JVET-L0059 CE6-related: Simplification on MTS kernel derivation [K. Choi, K. P. Choi (Samsung)]
This contribution presents a simplification of MTS by removing a dependency between the number of non-zero coefficients and a kernel selection of MTS. MTS in VTM2.0 uses the number of non-zero coefficients to select kernels adaptively in intra mode. If intra and the number of nonzero coefficients is less than two, DST7 kernel is always used both horizontally and vertically. Otherwise, DST7 and DCT8 are evaluated through RDO process to apply transform. The proposed simplification in this contribution is to remove the dependency between the number of non-zero coefficients and a kernel for MTS. Testing results on the proposed method show no BD rate loss on average for All Intra (AI), Random Access (RA), Low Delay B (LDB), and Low Delay P (LDP) configurations, respectively, compared to VTM-2.0.1, and 0.1% loss for AI and no BD rate loss on average for RA, LDB, and LDP configurations, respectively, compared to BMS-2.0.1.
Unification of conditions intra and inter is desirable.
Other proposal targeting that issue: JVET-L0395, which is however mainly targeting other aspects and unifies ia way that is not simplified.
Decision: Adopt JVET-L0059.