Reencode all FLAC audio files in a source directory into OPUS and output them into a destination directory

flac2opus.sh

#!/usr/bin/env bash

# ============================================================================= #
# Copyright © 2025 Guiorgy                                                      #
#                                                                               #
# This program is free software: you can redistribute it and/or modify it under #
# the terms of the GNU General Public License as published by the Free Software #
# Foundation, either version 3 of the License, or (at your option) any later    #
# version.                                                                      #
#                                                                               #
# This program is distributed in the hope that it will be useful, but WITHOUT   #
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS #
# FOR A PARTICULAR PURPOSE.                                                     #
#                                                                               #
# You can see the full GNU General Public License at                            #
# <https://www.gnu.org/licenses/> for more details.                             #
# ============================================================================= #

set -eu

SOURCE="${1-}"
DESTINATION="${2-}"

if [[ -z "$SOURCE" || -z "$DESTINATION" ]]; then
  cat >&2 <<EOF
Source ('$SOURCE') and destination ('$DESTINATION') must not be empty"

Usage: $(basename "$0") source destination
EOF
  exit 1
fi

convert_flac_to_opus() {
  flac="$1"
  dest="$2"
  opus="${dest%/}/$(basename "$flac" '.flac').opus"

  ffmpeg \
    -y \
    -i "$flac" \
    -c:a libopus -b:a 128k \
    -compression_level 10 -frame_duration 60 -threads 1 \
    -map 0:a -map_metadata 0 -id3v2_version 3 \
    "$opus"
}
export -f convert_flac_to_opus

find "$SOURCE" -maxdepth 1 -name '*.flac' -print0 \
  | xargs -0 -n 1 -P "$(nproc)" -I {} sh -c 'convert_flac_to_opus "$1" "$2"' -- {} "$DESTINATION"