There are additional boxes in T.801 / 15444-2 Annex M that are used in various places.

I'm particularly interested in:

• association box (superbox) - asoc, M11.11
• label box - lbl , M11.13
• reader requirements box - rreq, M11.1

Possibly interested in:

• compositing layer header (superbox) - jplh, M11.7
• opacity box - opct , M11.7.6
• codestream registration box - creg, M11.7.7

The first three are used in GMLJP2 (e.g. georeferenced imagery from satellites), and the last three are used in a derived profile from DGIWG.

More generally, we should possibly have feature gates for tolerant parsing (since readers are meant to ignore unknown boxes), and maybe these extensions. There are definite advantages to fast-fail during development, but at some stage we need to skip...