FridgeSensor/import_midi.py

import struct

# Constants for MIDI to Frequency conversion
A4_MIDI = 69
A4_FREQ = 440.0

def midi_to_freq(note):
    return A4_FREQ * (2 ** ((note - A4_MIDI) / 12.0))

def read_variable_length(data, index):
    value = 0
    while True:
        byte = data[index]
        index += 1
        value = (value << 7) | (byte & 0x7F)
        if not (byte & 0x80):
            break
    return value, index

def parse_midi(filename):
    with open(filename, 'rb') as f:
        data = f.read()
    
    # Check MIDI header
    if data[:4] != b'MThd':
        raise ValueError("Invalid MIDI file")
    
    # Read header values
    header_size = struct.unpack('>I', data[4:8])[0]
    format_type, num_tracks, division = struct.unpack('>HHH', data[8:14])
    index = 14 + (header_size - 6)

    print("Header size:", header_size)
    print("Format type:", format_type)
    print("Number of tracks:", num_tracks)
    print("Division:", division)

    
    notes = []
    active_notes = {}
    last_time = 0
    
    while index < len(data):
        if data[index:index+4] == b'MTrk':
            index += 4
            track_length = struct.unpack('>I', data[index:index+4])[0]
            index += 4
            track_end = index + track_length
            
            while index < track_end:
                delta_time, index = read_variable_length(data, index)
                last_time += delta_time
                event = data[index]
                index += 1
                
                if event == 0xFF:  # Meta event
                    meta_type = data[index]
                    index += 1
                    length, index = read_variable_length(data, index)
                    index += length  # Skip meta event data
                elif event >= 0x80:  # MIDI event
                    status = event & 0xF0
                    channel = event & 0x0F
                    
                    if status in (0x90, 0x80):  # Note On/Off
                        note = data[index]
                        velocity = data[index + 1]
                        index += 2
                        
                        if status == 0x90 and velocity > 0:  # Note On
                            active_notes[note] = last_time
                        elif status == 0x80 or (status == 0x90 and velocity == 0):  # Note Off
                            if note in active_notes:
                                start_time = active_notes.pop(note)
                                duration = last_time - start_time
                                pause_duration = 0 if not notes else start_time - (notes[-1][1] + notes[-1][2])
                                notes.append((midi_to_freq(note), int(duration), int(pause_duration)))
                    else:
                        index += 1  # Skip unknown event
    
    return notes

def generate_c_array(notes):
    c_code = "const struct Note notes[] = {\n"
    for freq, duration, pause in notes:
        c_code += f"    {{{freq:.2f}, {duration}, {pause}}},\n"
    c_code += "};\n"
    return c_code

# Example usage
midi_file = "track_1.mid"  # Replace with your MIDI file
notes = parse_midi(midi_file)
c_array = generate_c_array(notes)
print(c_array)