The JPEG-2000 standard says that the file type box contains a series of compatibility list fields. It says this about each field:
This field is encoded as a four-byte string of ISO/IEC 646 characters.
Here is a compatibility list field from one JPEG-2000 file (hex bytes):
00 00 00 B5
How is that four-byte encoding of a string represented in XML, given that hex 00 (nul) is not a valid character in XML?