Of itu-t sg16 wp3 and iso/iec jtc1/SC29/WG11

6.4.7Signalling of cropped inter-layer references (3)

Contributions in this area were primarily addressed in BoG activity (M0436).

JCTVC-M0436 Report of Non-3V high-level syntax BoG [M. M. Hannuksela (BoG coordinator)]

• 
  The BoG recommended having a discussion in the plenary or track meeting whether other scaling factors than 1.5 and 2 are to be supported in SHVC.
  
• 
  The BoG recommended having a discussion in the plenary or track meeting whether region-of-interest scalability is to be supported in SHVC.
  
• 
  The BoG agreed that the use cases where different layers have different picture aspect ratios is relevant. It was noted that some of the following contributions can be used to respond to this need. Agreed.
  
• 
  M0044 is for further study.
  
• 
  M0219 / M0309 / M0274:
  
  • 
    M0219 crops the reference layer. No action.
    
  • 
    M0309 sends offsets (in VPS) to specify the relative spatial alignment of the base & enhancement layers (without cropping the base layer). Regarding "region of interest scalability" – should the EL rectangle include regions without a corresponding base layer position? The prior SVC can do a (somewhat restricted) form of this. The entire BL region can be a subset of the EL region or the entire EL region can be a subset of the BL picture region. Decision: Adopt with that restricted form of "ROI" flexibility, but in SPS syntax rather than VPS (exact location left to editor discretion).
    
  • 
    M0274 proposes to allow inter-layer referencing of the region of the reference layer outside of the conformance cropping window. (The current draft specifies the reference to be bounded by the cropping rectangle.) Decision: Adopted (option A in M0274). Software will be provided for both HEVC and AVC base layer operation by the proponents.
    
• 
  M0180 was basically a subset of M0274.
  

Should scaling factors other than 1.0, 1.5, 2.0 be supported? We currently have this capability in the syntax, but do not have the upsampling filter coefficients for intermediate positions in the draft or SHM.

It would be feasible, but it is not clear whether we need such a profile at this time.

If we don't have the flexibility in a profile, we don't need the coefficients.

It was remarked that we don't need it in the working draft, as it is not clear that we need such a profile.

We currently do not have phase offsets for luma or chroma in the WD or SHM.

Defer to later consideration when it becomes clear whether we need a profile with such capabilities.