MarsSeed [1] filed a deletion request for mp4tools [2]: Project abandoned in 2010. I suggest it's safe to delete this package. Nothing relies on it. FFMPEG and GStreamer can do all the things this tool was capable of, and much more.
[1] https://aur.archlinux.org/account/MarsSeed/ [2] https://aur.archlinux.org/pkgbase/mp4tools/
