The Joint Collaborative Team on Video Coding (jct-vc) of itu-t wp3/16 and iso/iec jtc 1/ sc 29/ wg 11 held its tenth meeting during 11-20 July 2012 at the City Conference Centre (ccc), a k. a

JCTVC-J0074 AHG10 Hooks for Scalable Coding: Sequence Parameter Set Design [M. M. Hannuksela (Nokia)]

It is asserted that the SVC and MVC extensions of H.264/AVC have at least the following shortcomings when it comes to high-level syntax design.

1. 
   Extending H.264/AVC, SVC, and MVC with new scalability types, such as depth views, has been and is complicated due to different assignments of NAL unit types to VCL and non-VCL NAL units, the HRD being dependent on the assignment of NAL units to VCL and non-VCL NAL units, and the sub-bitstream extraction process(es) ignoring any future scalable extensions.
   
2. 
   A different sequence parameter set is needed even if very few syntax element values (e.g. only profile and level indications) change between layers (in SVC) or views (in MVC).
   

The following kinds of modifications are proposed to reportedly avoid problems similar to those faced with SVC and MVC:

1. 
   It is proposed to reserve a few NAL unit type values specifically for VCL NAL units, e.g. NAL unit types 9 to 12.
   
2. 
   It is proposed to specify a sub-bitstream extraction process for HEVC version 1 with temporal_id and a set of reserved_one_5bits values as inputs.
   
3. 
   Sequence parameter set RBSP may use temporal_id greater than 0 to convey proper profile and level information and HRD parameters for temporal_id-based bitstream subsets.
   
4. 
   Sequence parameter set syntax and semantics are modified to allow copying syntax elements other than profile and level indications from another sequence parameter set of the same seq_parameter_set_id.
   
5. 
   The HRD parameters for conformance are taken from the sequence parameter set of the highest layer (even if were not decoded).
   

Regarding aspect number 5, there was some discussion of how it would be possible to deactivate a layer after a new CVS begins that has the same SPS ID as used in some prior CVS.

It was remarked that operation point definitions in the VPS may be a way to address some of these aspects. Another participant remarked that this may mean that the base layer decoder needs to pay attention to the VPS.

Some participants remarked that aspect number 3 may not be necessary, as there could be other ways to deal with this.

It was remarked that aspect number 4 may not be completely necessary, and seems dependent on aspect number 3.

A participant suggested that it would be desirable to examine which parts of the proposed text are associated with which aspects of the proposal.

Aspect number 2 seemed the most generally supported by the group. Aspect number 1 was also suggested as potentially ready for action.

See notes relating to J0562.