Download YouTube videos with optional arguments for trimming

segytb.sh

#!/bin/bash

dirpath="/path/to/directory"
cd "$dirpath"

url=$1
startTimestamps=$2
endTimestamps=$3

scriptname="segytb"

youtube-dl --external-downloader aria2c --external-downloader-args "--file-allocation=none -j16 -x16 -s16 -k10M" --merge-output-format mp4 --format bestvideo+bestaudio -o 'temp.mp4' $url

title=$(youtube-dl --get-filename -o '%(title)s' $url | sed "s/ /_/g")
title="${title}.mp4"

# If user input has more than on argument (other than URL), then execuate the FFmpeg trimming
if [ $# -eq 2 ] || [ $# -eq 3 ]  || [ $# -eq 4 ] 
then
    ffmpeg -i temp.mp4 -ss $startTimestamps -to $endTimestamps -c copy $title
    if [[ -f $dirpath/$title ]]; then
    echo "FFmpeg trimming success!"
    rm temp.mp4
	fi
else
	mv temp.mp4 $title
    echo "${title} Downloaded!"
fi

1. Install aria2c and ffmpeg
2. Define the dirpath to a desired one
3. Execute the below command up to your need

./segytb.sh https://www.youtube.com/watch?v=a3ICNMQW7Ok 

./segytb.sh https://www.youtube.com/watch?v=a3ICNMQW7Ok 00:00:05 00:00:10

4. Done!

You could of course remove argument of using external downloader: aria2c for multi-thread downloading.

aria2c --external-downloader-args "--file-allocation=none -j16 -x16 -s16 -k10M"

N.B. The script fetches the highest quality of video (even if it's .webm format in 4K) and saves it as a mp4 file.