Most IR protocols are fairly simple, with one on/off burst pair denoting a binary zero and a second burst pair representing a binary 1.  XMP uses 16 different burst pairs to represent the hexadecimal digits 0x0 up to 0xF.  Typically learning hardware assumes that the signal has only a few distinct burst pairs, and is confused by XMP. If learning is the only way to enter the IR signal, there probably isn't anything you can do.