Kdenlive beat sync

beatfinder.py

import argparse

import librosa  # you need librosa to get this working
import datetime


def parse_delta(s):
    date = datetime.datetime.strptime(s, "%H:%M:%S")
    return datetime.timedelta(hours=date.hour, minutes=date.minute, seconds=date.second)


def main():
    parser = argparse.ArgumentParser(
        prog='Kdenlive beatfinder',
        description='Creates timeline guides matching the song beat')

    parser.add_argument('input_file')
    parser.add_argument('--output_file', required=False, default="beats.txt")
    parser.add_argument("--bpm", type=float, default=None)
    parser.add_argument("--offset", default="0:00:0")
    parser.add_argument("--tightness", type=float, default=100)
    args = parser.parse_args()
    offset = parse_delta(args.offset)
    y, sr = librosa.load(args.input_file)

    tempo, beat_frames = librosa.beat.beat_track(y=y, sr=sr, bpm=args.bpm, tightness=args.tightness)
    beat_times = librosa.frames_to_time(beat_frames, sr=sr)
    print(f"{args.input_file} BPM: {tempo:.2f}")
    print(f"Writing timeline guides to {args.output_file}...")
    with open(args.output_file, "wt") as f:
        for i, seconds in enumerate(beat_times):
            f.write(f"{str(datetime.timedelta(seconds=seconds) + offset)} {i}\n")


if __name__ == '__main__':
    main()

Example usage:

python beatfinder.py waster.mp3 # find beats and write to beats.txt
python beatfinder.py waster.mp3 --offset 00:00:15 # set 15 seconds offset
python beatfinder.py waster.mp3 --bpm 120 --output_file /tmp/beats.txt # set track bpm (optional)