JVET-AL0155 AHG9: Further fixes and cleanup on GFV and GFVE SEI messages [J. Chen, B. Chen, Y. Ye (Alibaba)]

Aspect 1: remove the inference for the syntax elements gfv_num_matrices_equal_to_num_kps_flag[ i ], gfv_num_matrices_info[ i ], gfv_matrix_width_minus1[ i ], gfv_matrix_height_minus1[ i ] gfv_num_matrices_minus1[ i ] and gfv_matrix_for_3D_space_flag[ i ] in case of prediction being enabled.

Aspect 2: modify the inference for the syntax element gfv_matrix_for_3D_space_flag[ i ] to align the semantics and simplify the inference for the syntax elements gfv_matrix_width_minus1[ i ] and gfv_matrix_height_minus1[ i ].

Aspect 3: modify the inference condition for the syntax elements gfv_matrix_element_precision_factor_minus1 and gfv_num_matrix_types_minus1 for text cleanup.

Aspect 4: remove redundant process in the derivation of variable numMatrices[ i ].

Aspect 5: remove unnecessary constraint on gfv_num_matrix_types_minus1

Aspect 6: remove unnecessary constraint on numMatrices[ i ], matrixWidth[ i ] and matrixHeight[ i ].

Aspect 7: add the inference for the syntax elements gfve_matrix_element_precision_factor_minus1, gfve_num_matrices_minus1, gfve_matrix_height_minus1[ i ] and gfve_matrix_width_minus1[ i ] which is currently missing from the text.

Aspect 8: change a constraint in VVC spec. to allow signalling multiple GFV and GFVE SEI messages with different content within one picture unit.

Aspect 1, Aspect 2, Aspect 4 agreed. (Editorial)

For aspect 3, the change to semantics of gfv_matrix_element_precision_factor_minus1 is agreed, with addition of removing “when gfv_matrix_present_flag is equal to 1”. For the semantics of gfv_num_matrix_types_minus1, can just say when “gfv_matrix_pred_flag is equal to 1". Aspect 3 agreed with noted changes and editorial cleanup delegated to the editors.

Further discussion requested onaspect 5, aspect 6.

Aspect 7, Aspect 8 agreed.

Further discussed on 1 April 2025.

Regarding aspect 5 and 6, the meaning of the word “each” in the constraint that is being removed was unclear.

Aspects 5 and 6 agreed.