Encode flac files to opus preserving folder structure and stripping ID3 tags

flac2opus.sh

#!/bin/bash

# Copyright 2019 Bertrand Michas <berturion@free.fr>
#
# Permission to use, copy, modify, and/or distribute this software for any
# purpose with or without fee is hereby granted, provided that the above
# copyright notice and this permission notice appear in all copies.
#
# THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCNUMBERLAIMS ALL WARRANTIES WITH
# REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
# AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
# INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
# LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
# OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
# PERFORMANCE OF THIS SOFTWARE.

# "global" variables
USER=$(whoami)
SCRIPT=`realpath $0`
SCRIPT_FILE_NAME=`basename $0`
DIR=`dirname $SCRIPT`
DATEEXEC=`date "+%Y/%m/%d %T"`

# params related variables
ID3_STRIP_ACTION=0
REMOVE_EXISTING_ACTION=0
INPUT_FOLDER=""
OUTPUT_FOLDER=""
BITRATE=0
MIN_BITRATE=16
MAX_BITRATE=192
N=1
MIN_JOBS=1
MAX_JOBS=32

function usage {
	cat <<EOF


HELP for $SCRIPT_FILE_NAME:
------------
This script can do multiple actions on flac files.
- Collect all flac files found recursively in a folder to a file
- Remove any ID3 tags in place (ID3 tags are invalid for flac files).
This action modifies the files but preserve all metatada.
- Encode all flac files found into the "input_folder" to the
"output_folder", folder structure is preserved.
- Delete opus encoded target files if exist

Usage: $SCRIPT_FILE_NAME -i input_folder [options]

Options:
	-h	Show help
	-i	[required] "input_folder": input folder containing flac
		files.
	-c	[optional] "clear_id3": clear all ID3 tags from flac
		files preserving metadata (ID3 tags for flac files are invalid).
	-o	[optional] "output_folder": output folder where encoded opus
		files will be stored. Required with options "-d" or "-b".
	-d	[optional] "delete_existing": delete existing opus files
		in output_folder.
	-b	[optional] "bitrate": encode flac files from "input_folder"
		to opus files into the "output_folder" with the specified vbr
		bitrate. Must be between $MIN_BITRATE and $MAX_BITRATE.
		Encoding will fail if an ID3 tag is present or if the opus
		encoded file already exists.
	-j	[optional] "jobs": number of parallel jobs. Between
		$MIN_JOBS and $MAX_JOBS. Default $N.

Examples :
	'$SCRIPT_FILE_NAME -i "path/to/flacs/" -o "path/to/opus/" -d -c -b 96 -j 4
	'$SCRIPT_FILE_NAME -h'

Requirements :
	flac, opus-tools, id3v2

EOF
}

which metaflac >> /dev/null
if [ $? -ne 0 ]; then
	echo "flac tools are not installed. Run \`sudo pacman -S flac\` and try again."
	exit 1
fi
which opusenc >> /dev/null
if [ $? -ne 0 ]; then
	echo "opus-tools is not installed. Run \`sudo pacman -S opus-tools\` and try again"
	exit 1
fi
which id3v2 >> /dev/null
if [ $? -ne 0 ]; then
	echo "id3v2 is not installed. Run \`sudo pacman -S id3v2\` and try again"
	exit 1
fi

# test that argument is a folder
# if this is not a folder, returns an empty string
# adds a trailing slash if missing
sanitize_folder() {
	local folder="$1"
	if [ -z "$1" ]; then
		folder=""
	elif [ ! -d $1 ]; then
		folder=""
	elif [[ ! "$1" == */ ]];then
		folder="$folder/"
	fi
	echo $folder
}

