tomp3

#! /bin/sh

FORMATS_TO_BE_CONVERTED="flac|m4a|aac" # seperate by |

if [ "$1" = "--help" ] || [ "$1" = "-h" ] || [ "$1" = "help" ]; then
  cat << EOF
$ tomp3 DIR
Recursively convert to mp3

format that are converted: $FORMATS_TO_BE_CONVERTED

Parameters:
  \$1: directory to be converted
EOF
  exit
fi

command -v ffmpeg >/dev/null || { echo "ffmpeg is not installed"; exit 127; }

DIR="$1"
[ -z "$1" ] && DIR="."

COUNT=$(mktemp)

find "$DIR" -regextype posix-egrep -type f -regex ".*\.($FORMATS_TO_BE_CONVERTED)" -exec sh -c \
  'echo "converting $1"; echo "$1" >>'$COUNT'; ffmpeg -loglevel error -nostdin -i "$1" -ab 320k "${1%.*}".mp3' sh {} ';'
# src: https://unix.stackexchange.com/a/428414

# maybe "-c:a libmp3lame -b:a 320k" if 320 does not work

if [ -s "$COUNT" ]; then
  COUNT_CONVERTED=$(wc -l <$COUNT)
  COUNT_CURRENT_FILE=$(mktemp)
  find "$DIR" -regextype posix-egrep -type f -regex ".*\.($FORMATS_TO_BE_CONVERTED)" >$COUNT_CURRENT_FILE
  COUNT_CURRENT=$(wc -l <$COUNT_CURRENT_FILE)
  if [ "$COUNT_CONVERTED" != "$COUNT_CURRENT" ]; then
    echo "[WARN] discrepancy between the number of converted files vs current matched files."
    echo "  it is advised to rerun the script."
    printf "diff: "
    diff $COUNT $COUNT_CURRENT_FILE
    printf "continue? (y/N): "
    read con
    [ "$ans" != "y" ] && exit 0
  fi

  printf "remove source files? (y/N): "
  read ans
  [ "$ans" = "y" ] && find "$DIR" -regextype posix-egrep -type f -regex ".*\.($FORMATS_TO_BE_CONVERTED)" -exec sh -c 'rm "$1"' sh {} ';'
fi