normalize

#!/bin/sh

# normalize audio levels

# script usage
usage()
{
echo "\
# normalize audio levels

$(basename "$0") -i infile.(mp4|mkv|mov|m4v|aac|m4a|wav|mp3) -o outfile.(mp4|mkv|mov|m4v|aac|m4a|wav|mp3)
-i infile.(mp4|mkv|mov|m4v|aac|m4a|wav|mp3)
-o outfile.(mp4|mkv|mov|m4v|aac|m4a|wav|mp3) :optional agument 
# if option not provided defaults to infile-name-normalized-date-time-extension"
exit 2
}

# error messages
NOTFILE_ERR='not a file'
INVALID_OPT_ERR='Invalid option:'
REQ_ARG_ERR='requires an argument'
WRONG_ARGS_ERR='wrong number of arguments passed to script'
NOT_MEDIA_FILE_ERR='is not a media file'

# if script is run arguments pass and check the options with getopts,
# else display script usage and exit
[ $# -gt 0 ] || usage "${WRONG_ARGS_ERR}"

# getopts check and validate options
while getopts ':i:o:h' opt
do
  case ${opt} in
     i) infile="${OPTARG}"
	[ -f "${infile}" ] || usage "${infile} ${NOTFILE_ERR}";;
     o) outfile="${OPTARG}";;
     h) usage;;
     \?) usage "${INVALID_OPT_ERR} ${OPTARG}" 1>&2;;
     :) usage "${INVALID_OPT_ERR} ${OPTARG} ${REQ_ARG_ERR}" 1>&2;;
  esac
done
shift $((OPTIND-1))

# infile, infile name
infile_nopath="${infile##*/}"
infile_name="${infile_nopath%.*}"
infile_ext="${infile##*.}"

# file command check input file mime type
filetype="$(file --mime-type -b "${infile}")"

# audio and video mimetypes
mov_mime='video/quicktime'
mkv_mime='video/x-matroska'
mp4_mime='video/mp4'
m4v_mime='video/x-m4v'
wav_mime='audio/x-wav'
audio_mime='audio/mpeg'
aac_mime='audio/x-hx-aac-adts'
m4a_mime='audio/mp4'

# the file command wrongly identifies .m4a audio as a video file
# so we check if the file extension is .m4a and set the mime type to audio/mp4
if [ "${infile_ext}" = 'm4a' ]; then
    filetype="${m4a_mime}"
fi

# check the files mime type
case "${filetype}" in
    ${mov_mime}|${mkv_mime}|${mp4_mime}|${m4v_mime}| \
    ${wav_mime}|${audio_mime}|${aac_mime}|${m4a_mime});;
    *) usage "${infile} ${NOT_MEDIA_FILE_ERR}";;
esac

# print analyzing file
echo '+ Analyzing file with ffmpeg'

# ffmpeg loudnorm get stats from file
normalize=$(ffmpeg \
-hide_banner \
-i "${infile}" \
-af "loudnorm=I=-16:dual_mono=true:TP=-1.5:LRA=11:print_format=summary" \
-f null - 2>&1 | tail -n 12)

# read the output of normalize line by line and store in variables
for line in "${normalize}"; do
    measured_I=$(echo "${line}" | awk -F' ' '/Input Integrated:/ {print $3}')
    measured_TP=$(echo "${line}" | awk -F' ' '/Input True Peak:/ {print $4}')
    measured_LRA=$(echo "${line}" | awk -F' ' '/Input LRA:/ {print $3}')
    measured_thresh=$(echo "${line}" | awk -F' ' '/Input Threshold:/ {print $3}')
    offset=$(echo "${line}" | awk -F' ' '/Target Offset:/ {print $3}')
done

# defaults for variables if not defined
audio_default="${infile_name}-normalized-$(date +"%Y-%m-%d-%H-%M-%S").${infile_ext}"
video_default="${infile_name}-normalized-$(date +"%Y-%m-%d-%H-%M-%S").mp4"

# audio function
audio () {
    ffmpeg \
    -hide_banner \
    -stats -v panic \
    -i "${infile}" \
    -filter_complex \
    "loudnorm=I=-16:
    dual_mono=true:
    TP=-1.5:
    LRA=11:
    measured_I=${measured_I}:
    measured_LRA=${measured_LRA}:
    measured_TP=${measured_TP}:
    measured_thresh=${measured_thresh}:
    offset=${offset}:
    linear=true:
    print_format=summary [audio]" \
    -map "[audio]" \
    -ar 44100 \
    "${outfile:=${audio_default}}"
}

# video function
video () {
    ffmpeg \
    -hide_banner \
    -stats -v panic \
    -i "${infile}" \
    -c:v copy \
    -filter_complex \
    "loudnorm=I=-16:
    dual_mono=true:
    TP=-1.5:
    LRA=11:
    measured_I=${measured_I}:
    measured_LRA=${measured_LRA}:
    measured_TP=${measured_TP}:
    measured_thresh=${measured_thresh}:
    offset=${offset}:
    linear=true:
    print_format=summary [audio]" \
    -map 0:v -map "[audio]" \
    -ar 44100 \
    -pix_fmt yuv420p \
    -movflags +faststart \
    -f mp4 \
    "${outfile:=${video_default}}"
}

# check if the mime type is audio or video then run the correct function
case "${filetype}" in
    ${mov_mime}|${mkv_mime}|${mp4_mime}|${m4v_mime}) video "${infile}";;
    ${wav_mime}|${audio_mime}|${aac_mime}|${m4a_mime}) audio "${infile}";;
    *) usage "${infile} ${NOT_MEDIA_FILE_ERR}";;
esac