Convert FLAC to M4A (AAC/ALAC) with ffmpeg

ConvertFlacToM4A.sh

#!/bin/bash
#
# Convert FLAC to M4A with ffmpeg
# Usage: convert_music.sh source_dir destination_dir
# Requires: ffmpeg - https://ffmpeg.org/download.html
#
# Author: Rick Makes - https://www.rickmakes.com/batch-convert-lossless-audio-to-aac-shell-script/
# Modified: Anthony Hortin
#

set -e # exit script if control-c is used
USAGE="Usage: sh ConvertFlacToM4A.sh source_dir destination_dir"

# --- Options processing -------------------------------------------
if [ $# == 0 ] ; then
	echo $USAGE
	exit 1;
fi

# Convert relative path to absolute. Also remove trailing slash
SOURCE_DIR="$(cd "$(dirname "$1")"; pwd)/$(basename "$1")"
SOURCE_DIR=$(dirname "$SOURCE_DIR/temp") # this fixes . and ./
DESTINATION_DIR="$(cd "$(dirname "$2")"; pwd)/$(basename "$2")"
DESTINATION_DIR=$(dirname "$DESTINATION_DIR/temp") # this fixes . and ./
echo "Converting from: "$SOURCE_DIR
echo "Converting TO:   "$DESTINATION_DIR

find "$SOURCE_DIR" \( -iname '*.flac' -or -iname '*.m4a' \) -type f -print | while read -r FILE
do
	ORIG_DIR=$(dirname "$FILE")
	# Get basename and remove extension
	BASE=$(basename "$FILE") # get filename
	BASE=${BASE%.*} # remove extension from filename
	NEW_DIR=${ORIG_DIR/$SOURCE_DIR/$DESTINATION_DIR}
	mkdir -p "$NEW_DIR"
	NEW_FILE="$NEW_DIR/$BASE.m4a"
	if [ ! -f "$NEW_FILE" ]; then
		echo "Converting $FILE to $NEW_FILE"
		# Uncomment whichever is your preferred method below
		# AAC Lossy Compression
		#ffmpeg -hide_banner -i "$FILE" -c:a aac -vn -b:a 320k "$NEW_FILE" </dev/null
		# ALAC Lossless Compression
		ffmpeg -hide_banner -i "$FILE" -c:a alac -vn -b:a 1000k "$NEW_FILE" </dev/null
	fi
done