WARNING: I have not gotten this to produce an .amv which I could successfully play yet on my US212C MP3/AMV player by Actions-Semi (Chinese/native version, you might have better luck translating with your browser). If you get it to work, PLEASE OPEN AN ISSUE OR PR EXPLAINING HOW YOU DID SO. Thanks
I have released a prebuilt binary of this. I couldn't get it to build correctly without passing --disable-mmx to ./configure, so I don't know if that does anything...
Again, let me know if you have better luck than I did!
Original Windows-only "MP3 Player Utilities" available at https://files.mikeylab.com/amvtools.zip [these files came on my player when it arrived]