Normalizes the audio of an input file into an output file.

normalize.sh

#!/bin/bash
# Normalizes the audio of the input to the output.

if [ "$1" = "-h" ]; then
        echo "Normalizes the audio of the input into the output."
        echo "normalize.sh [input] [output=normalized.ext]"
        exit 0
fi

normalize() {

tempFile="$(mktemp)"
output="normalized"

if [ "$2" != "" ]; then
        output="$2"
        echo "Normalizing $1 to $2"
else
        filename=$(basename -- "$1")
        extension="${filename##*.}"
        output="$output.$extension"
        echo "$2 -- $filename -- $extension -- $output"
        echo "Converting $1 using the default filename $output"
fi

echo "Getting audio information..."
ffmpeg -i "$1" -af loudnorm=I=-16:TP=-1.5:LRA=11:print_format=summary -f null - 2> $tempFile

integrated="$(cat $tempFile | grep 'Input Integrated:' | grep -oP '[-+]?[0-9]+.[0-9]')"
truepeak="$(cat $tempFile | grep 'Input True Peak:' | grep -oP '[-+]?[0-9]+.[0-9]')"
lra="$(cat $tempFile | grep 'Input LRA:' | grep -oP '[-+]?[0-9]+.[0-9]')"
threshold="$(cat $tempFile | grep 'Input Threshold:' | grep -oP '[-+]?[0-9]+.[0-9]')"

echo "Integrated = $integrated :: True Peak = $truepeak :: LRA = $lra :: Threshold = $threshold"

echo "Re-encoding using audio analysis..."
ffmpeg -i "$1" -loglevel panic -af loudnorm=I=-16:TP=-1.5:LRA=11:measured_I=$integrated:measured_TP=$truepeak:measured_LRA=$lra:measured_thresh=$threshold:offset=-0.3:linear=true:print_format=summary "$output"

echo "Cleaning up..."
rm $tempFile

echo "Done! $output has been normalized."
}

if [ -d "$1" ]; then
        echo "Converting directory $1..."
        SAVEIFS=$IFS
        IFS=$(echo -en "\n\b")
        for fullfilename in $(find "$1" -iname "*.*"); do
                filename=$(basename -- "$fullfilename")
                extension="${filename##*.}"
                filename="${filename%.*}"
                normalized="$1/$filename.normalized.$extension"

                normalize "$fullfilename" "$normalized"
        done
else
        normalize "$1" "$2"
fi