#!/usr/bin/env bash

# Use this to normalize the volume of a video or audio file using the average loudness, or RMS-based normalization. It does a pretty good job!
# If you want to modify the volume manually then checkout the analyze-volume and change-volume scripts.
#
# This does not re-encode video when given a video file.
#
# Inspired by https://superuser.com/a/323127 and https://superuser.com/a/1312885

if which tput >/dev/null 2>&1; then
    ncolors=$(tput colors)
fi
if [ -t 1 ] && [ -n "$ncolors" ] && [ "$ncolors" -ge 8 ]; then
    RED="$(tput setaf 1)"
    GREEN="$(tput setaf 2)"
    YELLOW="$(tput setaf 3)"
    BLUE="$(tput setaf 4)"
    MAGENTA="$(tput setaf 5)"
    CYAN="$(tput setaf 6)"
    BOLD="$(tput bold)"
    NORMAL="$(tput sgr0)"
else
    RED=""
    GREEN=""
    YELLOW=""
    BLUE=""
    MAGENTA=""
    CYAN=""
    BOLD=""
    NORMAL=""
fi

if [[ $1 == "" ]]; then
    printf "${BOLD}${RED}Usage: normalize-volume <video or audio filename> <optional output name>${NORMAL}\n"
    exit 1
fi

filename=$(basename -- "$1")
extension="${filename##*.}"
filename="${filename%.*}"

output_name="$2"

if [[ $output_name == "" ]]; then
    output="${filename}_normalized_audio.$extension"
else
    output="${output_name}.$extension"
fi

printf "\n${YELLOW}${BOLD}Normalizing audio in $filename.$extension | output: $output${NORMAL}\n"

# This is done in two passes. The first pass will compute the mean loudness and
# the second pass will normalize the audio using the mean as the target.

temp_file="/tmp/_audio_info_$RANDOM"

# 1st pass:
cmd="ffmpeg -i \"$filename.$extension\" -pass 1 -filter:a loudnorm=print_format=json -vn -sn -dn -f null /dev/null 2>&1 | sed -n '/{/,/}/p' > $temp_file"
printf "\n${BOLD}Running 1st pass:\n$cmd\n\n${NORMAL}"
eval "$cmd"

printf "${BOLD}${GREEN}Done.\n\n${NORMAL}"

ii=`grep   \"input_i\"       $temp_file | cut -d: -f2 | tr -cd [:digit:].-`
itp=`grep  \"input_tp\"      $temp_file | cut -d: -f2 | tr -cd [:digit:].-`
ilra=`grep \"input_lra\"     $temp_file | cut -d: -f2 | tr -cd [:digit:].-`
it=`grep   \"input_thresh\"  $temp_file | cut -d: -f2 | tr -cd [:digit:].-`
to=`grep   \"target_offset\" $temp_file | cut -d: -f2 | tr -cd [:digit:].-`

# 2nd pass:
cmd="ffmpeg -y -stats -loglevel level+error -i \"$filename.$extension\" -c:v copy -pass 2 -filter:a loudnorm=linear=true:I=-16:LRA=11:tp=-1.5:measured_I=$ii:measured_LRA=$ilra:measured_tp=$itp:measured_thresh=$it:offset=$to:print_format=summary \"$output\""
printf "${BOLD}Re-encoding audio:\n$cmd\n\n${NORMAL}"
eval "$cmd"

printf "\n${GREEN}${BOLD}Done normalizing volume in $filename.$extension | output: $output${NORMAL}\n"
rm $temp_file