JVET-AP0148 AHG9: On Auxiliary sampling alignment information SEI [S. Wang, Y. Gao, P. Wu, S. Xie, Y. Bai (ZTE)]

It is proposed to add a new flag, asai_affine_scale_xy_equal_flag, in the auxiliary sampling alignment information (ASAI) SEI message. The flag indicates whether the horizontal scaling factor sX and vertical scaling factors sY of the affine transform are equal (including both absolute values and sign bits). When the flag is equal to 1, only the horizontal scaling parameters (asai_affine_scale_x_abs and asai_affine_scale_x_sign_flag) are signalled, omitting redundant vertical scaling parameters. When the flag is equal to 0, both the horizontal and vertical scaling parameters are signalled.

It was suggested that for the simple alignment case it is likely that horizontal and vertical scaling factors would be identical, while in the affine case, it is not particularly likely that they would match.

Further study to consider adding a similar flag to the simple alignment case.

Localization and mapping (LAM) SEI message (5)

Contributions in this area were discussed during 1400–1505 on Wednesday 30 April 2026 (chaired by J. Boyce).