In JVET-00636 (Kiran Misra, et al., “Cross-Component Adaptive Loop Filter for chroma”, Joint Video Experts Team (JVET) of ITU-T SG 16 WP 3 and ISO/IEC JTC 1/SC 29/WG 11, 15th Meeting: Gothenburg, SE, 3-12 Jul. 2019, Document: JVET-00636), Cross-Component Adaptive Loop Filter (CC-ALF) is proposed. CC-ALF makes use of luma sample values to refine each chroma component. FIG. 2A illustrates the structure of CC-ALF with respect to the other loop filters according to JVET-00636. In FIG. 2A, the ALF processing is performed after respective SAO (210, 212 and 214). In a conventional video coding system, only ALF Luma 220 and ALF Chroma 230 are used. In JVET-00636, two additional ALF filters, i.e., CC ALF Cb 222 and CC ALF Cr 224 are used to derive adjustment signals to add to ALF processed Cb and Cr using adders 240 and 242 respectively.

In CC-ALF operates by applying a linear, diamond shaped filter to the luma channel for each chroma component as shown in FIG. 2B according to JVET-00636. The filter coefficients are transmitted in the APS, scaled by a factor of 2¹⁰, and rounded for fixed point representation. The application of the filters is controlled on a variable block size and signalled by a context-coded flag received for each block of samples. The block size along with a CC-ALF enabling flag is received at the slice-level for each chroma component. Syntax and semantics for CC-ALF are also disclosed in JVET-00636.