JVET-AE0123 AHG10: Lagrange multiplier optimization for chroma ALF and CCALF [S.-W. Xie, Y. Gao, M.-H. Jia, Y.-L. Hu, C. Huang, P. Wu (ZTE)]

This contribution reports further results for the RDO method in ALF, which was proposed in JVET-AD0136. Regarding the proposed method, the chroma Lagrange multiplier will be adjusted by a scaling factor when the luma ALF APS transmission flag is ON and the number of history chroma ALF APS is insufficient. With VTM20.0 as anchor and test platform, the reported overall PSNR-Y,U,V BD-rate and {EncT, DecT} variations of this proposal are as follows:

• LDB: 0.05%, -0.80%, -1.18% {100%, 100%}
• LDP: 0.02%, -0.89%, -1.03% {100%, 101%}

As a general policy, encoder optimizations of this kind should equally be applied to the VTM and ECM. In the last meeting, it had specifically been requested to improve the performance of the ECM (where apparently losses had been observed, according to the JVET-AD1000 meeting notes. It was verbally reported that the ECM performance would be similar with the new proposal, but no results were provided.

For VTM, the results look beneficial, chroma gains outweigh the small luma losses.

It was pointed out that for ECM it might be necessary to adjust the multiplier differently.

Further study was encouraged on implementing the method on top of the ECM.

JVET-AE0262 Crosscheck of JVET-AE0123 (AHG10: Lagrange multiplier optimization for chroma ALF and CCALF) [H. Zhang (Tencent)] [late]

AHG13: Film grain synthesis (2)

Contributions in this area were discussed in the BoG reported in JVET-AE0294, and at 1445 on Saturday 15 July 2023 (chaired by JRO).

JVET-AF0122 AhG10: Lagrange multiplier optimization for chroma ALF and CCALF [S.-W. Xie, Y. Gao, M.-H. Jia, Y.-X. Bai, C. Huang, P. Wu (ZTE)]

This contribution reports further results for the RDO Optimization method in ALF, which was proposed in JVET-AD0136 and JVET-AE0123. Regarding the proposed method, the chroma Lagrange multiplier will be adjusted by a scaling factor when the luma ALF APS transmission flag is ON and the number of history chroma ALF APS is insufficient. With VTM-22.0 and ECM-10.0 as anchors and test platforms, the reported overall PSNR-Y, U, V BD-rate and {EncT, DecT} variations of this proposal are as follows:

On top of VTM-22.0:

• LDB: 0.05%, -0.80%, -1.18% {100%, 100%}
• LDP: 0.02%, -0.89%, -1.03% {100%, 101%}

On top of ECM-10.0:

• LDB: 0.04%, -1.89%, -1.60% {100.0%, 100.7%}
• LDP: 0.11%, -1.60%, -1.45% {100.2%, 100.3%}

During the discussion of JVET-AE0123, it was suggested that the multiplier might need to be adjusted for ECM compared to VTM. The proponent reported that experimentations had been conducted to adjust the multiplier, and results show that using the same value for VTM and ECM achieves the most balanced performance among luma and chroma components.

Cross checker reported that VTM results have been completed, but ECM results are still partial at the time of presesntation. VTM results and partial ECM results are matched with that provided by the proponent.

It was asked why this has no effect on RA config. This could be because for RA config parallel encoding is performed.

Whereas the performance for VTM is considered to be overall beneficial...