JVET-AQ0092 AHG9: On the FGRC SEI message [Y.-K. Wang, J. Xu (Bytedance)]
This contribution proposes the following changes to the FGRC SEI message:
- In the VVC interface text for FGRC, infer the film grain synthesis picture width and height to be sps_pic_width_max_in_luma_samples and sps_pic_height_max_in_luma_samples, respectively.
- Move the persistence flag to be earlier, similarly as in almost all other SEI messages with cancel and persistence flags.
- Update the condition on when conforming decoders shall ignore FGRC SEI messages with fgr_alpha_channel_adaptation_flag equal to 1, such that the constraint is updated to be as follows:
When a CVS does not contain an SDI SEI message with sdi_aux_id[ i ] equal to 1 and sdi_associated_layer_idx[ i ][ j ] equal to the index of the current layer in the SDI SEI message for at least one pair of values of i and j, decoders conforming to this version of this Specification shall ignore (i.e., remove from the bitstream and discard) the FGRC SEI messages with fgr_alpha_channel_adaptation_flag equal to 1.
- Update the condition on when SDI SEI message sdiA shall be present in the CVS, such that the constraint is updated to be as follows:
It is a requirement of bitstream conformance that, when fgr_alpha_channel_adaptation_flag is equal to 1, an SDI SEI message sdiA that satisfies all the following shall be present in the CVS:
– Let currLayerId and currLayerIdx be, respectively, the layer identifier of the current layer and the index of the current layer in the SDI SEI message such that sdi_layer_id[ currLayerIdx ] is equal to currLayerId.
– There is at least one value of i in the range of 0 to sdi_max_layers_minus1, inclusive, such that sdi_aux_id[ i ] is equal to 1.
– For at least one of such i values, there is at least one value of j in the range of 0 to sdi_num_associated_layers_minus1[ i ], inclusive, such that sdi_associated_layer_idx[ i ][ j ] is equal to currLayerIdx.
– sdiA precedes the FGRC SEI message in decoding order.
- Remove the persistence specification of the alpha channel sample values in the semantics of the FGRC SEI message, as the same persistence specification always exists in the ACI SEI message semantics.
For proposal 1, the language needs to be updated to refer to the max cropped decoded picture size variable rather than the max decoded picture size.
Agreed to item 1 with updated language as described above, item 2, item 4, item 5.
It is noted that the SDI SEI does not have a payload type for HEVC, so constraints that require the presence of the SDI SEI are problematic. It is noted that the object mask SEI message in v4 has a problem in that it refers to syntax from the SDI SEI. Could define an interface variable. For object mask it is suggested to move the constraint to VVC interface text. Y. K. Wang to prepare text for this.
If HEVC support were needed, could define a variable in the interface text for both VVC and HEVC and impose the constraint on the variable in VSEI.
For the SEI messages in TuC, can consider if the constraints is not strictly needed and could be removed, or to move them to interface text.
It was suggested that the decoder language could be removed.
For item 3, agreed to remove the existing constraint.
Constituent rectangles (CR) SEI message (1)
Contributions in this area were discussed during 1725–1800 on Wednesday 8 July 2026 (chaired by J. Boyce).