My media helper script

MediaHelper.bash

#!/usr/bin/env bash
# -*- coding: utf-8 -*-
# Defaults. Change using cli args
SRCDIR="Music/Rick Astley"
OUTDIR="Music/Rick Astley Converted"
# Sometimes change to "opus" if you use yt-dlp or youtube-dl
SRCEXT=mp3
OUTEXT=mp3
# Location of ffmpeg
ffm=/usr/bin/ffmpeg
# Assists in relative path weirdness
reset=$(pwd)
error() {
	CODE=$1
	shift
	echo "Critical error:" "${@}"
	exit "$CODE"
}
usage() {
	cat <<EOF
    MediaHelper: Mass-apply cover art via ffmpeg
    -D:       Dry run, don't convert anything
    -i [dir]: Input directory
    -o [dir]: Output directory
    -h:       Show this help
    
    Experimental options:
    -e [ext]: Set file ext
    -E [ext]: Set input file ext (extra experimental)
EOF
	exit "$1"
}
while getopts "Dhi:o:e:E:" o; do
	case "${o}" in
	D) ffm="echo Dry run: ffmpeg " ;;
	i) SRCDIR=${OPTARG} ;;
	o) OUTDIR=${OPTARG} ;;
	e)
		OUTEXT=${OPTARG}
		SRCEXT=${OPTARG}
		;;
	E) SRCEXT=${OPTARG} ;;
	h) usage 0 ;;
	*) usage 2 ;;
	esac
done
shift $((OPTIND - 1))

mkdir -p "$OUTDIR"
# This cd-dance helps relative paths work
cd "$SRCDIR" || error 2 "cd to SRCDIR fail"
for i in *."$SRCEXT"; do
	y=${i%."$SRCEXT"}
	cd "$reset" || error 2 "cd to reset fail"
	$ffm \
		-i "$SRCDIR/$i" \
		-i "$SRCDIR/cover.png" \
		-c copy \
		-map 0 \
		-map 1 \
		"$OUTDIR/$y.$OUTEXT" || error 127 "FFMpeg exited badly!"
	cd "$reset" || error 2 "cd to reset fail"
	cd "$SRCDIR" || error 2 "cd to SRCDIR fail"
done