while getopts "hi:co:edb:j:" opt; do
	case $opt in
		h)
			usage
			exit 0
			;;
		i)
			# INPUT_FOLDER=`realpath $OPTARG`
			INPUT_FOLDER=`sanitize_folder "$OPTARG"`
			if [ ! -d "$INPUT_FOLDER" ];then
				echo "-i \"$OPTARG\" is not a folder"
				echo "Call '$SCRIPT_FILE_NAME -h' to see usage"
				exit 1
			fi
			if [ ! -w "$INPUT_FOLDER" ];then
				echo "-i \"$OPTARG\" is not writable"
				echo "Call '$SCRIPT_FILE_NAME -h' to see usage"
				exit 1
			fi
			;;
		c)
			ID3_STRIP_ACTION=1
			;;
		o)
			# OUTPUT_FOLDER=`realpath $OPTARG`
			OUTPUT_FOLDER=`sanitize_folder $OPTARG`
			if [ ! -d "$OUTPUT_FOLDER" ];then
				echo "-o \"$OPTARG\" is not a folder"
				echo "Call '$SCRIPT_FILE_NAME -h' to see usage"
				exit 1
			fi
			if [ ! -w "$OUTPUT_FOLDER" ];then
				echo "-o \"$OPTARG\" is not writable"
				echo "Call '$SCRIPT_FILE_NAME -h' to see usage"
				exit 1
			fi
			;;
		d)
			REMOVE_EXISTING_ACTION=1
			;;
		b)
			BITRATE=$(sed 's/[^0-9]//g' <<< $OPTARG)
			if [ -z $BITRATE ]; then
				echo "-b \"$OPTARG\" invalid bitrate"
				echo "Call '$SCRIPT_FILE_NAME -h' to see usage"
				exit 1
			fi
			if [ $BITRATE -gt $MAX_BITRATE ]; then
				echo "-b \"$OPTARG\" greater than $MAX_BITRATE"
				echo "Call '$SCRIPT_FILE_NAME -h' to see usage"
				exit 1
			fi
			if [ $BITRATE -lt $MIN_BITRATE ]; then
				echo "-b \"$OPTARG\" lesser than $MIN_BITRATE"
				echo "Call '$SCRIPT_FILE_NAME -h' to see usage"
				exit 1
			fi
			;;
		j)
			N=$(sed 's/[^0-9]//g' <<< $OPTARG)
			if [ -z $N ]; then
				echo "-j \"$OPTARG\" invalid number of jobs"
				echo "Call '$SCRIPT_FILE_NAME -h' to see usage"
				exit 1
			fi
			if [ $N -lt $MIN_JOBS ]; then
				echo "-j \"$OPTARG\" lesser than $MIN_JOBS"
				echo "Call '$SCRIPT_FILE_NAME -h' to see usage"
				exit 1
			fi
			if [ $N -gt $MAX_JOBS ]; then
				echo "-j \"$OPTARG\" greater than $MAX_JOBS"
				echo "Call '$SCRIPT_FILE_NAME -h' to see usage"
				exit 1
			fi
			;;
		\?)
			echo "Invalid option: -$OPTARG"
			echo "Call '$SCRIPT_FILE_NAME -h' to see usage"
			;;
		:)
			echo "Option -$OPTARG requires an argument."
			echo "Call '$SCRIPT_FILE_NAME -h' to see usage"
			exit 1
			;;
	esac
done

# Handle missing required params
if [ -z $OUTPUT_FOLDER ] ; then
	if [ $BITRATE -gt 0 ] ; then
		echo "Output folder is required to encode the files"
		echo "Call '$SCRIPT_FILE_NAME -h' to see usage"
		exit 1
	fi
	if [ $REMOVE_EXISTING_ACTION -gt 0 ] ; then
		echo "Output folder is required to remove existing encoded files"
		echo "Call '$SCRIPT_FILE_NAME -h' to see usage"
		exit 1
	fi
fi

echo "Enabled actions:"
echo "- Collect flac files"
if [ $BITRATE -gt 0 ];then
	echo "- Encode with a bitrate of $BITRATE"
fi
if [ $REMOVE_EXISTING_ACTION -gt 0 ];then
	echo "- Remove encoded existing encoded file"
fi
if [ $ID3_STRIP_ACTION -gt 0 ];then
	echo "- Strip ID3 tags from flac files"
fi
echo "Parameters:"
echo "- Input folder: $INPUT_FOLDER"
echo "- Output folder: $OUTPUT_FOLDER"
echo "- Number of parallel jobs: $N"

