Modified version of Lily's script to convert music files from flac to opus <3

flac-to-opus.sh

#!/usr/bin/env bash
set -euo pipefail

### ─── CONFIG ───────────────────────────────────────────────────────────────
INPUT_DIR="/home/julia/Music"
OUTPUT_DIR="/home/julia/MusicOpus"
HASH_FILE="$OUTPUT_DIR/.converted_hashes.txt"
COVER_HASH_FILE="$OUTPUT_DIR/.cover_hashes.txt"
LOG_FILE="$OUTPUT_DIR/conversion.log"
BITRATE="128"     # opusenc bitrate in kbps
MAX_JOBS=$(nproc) # parallel jobs
### ─────────────────────────────────────────────────────────────────────────

# TODO: some conversions are still unsuccessful
# Check `fd -e flac | wc -l` against `fd -e opus | wc -l`

# prepare
mkdir -p "$OUTPUT_DIR"
touch "$HASH_FILE" "$COVER_HASH_FILE" "$LOG_FILE"

# tee all output into the log as well
exec > >(tee -a "$LOG_FILE") 2>&1

echo "===== Starting batch at $(date) ====="

# sanitize for filesystem
sanitize() {
	echo "$1" |
		tr '/\\?%*:|"<>.' '_' |
		sed 's/[[:space:]]*$//'
}

artist_substitutions() {
	echo "$1" |
		sed 's/REN/Ren/' |
		sed 's/Kyteman Orchestra, The/Kyteman Orchestra/'
}

convert_one() {
	local flac="$1"
	echo "→ Processing: $flac"

	# 1) compute and check FLAC hash
	local hash
	hash=$(sha256sum "$flac" | cut -d' ' -f1)
	if grep -Fxq "$hash" "$HASH_FILE"; then
		echo "  • Already converted, skipping."
		return
	fi

	local album_dir
	album_dir=$(dirname "$flac")

	local dest_dir=${album_dir//$INPUT_DIR/$OUTPUT_DIR}
	dest_dir=$(echo "$dest_dir" | sed 's/\[.*FLAC.*\]/\[OPUS\]/')
	mkdir -p "$dest_dir"

	# 5) convert to opus with embedded tags
	local out="$dest_dir/$(basename "${flac%.flac}.opus")"
	echo "  • Converting → $out"

	# Get existing albumartist and artist
	album_artist=$(ffprobe -v quiet -show_entries format_tags=album_artist -of csv=p=0 "$flac")
	artist=$(ffprobe -v quiet -show_entries format_tags=artist -of csv=p=0 "$flac")

	# If no albumartist exists, use artist
	if [ -z "$album_artist" ]; then
		ffmpeg -i "$flac" -c:a libopus -b:a 128k -map_metadata 0 -metadata album_artist="$artist" "$out"
	else
		ffmpeg -i "$flac" -c:a libopus -b:a 128k -map_metadata 0 "$out"
	fi

	# 6) copy any cover art from the FLAC folder
	local src_dir
	src_dir=$(dirname "$flac")
	find "$src_dir" -maxdepth 1 -type f \( -iname '*.jpg' -o -iname '*.jpeg' -o -iname '*.png' \) |
		while IFS= read -r img; do
			local img_hash
			img_hash=$(sha256sum "$img" | cut -d' ' -f1)
			if grep -Fxq "$img_hash" "$COVER_HASH_FILE"; then
				echo "  • Cover already copied: $(basename "$img")"
			else
				echo "  • Copying cover: $(basename "$img")"
				cp "$img" "$dest_dir/"
				echo "$img_hash" >>"$COVER_HASH_FILE"
			fi
		done
	# if no external image was found, try extracting embedded art
	if ! grep -q "^CoverCopied:" <<<"$dest_dir"; then
		# dump the first embedded picture, if any
		# metaflac will error out if there’s no picture, so we redirect stderr
		if metaflac --export-picture-to=- "$flac" 2>/dev/null |
			file --brief --mime-type - | grep -qE '^(image/(jpeg|png))$'; then
			ext=$(metaflac --list --block-type=PICTURE "$flac" |
				grep MIME-type | head -n1 | cut -d' ' -f2 | sed 's#image/##')
			outimg="$dest_dir/cover.${ext:-jpg}"
			echo "  • Extracting embedded cover → $(basename "$outimg")"
			metaflac --export-picture-to="$outimg" "$flac"
			# record hash so we don’t do it twice
			sha256sum "$outimg" | cut -d' ' -f1 >>"$COVER_HASH_FILE"
		fi
	fi

	# 7) record FLAC hash
	echo "$hash" >>"$HASH_FILE"
	echo "  ✔ Done."
}

export -f convert_one sanitize artist_substitutions
export INPUT_DIR OUTPUT_DIR HASH_FILE COVER_HASH_FILE BITRATE

# 8) find & parallelize
find "$INPUT_DIR" -type f -iname '*.flac' -print0 |
	xargs -0 -n1 -P"$MAX_JOBS" bash -c 'convert_one "$0"'

echo "===== Batch finished at $(date) ====="