Opened 2 years ago

Closed 2 years ago

#1451 closed defect (fixed)

Spec/SW mismatch: chroma interpolation with RPR and 4:4:4

Reported by: fbossen Owned by:
Priority: minor Milestone: VTM-12.0
Component: VTM Version: VTM-11.2
Keywords: Cc: ksuehring, XiangLi, fbossen, jvet@…

Description

In section 8.5.6.3.1 of the spec, the variables refx_C and refy_C are derived and used to determine the phase of the interpolation filter to use:

xFrac_C = refx_C & 31 (911)
yFrac_C = refy_C & 31 (912)

The values of refx_C and refy_C are generally even when processing 4:4:4 content. However, when RPR-related scaling occurs, refx_C and refy_C may be odd, meaning that any of 32 phases of the interpolation filter may be used.

The VTM currently restricts chroma interpolation to use one of the 16 "even" phases of the filter when processing 4:4:4 content. For the 4:4:4 case, the frac parameter to the InterpolationFilter::filterHor function is a 4-bit value which is multiplied by 2 to determine the phase to use.

There is thus a mismatch between text and software when equations (911) and (912) yield odd values for xFrac_C or yFrac_C.

Change history (2)

comment:2 Changed 2 years ago by XiangLi

  • Milestone set to VTM-12.0
  • Resolution set to fixed
  • Status changed from new to closed

Fixed as suggested.

Note: See TracTickets for help on using tickets.