If predict_cr_scaling_flag is equal to 1, the variables cr_mult, cr_luma_mult, and cr_offset are set equal to the variables cr_mult, cr_luma_mult, and cr_offset in the film grain parameter set indicated by film_grain_param_set_idx equal to film_grain_param_set_idx_for_prediction.
However, the syntax table is unclear and suggests these values are present in the bit-stream.
Same comment applies for cb_mult, cr_luma_mult, cr_offst.
Semantics state that:
If predict_cr_scaling_flag is equal to 1, the variables cr_mult, cr_luma_mult, and cr_offset are set equal to the variables cr_mult, cr_luma_mult, and cr_offset in the film grain parameter set indicated by film_grain_param_set_idx equal to film_grain_param_set_idx_for_prediction.
However, the syntax table is unclear and suggests these values are present in the bit-stream.
Same comment applies for cb_mult, cr_luma_mult, cr_offst.