grandpianist_convert.py

#!/usr/bin/python3
import mido, sys

mid = mido.MidiFile(sys.argv[1])
new_track = mido.MidiTrack()

sustain = 0
last = 0
t = 0
for ev in mido.merge_tracks(mid.tracks):
    t += ev.time
    ev.time = t - last
    if ev.type in ("time_signature", "set_tempo"):
        new_track.append(ev)
        last = t
    elif ev.type in ("note_on", "note_off"):
        new_track.append(ev)
        last = t
    elif ev.type == "control_change":
        if ev.control == 64:
            ev.value = 127 if ev.value > 64 else 0
            if ev.value != sustain:
                new_track.append(ev)
                last = t
                sustain = ev.value

new_mid = mido.MidiFile(type=0)
new_mid.ticks_per_beat = mid.ticks_per_beat
new_mid.tracks.append(new_track)
new_mid.save(sys.argv[2])