JVET-K0100 CE6-Related: Matrix multiplication based NSST with reduced memory map [M. Salehifar, M. Koo, J. Lim, S. Kim (LGE)]
A non-separable secondary transform (NSST) called reduced secondary transform (RST) was proposed and investigated in CE 6.2.6.
A direct matrix multiplication NSST for 4x4 NSST (16x16 direct matrix multiplications) and 8x8 NSST (16x64 direct matrix multiplication) is introduced and investigated in this contribution. relative to a full secondary transform, this reduces the multiplication and multilayer complexity. Also results with memory reduction also reported.
This uses 16 secondary transform kernels instead of ~100 as used in the CE test.
Ordinarily, implementing a secondary transform larger than 4x4 has high complexity. This proposal use a sparse matrix decomposition to simplify the computation. The number of transform kernels is also reduced.