(CENC) Item auxiliary information box valid values

[bradh]

I am having some trouble understanding the concept for item encryption auxiliary info.

In ISO/IEC 23001-7:2023 Section 8.4.3, the aux_info_type and aux_info_type_parameter semantics just point back to ISO/IEC 14496-12.

However there is some discussion in 8.4.1 that suggests that aux_info_type is intended to be a meaningful value, not just a random integer or 0. For a protected item, it probably should be a known scheme_type value from https://mp4ra.org/registered-types/schemes - or something defined for one of those schemes. Is the intent that aux_info_type is a 4CC?

Or is it just private to and dependent on the scheme_type in the schm box? If so, where is that defined for say cenc? The example I'm looking at has aux_info_type of 0x00 0x00 0x00, 0x00, and aux_info_type_parameter of 0x00, 0x00, 0x00, 0x01,
and I'm lost as to how to interpret that (essential) item property for the auxi item.

Any suggestions?