AAXtoMP3/AAXtoMP3

#!/usr/bin/env bash


# ========================================================================
# Command Line Options
usage=$'\nUsage: AAXtoMP3.sh [--flac] [--aac] [--opus ] [--single] [--authcode <AUTHCODE>]\n[--output_dir <PATH>] {FILES}\n'
codec=libmp3lame
extension=mp3
mode=chaptered
auth_code=
targetdir=

while true; do
  case "$1" in
    -f | --flac       ) codec=flac; extension=flac; shift ;;
    -a | --aac        ) codec=copy; extension=m4a; mode=single ;shift ;;
    -o | --opus       ) codec=libopus; extension=ogg; shift ;;
    -s | --single     ) mode=single; shift ;;
    -t | --target_dir ) targetdir="$2"; shift 2 ;;
    -A | --authcode   ) auth_code="$2"; shift 2 ;; 
    -d | --debug      ) DEBUG=1; shift ;;              # Not so secret flag for debug output.  to use in code  [ $DEBUG == 1 ] && sample=2
    -h | --help       ) printf "$usage" $0 ; exit ;;
    --                ) shift; break ;;
    *                 ) break ;;
  esac
done

if [ "$#" -eq 0 ]; then
  printf "$usage" $0
  exit 1
fi

# ========================================================================
# Variable validation
set -o errexit -o noclobber -o nounset -o pipefail

GREP=$(grep --version | grep -q GNU && echo "grep" || echo "ggrep")

if ! [[ $(type -P "$GREP") ]]; then
    echo "$GREP (GNU grep) is not in your PATH"
    echo "Without it, this script will break."
    echo "On macOS, you may want to try: brew install grep"
    exit 1
fi

# Obtain the authcode from either the command line,  local directory or home directory.
if [ -z $auth_code ]; then
  if [ -r .authcode ]; then
    auth_code=`head -1 .authcode`
  elif [ -r ~/.authcode ]; then
    auth_code=`head -1 ~/.authcode`
  fi
fi
if [ -z $auth_code ]; then
  echo "ERROR Missing authcode"
  echo "$usage"
  exit 1  
fi

# Check the target dir for if set if it is writable
if [[ ! -w "${targetdir}" || ! -d "${targetdir}" ]] ; then
  echo "ERROR Target Directory is not writable: \"$targetdir\""
  echo "$usage"
  exit 1 
fi

# ========================================================================
# Utility Functions

debug() {
    echo "$(date "+%F %T%z") ${1}"
}

trap 'rm -r -f "${working_directory}"' EXIT
working_directory=`mktemp -d 2>/dev/null || mktemp -d -t 'mytmpdir'`
metadata_file="${working_directory}/metadata.txt"

save_metadata() {
    local media_file
    media_file="$1"
    ffprobe -i "$media_file" 2> "$metadata_file"
}

get_metadata_value() {
    local key
    key="$1"
    normalize_whitespace "$($GREP --max-count=1 --only-matching "${key} *: .*" "$metadata_file" | cut -d : -f 2- | sed -e 's#/##g;s/ (Unabridged)//' | tr -s '[:blank:]' ' ')"
}

get_bitrate() {
    get_metadata_value bitrate | $GREP --only-matching '[0-9]\+'
}

normalize_whitespace() {
    echo $*
}

# ========================================================================
# Main Transcode Loop
for path
do
    debug "Decoding ${path} with auth code ${auth_code}..."

    # Check for Presense of Audiobook
    [ ! -r "${path}" ] && echo "ERROR: Input file $path missing" ; exit 1

    save_metadata "${path}"
    genre=$(get_metadata_value genre)
    artist=$(get_metadata_value artist)
    title=$(get_metadata_value title | sed 's/'\:'/'-\ '/g' | xargs -0)
    if [ ! -z targetdir ] ; then
      output_directory="${targetdir}/${genre}/${artist}/${title}"
    else
      output_directory="$(dirname "${path}")/${genre}/${artist}/${title}"
    fi
    mkdir -p "${output_directory}"
    full_file_path="${output_directory}/${title}.${extension}"

    # This is the primary transcode. All the heavy lifting is here.
    </dev/null ffmpeg -loglevel error -stats -activation_bytes "${auth_code}" -i "${path}" -vn -codec:a "${codec}" -ab "$(get_bitrate)k" -map_metadata -1 -metadata title="${title}" -metadata artist="${artist}" -metadata album_artist="$(get_metadata_value album_artist)" -metadata album="$(get_metadata_value album)" -metadata date="$(get_metadata_value date)" -metadata track="1/1" -metadata genre="${genre}" -metadata copyright="$(get_metadata_value copyright)" "${full_file_path}"

    debug "Created ${full_file_path}."

    # Grab the cover art if available.
    cover_path="${output_directory}/cover.jpg"

    debug "Extracting cover into ${cover_path}..."
    </dev/null ffmpeg -loglevel error -activation_bytes "${auth_code}" -i "${path}" -an -codec:v copy "${cover_path}"    

    # If we want multiple file we take the big mp3 and split it by chapter.
    if [ "${mode}" == "chaptered" ]; then
        # Playlist m3u support
        playlist_file="${output_directory}/${title}.m3u"
        debug "Creating PlayList ${title}.m3u"
        echo '#EXTM3U' > "${playlist_file}"

        chaptercount=$($GREP -Pc "Chapter.*start.*end" $metadata_file)
        debug "Extracting ${chaptercount} chapter files from ${full_file_path}..."

        chapternum=1
        while read -r -u9 first _ _ start _ end
        do
            if [[ "${first}" = "Chapter" ]]
            then
                read -r -u9 _
                read -r -u9 _ _ chapter
                chapter_title="${title} - $(printf %0${#chaptercount}d $chapternum) ${chapter}"
                chapter_file="${output_directory}/${chapter_title}.${extension}"
                
                # the ID3 tags must only be specified for *.mp3 files,
                # the other container formats come with their own
                # tagging mechanisms.
                id3_version_param=""
                if test "${extension}" = "mp3"; then
                   id3_version_param="-id3v2_version 3"
                fi

                </dev/null ffmpeg -loglevel error -stats -i "${full_file_path}" -i "${cover_path}" -ss "${start%?}" -to "${end}" -map 0:0 -map 1:0 -acodec copy ${id3_version_param} \
                    -metadata:s:v title="Album cover" -metadata:s:v comment="Cover (Front)" -metadata track="${chapternum}" -metadata title="${chapter_title}" \
                    "${chapter_file}"
                
                duration=$(echo "${end} - ${start%?}" | bc)
                echo "#EXTINF:${duration%.*},${title} - ${chapter}" >>  "${playlist_file}"
                echo "${chapter_title}.${extension}" >> "${playlist_file}"
                chapternum=$((chapternum + 1 ))
            fi
        done 9< "$metadata_file"
        rm "${full_file_path}"
        debug "Done creating chapters. Chaptered files contained in ${output_directory}."
    fi

    debug "Done."
    rm "${metadata_file}"
done