It scales down MP4 files to 720p.

scale_down_all.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""
Task: to reduce the resolution of all videos to 720p in a folder without delving into the subdirectories.
If a video is already in low resolution, the script just copies it.

Usage:
Run it in the video folder and specify as an argument
the folder where you want to save the result.

cd some_folder
python3 path/to/the/script.py output_folder/

License: WTFPL
"""

from argparse import ArgumentParser
from pathlib import Path
import sys
import os
import shutil
import subprocess


def main():
    parser = ArgumentParser(prog='scale_down_all.py',
            description="It scales down all MP4 of the current directory to 720p.")
    parser.add_argument('destination')

    args = parser.parse_args()
    output = Path(args.destination).expanduser()

    if not output.is_dir():
        print("The destination folder does not exists. Please create it and try again.")
        sys.exit(1)

    input_folder = Path.cwd()
    frame_extensions = ["mp4"]

    file_list = [
        file_path
        for file_path in input_folder.iterdir()
        if file_path.is_file()
        and file_path.suffix[1:].lower() in frame_extensions
    ]

    get_h_opts = 'ffprobe -v error -select_streams v:0 -show_entries stream=height -of csv=p=0'

    ffmpeg_main_options = '-vf scale=-2:720 -c:v libx264 -preset fast -tune fastdecode -crf 28 -pix_fmt yuv420p'.split(" ")

    for f in file_list:
        height = int(os.popen(get_h_opts + " \"{}\"".format(f.name)).read())
        if height <= 720:
            shutil.copy(f, output)
            print("{}: COPIED (h={})".format(f.name, height))
        else:
            ffmpeg_options = ["ffmpeg", "-i", str(f.name)] + ffmpeg_main_options + [str(output / f.name)]
            subprocess.check_call(ffmpeg_options)
            print("{}: OK".format(f.name))


if __name__ == "__main__":
    main()