ffmpeg-srt-scene

#!/usr/bin/env python3

# ffmpeg-srt-scene: Given a scene index, render that scene with the subtitles baked in.

import argparse
import math
import pathlib
import subprocess

import srt


def timestamp(delta):
    (hours, rem) = divmod(delta.total_seconds(), 3600)
    (minutes, seconds) = divmod(rem, 60)
    (millis, seconds) = math.modf(seconds)

    return f"{int(hours):02d}:{int(minutes):02d}:{int(seconds):02d}.{int(millis * 1000):03d}"


def main():
    parser = argparse.ArgumentParser(
        description="Render a scene with baked-in subtitles, using its SRT index"
    )
    parser.add_argument("input", type=pathlib.Path, help="The input video")
    parser.add_argument(
        "srt", type=pathlib.Path, help="The SRT file to index from",
    )
    parser.add_argument("index", type=int, help="The scene index")
    parser.add_argument("output", type=pathlib.Path, help="The output")
    options = parser.parse_args()

    sub = list(srt.parse(options.srt.read_text()))[options.index - 1]

    start_ts = timestamp(sub.start)
    end_ts = timestamp(sub.end)

    subprocess.run(
        [
            "ffmpeg",
            "-i",
            options.input,
            "-vf",
            f"subtitles={options.srt}",
            "-copyts",
            "-ss",
            start_ts,
            "-to",
            end_ts,
            options.output,
        ]
    )


if __name__ == "__main__":
    main()