normvol

#!/usr/bin/env bash

# problem: my recorders often produce audio streams with volume level far lower than ideal
# ffmpeg (and bash and perl) to the rescue!  Catalyst https://superuser.com/questions/323119/how-can-i-normalize-audio-using-ffmpeg

# fork of tomp3normvol: this one works with .ogg files as well as .mp3 (output file has same format as input; to convert to mp3, use another script)

die() { printf %s "${@+$@$'\n'}" 1>&2 ; exit 1 ; }

command -v ffmpeg || die "ffmpeg not in PATH"

read_mean_volume_neg_db() (
   ffmpeg -i "$1" -vn -sn -dn -af "volumedetect" -f null /dev/null 2>&1 >/dev/null | perl -lne '/mean_volume: \-(\d+)\.\d+ dB/ && print $1'
   )

normvol_to_mp3() (
   # set -x

   fnm="$1"  # ; echo "fnm=$1'"
   [[ -f "$fnm" ]] || die "$fnm is not a file"

   # break down $fnm:
   fpath=""
   if [[ $fnm == */* ]]; then
      fpath="${fnm%/*}/"
      cd "$fpath" || die "cd to $fpath failed"
   fi                                   # ; echo "fpath=$fpath'"

   sanspath="${1##*/}"       #  ; echo "sanspath=$sanspath'"    # https://stackoverflow.com/a/965069
   ext="${sanspath##*.}"     #  ; echo "ext=$ext'"
   sansext="${sanspath%.*}"  #  ; echo "sansext=$sansext'"

   outfnm="${sansext}_normvol.$ext"
   [[ -f "$outfnm" && "$outfnm" -nt "$1" ]] && die "exists $outfnm"
   meanvol="$(read_mean_volume_neg_db "$1")" || die "read_mean_volume_neg_db failed on $1"
   dbadj=$(( meanvol / 2 ))
   printf "+%3ddB %s\n" "$dbadj" "$outfnm"
   if (( dbadj > 0 )); then
      ffmpeg -i "$1" -y -f "$ext" -q:a 0 -af "volume=${dbadj}dB" "$outfnm" 2> /dev/null || die "normvol failed on $1"
   fi
   )

for fnm in "$@"; do
   if [[ -f "$fnm" ]]; then
      case "$fnm" in
         *_normvol.*)  echo "!recnv $fnm" ;;
         *)            normvol_to_mp3 "$fnm" ;;
      esac
   fi
done