Modification of intra angular prediction in HEVC

Intra prediction of the emerging High Efficiency Video Coding (HEVC) standard has new features that the existing video coding standard H.264/AVC does not have. One example is that new angular prediction modes are added. Finer prediction directions enable to reduce the prediction error energy by making the predicted signals more flexibly. A method to make reference samples for the intra angular prediction plays an important role in terms of the coding efficiency. In the angular prediction of HEVC, a simple 2-tap linear filter is used to make reference samples. In this paper, the reference samples are generated by the conventional 2-tap linear filter or a DCT-based interpolation filter. The proposal improves the intra prediction performance especially for small prediction units such as 4x4 and 8x8. The average coding gains against the anchor of HEVC test model (HM6.0) were about 0.34% and 0.31%, when the tap length of DCT-IF is set to four and six, respectively. The maximum coding gains were about 2.2%, 3.3%, and 3.9% for each component (Y, Cb, and, Cr). In the case of four tap interpolation, the average run-times of encoding and decoding were about 102.84% and 100.96%, respectively.