Opened 5 years ago

Closed 5 years ago

#473 closed defect (fixed)

Wrong inference rule for pred_mode_ibc_flag

Reported by: fbarbier Owned by:
Priority: minor Milestone:
Component: spec Version: VVC D6 vE
Keywords: Cc: ksuehring, XiangLi, fbossen, jvet@…

Description

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 ?

Change history (4)

comment:1 Changed 5 years ago by fbarbier

  • Component changed from VTM to spec
  • Summary changed from Missing inference rule for pred_mode_ibc_flag to Wrong inference rule for pred_mode_ibc_flag

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.

comment:2 Changed 5 years ago by fbarbier

  • Version changed from VTM-6.0rc1 to VVC D6 vE

comment:3 Changed 5 years ago by axink

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

comment:4 Changed 5 years ago by bbross

  • Resolution set to fixed
  • Status changed from new to closed

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

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