jams_to_midi_converter.py

import os
import pretty_midi
import jams

def jams_to_midi(filepath, q=1):
    # q = 1: with pitch bend. q = 0: without pitch bend.
    jam = jams.load(filepath)
    midi = pretty_midi.PrettyMIDI()
    annos = jam.search(namespace='note_midi')
    if len(annos) == 0:
        annos = jam.search(namespace='pitch_midi')
    for anno in annos:
        midi_ch = pretty_midi.Instrument(program=25)
        for note in anno:
            pitch = int(round(note.value))
            bend_amount = int(round((note.value - pitch) * 4096))
            st = note.time
            dur = note.duration
            n = pretty_midi.Note(
                velocity=100 + np.random.choice(range(-5, 5)),
                pitch=pitch, start=st,
                end=st + dur
            )
            pb = pretty_midi.PitchBend(pitch=bend_amount * q, time=st)
            midi_ch.notes.append(n)
            midi_ch.pitch_bends.append(pb)
        if len(midi_ch.notes) != 0:
            midi.instruments.append(midi_ch)
    return midi


def convert_jams_to_midi(folder, q=1):
    files = [name for name in os.listdir(folder) if name.endswith(".jams")]
    for filepath in files:
        midi_filepath = filepath.split(".")[0]
        midi_filepath = os.path.join(folder, midi_filepath + ".mid")
        filepath = os.path.join(folder, filepath)
        midi = jams_to_midi(filepath, q)
        midi.write(midi_filepath)