I will eventually adapt DCCCONV to do MP1->MPP as well as MPP->MP1 (and I’ll work on other sample frequencies besides 44.1kHz too). But it may take a while before I get to it. If you write it first, your version will be used. As I implied before: I welcome any reasonable pull request and you should have write access to CDex and twolame in the DigitalCompactCassette group on Github. That means you’re free to change things if you want and when you want. You don’t have to ask me if I want to do it first 
I don’t see myself writing my own MP1 encoder/decoder any time soon. that’s already been done by many others and I’d rather work on things that haven’t been done yet.
===Jac
EDIT: Click here for information about the DCCU tool that converts between MPP and MP1 and vice versa.