notes2ubit.py

# import os.path
from collections import deque
import read_midi as rmidi

UBIT_MIN_TIME = 1
UBIT_NOTES = "c#d#ef#g#a#b"
UBIT_RESOLUTION_MAG = 8         # resolution magnification
UBIT_INSTRUCTION_PREFIX = 'let sound: string[] = []\n' + \
                          'sound = nerds.stringToNoteArray("'
UBIT_INSTRUCTION_SUFFIX = '")\nnerds.playNoteArray(sound, MelodyOptions.Once)\n'


def note2code(note):
    octave = note // 12 - 1
    index = note % 12
    pitch_name = UBIT_NOTES[index]
    if pitch_name == '#':
        pitch_name = UBIT_NOTES[index - 1] + pitch_name
    return f'{pitch_name}{octave}'


def get_notecode_on_ubit(note, velocity, deltatime):
    if velocity <= 0:
        return f'r:{deltatime}'

    code = note2code(note)
    return f'{code}:{deltatime}'


def to_ubit(notes, ubitfile, comments='', timebase=480, tempo=500000, beatdenom=4):

    # if os.path.exists(file):
    #     return -1, f'Output file already exists. path = {file}'

    q = deque()
    with open(ubitfile, 'a') as ubit:

        # utf8comments = comments.decode('UTF-8', 'ignore')
        # utf8comments = comments.encode(encoding='utf-8', errors='replace')
        # if len(comments) > 0: ubit.write(utf8comments)
        if len(comments) > 0: ubit.write(comments)
        ubit.write(f'music.setTempo({60 * 1000000 * beatdenom / 4 / tempo * UBIT_RESOLUTION_MAG :.0f})\n')
        ubit.write(UBIT_INSTRUCTION_PREFIX)

        separator = ''
        delta_time = 0
        for element in notes:

            # delta time
            if type(element) is int:
                delta_time += element

            # event
            elif type(element) is list:
                # focus only on note-on event and note-off event
                #   element = [ event, ch, note, velocity ]

                # convert note-off to note-on(velocity=0)
                if element[0] == rmidi.MIDI_EVENT_NOTE_OFF:
                    element[0] = rmidi.MIDI_EVENT_NOTE_ON   # event
                    element[3] = 0                          # velocity

                if element[0] == rmidi.MIDI_EVENT_NOTE_ON:
                    if delta_time <= 0:
                        q.append(element)
                        continue

                    note = 0
                    velocity = 0
                    while len(q) > 0:
                        (event, ch, note, velocity) = q.popleft()
                        if velocity > 0: break

                    delta = delta_time * 4 * UBIT_RESOLUTION_MAG // timebase
                    if delta <= 0: delta = UBIT_MIN_TIME
                    code = get_notecode_on_ubit(note, velocity, delta)
                    ubit.write(separator + code)
                    delta_time = 0
                    separator = ','

                    q.clear()
                    q.append(element)

            # unknown
            else:
                pass

        # process last note
        if len(q) > 0:
            # convert midi-notes to ubit-notes
            (event, ch, note, velocity) = q.popleft()
            delta = delta_time * 4 * UBIT_RESOLUTION_MAG // timebase
            if delta <= 0: delta = UBIT_MIN_TIME
            code = get_notecode_on_ubit(note, velocity, delta)
            ubit.write(separator + code)

        ubit.write(UBIT_INSTRUCTION_SUFFIX)

        ubit.write('\n')

    return 0, f'Successfully output code for microbit. {ubitfile}'