A script to convert cover artwork on *.m4a files to be compatible with Rockbox. Use at your own risk

M4Artwork.sh

#!/bin/bash

clear

# Finds all m4a files, and loops through them while assigning the file name to "$f"
find . -type f -name '*.m4a' -exec sh -c '

for f do

	echo "$f"
	echo "Extracting Artwork..."
	# Extracts the album artwort to "$f".jpg (baseline)
	ffmpeg -i "$f" -map 0:1 "$f".jpg -v quiet > output.txt

	echo "Removing old artwork..."
	# Strips the embedded album art
	mp4art --remove "$f" > output.txt

	echo "Resizing new artwork..."
	# Resizes "$f".jpg
	sips -Z 800 "$f".jpg > output.txt

	echo "Embedding new artwork..."
	# Embeds album art back into "$f"
	mp4art --add "$f".jpg "$f" > output.txt
	echo "Done!"
	echo
	echo
	rm "$f".jpg
	sleep 1
done' sh {} +
echo
echo "Done, enjoy!"

exit 0