Metadata OBU for user-defined information?

[bradh]

The note in Section 5.8 of the spec says (in part):

The exact syntax of metadata_obu is not defined in this specification when metadata_type is equal to a
value reserved for future use or a user private value. Decoders should ignore the entire OBU if they do not
understand the metadata_type.

I understand (from Section 6.7.1) that I can use anything in the range 6 to 31 as user-defined private. So I'll choose 6 (or whatever). However, how do I know if the metadata_type is really "my" private data, rather than someone else's data who happened to choose the same number? Is there some process for registration, or another deconfliction process?

Or can I register something in the AOM range (32-) to create some kind of namespace'd (URN, UUID, whatever) metadata, functionally similar to User Defined Unregistered SEI?

[maryla-uc]

I don't know the exact answer to this question, but maybe the METADATA_TYPE_ITUT_T35 metadata type could fit your needs? This one does have a registration mechanism, where you have to get a "Manufacturer Code", also known as "Terminal Provider Code" for your company. The list of national authorities delivering codes manufacturer codes can be obtained from here https://www.itu.int/pub/T-SP-T.35B-2012
For example, for North America, the information is here.
Country codes can be obtained here https://www.itu.int/pub/T-SP-T.35-2012
(I know this question is almost 2 years old but maybe this can be useful to someone).

[bradh]

Thanks @maryla-uc

That isn't quite what I had in mind. In most of the NAL Unit based specs, T-35 is one of the types (often 5) and there is a parallel user defined unregistered type (often 6).

However your METADATA_TYPE_ITUT_T35 reference got me to https://aomediacodec.github.io/av1-hdr10plus/ which I guess is a template for how it could be worked through - as a parallel spec.