COLLECTED_FLAC_FILES_FILE="${INPUT_FOLDER}collected_flac_files.txt"
rm -f "$COLLECTED_FLAC_FILES_FILE"

# Process flac file with chosen actions
# params:
# - "$1" : input flac file
process_flac() {
	flac_file="$1"
	echo "Processing $flac_file"
	if [[ "$flac_file" == *.flac ]];then
		if [ $ID3_STRIP_ACTION -eq 1 ];then
			head_bytes=`dd if="$flac_file" of=/dev/stdout bs=1 count=3 2>/dev/null`
			if [ "$head_bytes" = "ID3" ];then
				echo "Invalid ID3 tag in this .flac file."
				metaflac_file="${flac_file}.metaflac"
				# Remove invalid ID3 tag from flac file
				metaflac --export-tags-to="$metaflac_file" "$flac_file"
				id3v2 -D "$flac_file"
				metaflac --remove-all-tags --import-tags-from="$metaflac_file" "$flac_file"
				rm "$metaflac_file"
			fi
		fi

		new_file="${1/$INPUT_FOLDER/$OUTPUT_FOLDER}"
		new_file="${new_file/%flac/opus}"
		new_folder="$(dirname "$new_file")"
		if [[ -f "$new_file" ]] && [[ $REMOVE_EXISTING_ACTION -eq 1 ]]; then
			rm -v "$new_file"
		fi
		if [ $BITRATE -gt 0 ];then
			if [ ! -f "$new_file" ]; then
				mkdir -p "$new_folder" && opusenc --vbr --bitrate "$BITRATE" "$flac_file" "$new_file" 2> /dev/null
				if [ $? -gt 0 ] ; then
					echo "Error encoding $flac_file"
				else
					echo "Encoded into $new_file"
				fi
			else
				echo "Encoded file already exists: $new_file"
			fi
		fi
	fi
}

# Recursive walk through directories and put each flac file found into
# "$COLLECTED_FLAC_FILES_FILE" file
recurse_conv() {
	for i in "$1"/* ; do
		if [ -d "$i" ];then
				recurse_conv "$i"
		elif [ -f "$i" ]; then
				found_file="$i"
				if [[ $found_file == *.flac ]];then
					NB_FLAC_FILES=$NB_FLAC_FILES+1
					echo $found_file >> "$COLLECTED_FLAC_FILES_FILE"
				fi
		fi
	done
}

# @see https://unix.stackexchange.com/questions/103920/parallelize-a-bash-for-loop
open_sem(){
	mkfifo pipe-$$
	exec 3<>pipe-$$
	rm pipe-$$
	local i=$1
	for((;i>0;i--)); do
		printf %s 000 >&3
	done
}

run_with_lock(){
	local x
	read -u 3 -n 3 x && ((0==x)) || exit $x
	(
	 ( "$@"; )
	printf '%.3d' $? >&3
	)&
}

echo "Recursive flac collection into $COLLECTED_FLAC_FILES_FILE"
# Removing all trailing slashes before recursive loop in folders
TMP_INPUT_FOLDER=`echo "$INPUT_FOLDER" | sed 's/\/*$//'`
recurse_conv "$TMP_INPUT_FOLDER"

if [[ $BITRATE -gt 0 ]] || [[ $REMOVE_EXISTING_ACTION -gt 0 ]] || [[ $ID3_STRIP_ACTION -gt 0 ]]; then
	echo "Parallel processing"
	open_sem $N
	while read p; do
		run_with_lock process_flac "$p"
	done <"$COLLECTED_FLAC_FILES_FILE"
fi
# wait until all parallel jobs are finished
wait

echo "Done"

exit 0