import json

with open("x.json", "r", encoding="utf-8") as f:
    data = json.load(f)

with open("chapters.txt", "w", encoding="utf-8") as f:
    f.write(";FFMETADATA1\n")
    for ch in data.get("chapters", []):
        start = int(ch["start_time"] * 1000)
        end = int(ch["end_time"] * 1000)
        title = ch["title"]

        f.write("[CHAPTER]\n")
        f.write("TIMEBASE=1/1000\n")
        f.write(f"START={start}\n")
        f.write(f"END={end}\n")
        f.write(f"title={title}\n")