Intra prediction with spatial gradients and multiple reference lines

This paper proposes an improved intra prediction method for H.264/AVC. The conventional method uses only adjoining pixels as reference pixels. The residual energy is increased if the decoded pixels are occluded, which would result in low coding efficiency. In addition, the conventional prediction method copies the same weighted prediction value to several of the pixels lying in the prediction direction. However, if the original image exhibits gradations, the residual energy might be increased which would also result in low coding efficiency. To handle these problems, we proposed, separately, two improved methods. One allows the use of distant pixels as well as adjoining pixels. The other generates prediction signals with a spatial gradient. This paper confirms the performance of the combination of the two methods. Simulation results show that the combined method outperforms the proposed methods, in isolation, at high bit-rates.