JVET-M0299 CE11: Deblocking for 4 x N, N x 4 blocks and 8 x N, N x 8 blocks that are not aligned with 8 x 8 sample grid (test 11.2.1) [K. Andersson, Z. Zhang, R. Sjöberg (Ericsson), A. M. Kotra, J. Chen, S. Esenlik, B. Wang, H. Gao (Huawei), C.-M. Tsai, C.-W. Hsu, T.-D. Chuang, C.-Y. Chen, Y.-W. Huang, S.-M. Lei (MediaTek)]

This contribution document reports the results of the core experiment CE11.2.1, which is a joint proposal from Ericsson, Huawei and MediaTek Inc. VTM-3.0 does not apply deblocking filter for some edges belonging to the blocks whose size is Nx4, 4xN blocks and also for some blocks whose size is Nx8, 8xN where N value can be upto 64 samples. This test applies deblocking on 4x4 grid to not only allow deblocking of Nx4, 4xN, Nx8 and 8xN blocks aligned with the current 8x8 sample grid but also for the Nx4, 4xN, Nx8, 8xN blocks that are not aligned on the current 8x8 sample grid. The number of samples to read and modify during deblocking filtering is limited to allow for parallel friendly processing. For a given edge, if at least one of the blocks sharing the edge has a size of 4 samples (orthogonally) then the VTM-3.0 weak deblocking filter is chosen to be applied. Furthermore, the weak filter is constrained to only modify one sample on either side of the edge.

Subjective analysis shows that when compared to the Anchor (VTM-3.0), the proposed test improves the subjective quality of sequences.

Objective results show luma BD-Rate gain with negligible run-time changes.

Over VTM 3.0 Anchor with ALF OFF (AI, RA, LDB, LDP): Luma BD-Rate of -0.05%, -0.23%, -0.21%, -0.36% is achieved with negligible run-time changes.

Over VTM 3.0 Anchor with ALF ON (AI, RA, LDB, LDP): Luma BD-Rate of 0.02%, -0.12%, -0.14%, -0.18% is achieved with negligible run-time changes.