#!/bin/bash

# help
if [ $# -eq 0 ]; then echo "Returns EBU r128 integrated loudness corection number for files"; exit 1; fi

# checks
ffmpeg -filters 2>/dev/null | grep -q 'EBU R128' || { echo "your ffmpeg doesn't have EBU R128 scanner, exiting." ; exit 1; }
command -v bc >/dev/null 2>&1 || { >&2 echo "I need bc calculator installed." ; exit 1; }

# main
while [ $# -gt 0 ]; do

    # "-t 300" ensures that no more than 5 minutes of file is scanned
    read -r _ r128 _ <<< "$(ffmpeg -nostats -i "$1" -t 300 -vn -filter_complex ebur128 -f null - 2>&1 | tail -10 | grep "I:")"
    # change this to whatever you want, default EBU value is -23
    correct=$(echo "(-23)-($r128)+6" | bc)
    echo "$correct"

shift
done