join.py

import ffmpeg
import os

def join_artifacts():
    audio_in = ffmpeg.input('audio_out.mp3')
    video_in = ffmpeg.input('video_out.mp4')
    ffmpeg.concat(video_in.filter("subtitles", "audio_out.srt"), audio_in, v=1, a=1).output('av_out.mp4').run()
    av_path = "av_out.mp4"
    return av_path