The metronome may work with or without a slave MIDI file.
In the first case the tempo will be fixed and is helpful only if the audio/video song was recorded using the click and the song starts exactly on a beat. So not very useful most of the time.
The right way however, is by linking a midi file which generates the tempo. The two files must be aligned using any audio/midi sequencing application.
See QMidi Help or:
http://www.mixagesoftware.com/en/qmidi/qmidi_help.htmlMedia > Supported media
http://www.mixagesoftware.com/en/qmidi/tutorials.html#screencast6
Mixage Software
www.mixagesoftware.com
support@mixagesoftware.com