user/mp3s_to_opus.sh

   1 #!/bin/bash
   2 # Desc: Converts a directory of mp3s into a single opus file
   3 # Usage: mp3s_to_opus.sh [DIR in] [DIR out] [BITRATE]
   4 # Example: mp3s_to_opus.sh ./dir_source ./dir_output 48k
   5 # Depends: GNU Coretils 8.32 (date)
   6 # Version: 0.0.4
   7
   8 # plumbing
   9 opus_bitrate="$3"; # e.g. "48k"
  10 script_rundate="$(date +%s)";
  11 dir_tmp="/dev/shm";
  12 dir_in="$(readlink -f "$1")";
  13 dir_out="$(readlink -f "$2")";
  14 file_flist="$dir_tmp"/"$script_rundate"..flist.txt;
  15 file_out_opus="$dir_out"/output.opus;
  16 file_albumart="$dir_out"/albumart.png;
  17
  18 yell() { echo "$0: $*" >&2; } # print script path and all args to stderr
  19 die() { yell "$*"; exit 111; } # same as yell() but non-zero exit status
  20 must() { "$@" || die "cannot $*"; } # runs args as command, reports args if command fails
  21 show_usage() {
  22     # Desc: Display script usage information
  23     # Usage: showUsage
  24     # Version 0.0.2
  25     # Input: none
  26     # Output: stdout
  27     # Depends: GNU-coreutils 8.30 (cat)
  28     cat <<'EOF'
  29     USAGE:
  30         mp3s_to_opus.sh [DIR in] [DIR out] [BITRATE]
  31
  32     EXAMPLE:
  33       mp3s_to_opus.sh ./source_dir ./out_dir 48k
  34 EOF
  35 } # Display information on how to use this script.
  36 check_depends() {
  37     if ! command -v ffmpeg; then show_usage; die "FATAL:Missing ffmpeg."; fi;
  38 }; # check dependencies
  39 check_plumbing() {
  40     if [[ $# -ne 3 ]]; then show_usage; die "FATAL:Invalid arg count:$#"; fi;
  41     if [[ ! -d "$dir_in" ]]; then show_usage; die "FATAL:Not a dir:$dir_in"; fi;
  42     if [[ ! -d "$dir_out" ]]; then mkdir -p "$2"; fi;
  43 }; # check arguments
  44 build_filelist() {
  45     # Depends: var dir_tmp     temporary directory
  46     #          var dir_in      input dir
  47     #          var file_flist  path file list
  48     # Output: file: $file_flist  list of mp3 files for ffmpeg
  49
  50     # Change directory to input dir
  51     pushd "$dir_in" || die "FATAL:Directory error:$(pwd)";
  52
  53     while read -r line; do
  54         yell "$(printf "file '%s'\n" "${line#./}")";
  55         printf "file '%s'\n" "${line#./}" >> "$file_flist";
  56     done < <(find "$dir_in" -type f -iname "*.mp3" | sort);
  57
  58     # Return to original dir
  59     popd || die "FATAL:Directory error:$(pwd)";
  60
  61 }; # build file list for ffmpeg
  62 ffmpeg_convert() {
  63     # Depends: var dir_tmp
  64     #              dir_in
  65     #              dir_out
  66     # Input: file $file_flist  list of mp3 files for ffmpeg
  67
  68     # Change directory to input dir
  69     pushd "$dir_in" || die "FATAL:Directory error:$(pwd)";
  70
  71     # Concatenate mp3 files into a single WAV file
  72     #   # Convert WAV to 48 kbps opus file
  73     ffmpeg -nostdin -f concat -safe 0 -i "$file_flist" -c:a pcm_s24le -rf64 auto -f wav - | \
  74         ffmpeg -i - -c:a libopus -b:a "$opus_bitrate" "$file_out_opus";
  75
  76     # Return to original dir
  77     popd || die "FATAL:Directory error:$(pwd)";
  78 }; # convert mp3s to opus via ffmpeg
  79 save_albumart() {
  80     local file
  81     file="$(find "$dir_in" -type f -iname "*.mp3" | sort | head -n1)";
  82     file="$(readlink -f "$file")";
  83     ffmpeg -nostdin -i "$file" -an -vcodec copy "$file_albumart";
  84 }; # save album art from an mp3 to output dir
  85 main() {
  86     check_depends && yell "DEBUG:check_depends OK";
  87     check_plumbing "$@" && yell "DEBUG:check_plumbing OK";
  88     build_filelist "$@" && yell "DEBUG:build_filelist OK";
  89     ffmpeg_convert "$@" && yell "DEBUG:ffmpeg_convert OK";
  90     save_albumart "$@" && yell "DEBUG:save_albumart OK";
  91 }; # main program
  92
  93 main "$@";
  94