Reencode a music library from FLAC to Opus

encode_music.py

import pathlib
import subprocess
import sys


REENCODE_EXTENSIONS = {'.flac', '.m4a', '.alac'}
COPY_EXTENSIONS = {'.jpg', '.jpeg', '.png', '.mp3', '.opus', '.ogg'}
IGNORE_EXTENSIONS = {'.log', '.cue', '.txt'}


def _iter_tree(root: pathlib.Path):
    if not root.is_dir():
        raise ValueError(f'{root} is not a directory')

    for child in sorted(root.iterdir()):
        if not child.is_dir():
            yield child
        elif child.is_dir():
            for descendent in _iter_tree(child):
                yield descendent


def encode_music_tree(src: pathlib.Path, dest: pathlib.Path):
    for src_file in _iter_tree(src):
        rel = src_file.relative_to(src)
        dest_file = dest / rel

        file_name = src_file.name
        if file_name.startswith('.') or any(file_name.lower().endswith(ext) for ext in IGNORE_EXTENSIONS):
            continue
        elif any(file_name.lower().endswith(ext) for ext in COPY_EXTENSIONS):
            command = ['cp', src_file, dest_file]
        elif any(file_name.lower().endswith(ext) for ext in REENCODE_EXTENSIONS):
            dest_file = dest_file.parent / (file_name.rsplit('.', 1)[0] + '.opus')
            command = ['ffmpeg', '-i', src_file, '-vn', '-c:a', 'libopus', '-b:a', '128000', dest_file]
        else:
            ext = file_name.rsplit('.', 1)[-1]
            if ext != file_name:  # don't print this for files with no extension
                print(f'unrecognized extension: .{ext}', file=sys.stderr)
            continue

        dest_file.parent.mkdir(parents=True, exist_ok=True)
        result = subprocess.run(command, capture_output=True, encoding='utf-8')
        if result.returncode != 0:
            print(result.stderr, file=sys.stderr)
            raise Exception(f"Error running '{' '.join(map(str, command))}'")


if __name__ == '__main__':
    src = pathlib.Path(sys.argv[1]).resolve()
    dest = pathlib.Path(sys.argv[2]).resolve()

    encode_music_tree(src, dest)