Entity Groups require version and flags, but are not specified

[bradh]

In ISO/IEC 14496-12:2022 Section 8.18.3.2, the syntax for EntityToGroupBox requires a grouping_type, version and flags.

aligned(8) class EntityToGroupBox(grouping_type, version, flags) extends FullBox(grouping_type, version, flags) { ...}

However most of the concrete instances I checked (aebr, afbr, albc, altr, brst, dobr, eqiv, favc, fobr, iaug, oval, ovbg, pano, slid, ster, tsyn, vipo, vvcb, wbbr, ) do not specify the version or flags. The oval and ovbg examples (OMAF) are particularly weird.

There are examples that do (acgl, amgl, opeg, swtk - which is all of the grouping_types from 14496-15, except vvcb).

Also, I didn't check eply or swpc from V3C-SYS.

Suggest adding some default values to either the syntax for EntityToGroupBox (not sure if template is valid there), or adding some explanatory / note text, or both. Perhaps something like "Unless specified otherwise for a particular grouping_type, the version and flags are 0."

[mhannuksela]

Thanks for reporting the issue. In the 2nd DIS of ISOBMFF 8th Edition, subclause 8.18.3.3, the use of version and flags of the EntityToGroupBox has been specified as follows:

version shall be 0 unless defined otherwise for the grouping_type. Any values of flags such that (flags & 0x000FFF) is not equal to 0 are reserved. The values of flags shall be such that (flags & 0xFFF000) is equal to 0 unless defined otherwise for the grouping_type.

[cconcolato]

Closing this issue which seems to be addressed. Reopen if needed.

[podborski]

probably was related to https://github.com/MPEGGroup/FileFormat/issues/44