Merge two subtitles (SRT) into a combined SRT file with prefixes.

merge_subtitles.py

import os
import re
import sys
import argparse

def convert_to_vtt(input_srt, output_vtt):
    os.system(f"ffmpeg -i {input_srt} -c:s webvtt {output_vtt}")

def convert_to_srt(input_vtt, output_srt):
    os.system(f"ffmpeg -i {input_vtt} -c:s subrip {output_srt}")

def add_prefix(input_vtt, prefix):
    with open(input_vtt, "r", encoding="utf-8") as file:
        content = file.read()

    content = re.sub(r"(\d+\n)", rf"\1{prefix}: ", content)

    with open(input_vtt, "w", encoding="utf-8") as file:
        file.write(content)

def merge_vtt_files(input_vtt_a, input_vtt_b, output_vtt):
    with open(input_vtt_a, "r", encoding="utf-8") as file_a, open(input_vtt_b, "r", encoding="utf-8") as file_b:
        content_a = file_a.read()
        content_b = file_b.read().replace("WEBVTT\n", "")
        
    with open(output_vtt, "w", encoding="utf-8") as output_file:
        output_file.write(content_a)
        output_file.write("\n")
        output_file.write(content_b)

def main(args):
    convert_to_vtt(args.input_srt_a, args.temp_vtt_a)
    convert_to_vtt(args.input_srt_b, args.temp_vtt_b)

    add_prefix(args.temp_vtt_a, args.prefix_a)
    add_prefix(args.temp_vtt_b, args.prefix_b)

    merge_vtt_files(args.temp_vtt_a, args.temp_vtt_b, args.temp_combined_vtt)

    convert_to_srt(args.temp_combined_vtt, args.output_srt)

    # Clean up temporary files
    os.remove(args.temp_vtt_a)
    os.remove(args.temp_vtt_b)
    os.remove(args.temp_combined_vtt)

if __name__ == "__main__":
    parser = argparse.ArgumentParser(description="Merge two subtitle files with custom prefixes.")
    parser.add_argument("input_srt_a", help="Input SRT file A")
    parser.add_argument("input_srt_b", help="Input SRT file B")
    parser.add_argument("--prefix_a", default="A", help="Prefix for subtitle entries in file A (default: A)")
    parser.add_argument("--prefix_b", default="B", help="Prefix for subtitle entries in file B (default: B)")
    parser.add_argument("--output_srt", default="combined.srt", help="Output combined SRT file (default: combined.srt)")
    
    parser.add_argument("--temp_vtt_a", default="temp-A.vtt", help=argparse.SUPPRESS)
    parser.add_argument("--temp_vtt_b", default="temp-B.vtt", help=argparse.SUPPRESS)
    parser.add_argument("--temp_combined_vtt", default="temp-combined.vtt", help=argparse.SUPPRESS)

    args = parser.parse_args()
    main(args)