Merge midi channels

merge_midi.py

"""Merge midi data"""

import argparse
import csv
import glob
import os
import subprocess
import sys

POS_TRACK = 0
POS_TIME = 1
POS_TYPE = 2
POS_CHANNEL = 3
POS_NOTE = 4
POS_VELOCITY = 5
POS_PROGRAM = 4


def collect_filenames(path):
    """Collect filenames from a path that may be a directory"""

    if os.path.isdir(path):
        files = glob.glob(f"{path}/*.mid")
        return files

    return [path]


def merge_midi(path, mode="single_channel"):
    """Merge midi channel/track data"""
    all_files = collect_filenames(path)

    for filename in all_files:
        print(filename, end="")

        csv_filename = f"{filename}.csv"
        cmd = ["midicsv", filename, csv_filename]
        subprocess.run(cmd, check=False)

        data = read_csv(csv_filename)
        for event in data:
            if event[POS_TYPE] in ["Note_on_c", "Note_off_c"]:
                event[POS_CHANNEL] = 0
            elif event[POS_TYPE] in ["Program_c"]:
                event[POS_CHANNEL] = 0
                event[POS_PROGRAM] = 1  # Force to piano

        write_csv(data, csv_filename)

        out_filename = filename.replace(".mid", "_single_channel.mid")
        cmd = ["csvmidi", csv_filename, out_filename]
        subprocess.run(cmd, check=False)
        print(" > Wrote to file", out_filename)

        os.unlink(csv_filename)


def read_csv(filename):
    """Read midi csv file"""

    events = []
    with open(filename, encoding="ISO-8859-1", newline="") as csvfile:
        reader = csv.reader(csvfile, quotechar='"', skipinitialspace=True)
        for row in reader:
            events.append(row)

    return events


def write_csv(data, filename):
    """Write midi csv file"""

    with open(filename, "w", encoding="ISO-8859-1", newline="\n") as csvfile:
        writer = csv.writer(csvfile)
        for row in data:
            writer.writerow(row)
    return filename


if __name__ == "__main__":
    if len(sys.argv) == 1:
        print("Usage: merge_midi [--mode=<mode>] <path>")
        sys.exit(1)

    parser = argparse.ArgumentParser()
    parser.add_argument(
        "-m",
        "--mode",
        default="single_channel",
        help="Set mode for merge strategy",
    )
    parser.add_argument("path", help="Midi filename or path")

    # Returns tuple of known args and unknown args
    (args, _) = parser.parse_known_args(sys.argv[1:])

    print("Mode:", args.mode)

    merge_midi(args.path, mode=args.mode)