame coding. Different from the existing schemes where the interpolation filtering only depends on the intra prediction mode, in the proposed ELIP, the linear filtering coefficients are further refined by imposing both mode and position dependencies. For each intra prediction mode and each position within one block, a set of linear filtering coefficients are obtained from off-line training using the least square method. The proposed algorithm has been implemented in the latest ITU-T VCEG KTA software. Experimental results demonstrate that, compared with the intra coding scheme of KTA with new intra coding tool enabled, up to 0.44dB additional coding gain is achieved by the proposed method, while keeping applicable computational complexity for practical video codecs.