JVET-P0599 Non-CE3: Cleanup of interpolation filtering for intra prediction [A. Filippov, V. Rufitskiy (Huawei)]
This document presents a cleanup of interpolation filtering process by replacing 4-tap “Gaussian” filter with a 4-tap smoothing filter obtained by convolving a linear filter with 3-tap FIR filter that has coefficients of [1, 2, 1]/4. Over VTM-6.0, this modification reportedly shows the overall results of 0.00% (Y), -0.02% (U), -0.01% (V) for AI configuration and -0.02% (Y), 0.07% (U), -0.01% (V) for RA configuration. Both encoding and decoding time values are kept appr. 100% for AI and RA configurations.
It is claimed by the proponent that the coefficients of the proposed filter coefficients are very similar to the current filter coefficients (fG in spec), but the observed frequency response issues with the current fG filter in VVC are fixed and some potential visual artefacts are avoided. The proponent also provided screenshots captured from decoded sequences.
It is questioned whether the visual artefact is significant.
It was commented by a non-proponent that the proposed cleanup of the fG interpolation filter is good to have and there is some minor gain.
The BoG recommended adoption of JVET-P0599-v3 (cleanup).