JVET-K0068 CE2 related: Hadamard Transform Domain Filter [V. Stepin, S. Ikonin, R. Chernyak, J. Chen (Huawei)]
This contribution proposes in-loop filter in 1D Hadamard transform domain which is applied on CU level after reconstruction and has multiplication free implementation. Proposed filter is applied for all CU blocks that meet the predefined condition and filter parameters are derived from the coded information. It is reported that for the random access configuration the proposed method provides 0.50% of luma BD-rate saving with 105% encoding time and 104% decoding time compared to VTM 1.0.
Filtering is done in the Hadamard domain, applying a weight to the Hadamard coefficients that depends on the coefficients and the quantization (somewhat similar as a Wiener filter frequency domain equation). The attenuation factor becomes lower for higher QP. Furthermore, a threshold is applied.
The Hadamard transform is only applied within the current transform block, not overlapped (in the same position in the processing chain as the bilateral filter).
A lookup table is required which is approx. 17 k bytes.
Average gain in VTM is 0.5%, BMS 0.4%
Should be compared if it is interdependent with bilateral filter – include in the same sub CE as bilateral filter.