Wrong inference rule for pred_mode_ibc_flag

[fbarbier]

In specification in 7.4.9.5 Coding unit semantics

When pred_mode_ibc_flag is not present, it is inferred as follows:
- If cbWidth is equal to 4 and cbHeight is equal to 4, pred_mode_flag is inferred to be equal to 1.
- Otherwise ...
[...]
- Otherwise, pred_mode_ibc_flag is infered to be equal to the value of sps_ibc_enabled_flag when decoding an I slice, and 0 when decoding a P or B slice, respectively.

In current VTM implementation, i cannot see where the last inference rule is implemented (accordingly to sps_ibc_enabled_flag and slice_type == I_Slice)

Am i missing something or is it a bug in VTM ?

[fbarbier]

Thanks to Xiaozhong, we arrived to the conclusion that an inference rule shall be modified
from :

–        Otherwise, if both cbWidth and cbHeight are equal to 128, pred_mode_ibc_flag is inferred to be equal to 0.

to:

–        Otherwise, if either cbWidth or cbHeight is equal to 128, pred_mode_ibc_flag is inferred to be equal to 0.

[axink]

Ticket #480 has been marked as a duplicate of this ticket.

[bbross]

Good catch! Thanks!
Fixed in a document we are preparing to be submitted as an editorial input
to the 16th JVET meeting.