JVET-L0291 CE3 Related: Extended reference sample construction for longer interpolation filter in intra prediction [S. Yoo, J. Heo, J. Choi, L. Li, J. Choi, J. Lim (LGE)]
In HEVC (and JEM), only a bi-linear interpolation filter was used for prediction of sub-pel position. However, in CE3-Intra prediction and mode coding, longer interpolation filters (i.e., 4-tap and 6-tap filters) are being considered. In the conventional way of reference sample construction, it is not available for the very-end predicted samples (some right bottom samples in a currently predicted block) to refer to the reconstructed samples in the neighbour blocks. In this contribution, an extension of a reference sample construction is proposed for longer interpolation filter. Specifically, the number of the reference samples is extended from the neighbour blocks. The experimental results are reportedly shown that 0.04% and 0.01% BD-rate coding gains from VTM-AI and VTM-RA respectively.
In RA configuration, loss (+0.17/+0.22%) is observed in chroma compared to 4-tap standalone.
No obvious benefit was seen compared to 4-tap.