JVET-P0149 AHG18: Disabling LMCS for lossless coding [Z.-Y. Lin, T.-D. Chuang, C.-Y. Chen, C.-W. Hsu, Y.-W. Huang, S.-M. Lei (MediaTek)]

This contribution proposes two methods to achieve lossless coding when luma mapping with chroma residual scaling (LMCS) is enabled at sequence level and transquant bypass mode is enabled at picture level. In Method 1, if the transquant bypass mode is enabled at picture level, it is proposed to force disabling LMCS at slice level. In Method 2, it is proposed to force disabling LMCS for lossless coded blocks and to allow LMCS for lossy coded blocks. Both methods can support lossless coding for an entire picture and lossless coding for a partial picture.

This would only be relevant when lossless functionality was enabled via transquant bypass.

No need to study this in a CE was evident.