adjust-volume

#!/bin/sh
#
# Copyright 2015 by Chris Osborn <fozztexx@fozztexx.com>
#
# This file is part of viddin.
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License at <http://www.gnu.org/licenses/> for
# more details.

set -e

VOLUME="-10"

while [ $# -gt 0 -a `expr substr "${1:-empty}" 1 2` = "--" ] ; do
    case "$1" in
	--volume)
	    VOLUME="$2"
	    shift 2
	    ;;
	*)
	    unknown flag "$1"
	    exit 1
	    ;;
    esac
done

SOURCE="$1"
DEST="$2"
TMP=/tmp/adjust.$$

if [ -z "${DEST}" ] ; then
    DEST="${SOURCE%.*}-adj"
    EXT="${SOURCE##*.}"
    while [ -e "${DEST}${COUNTER}.${EXT}" ] ; do
	if [ -z "${COUNTER}" ] ; then
	    COUNTER=1
	fi
	COUNTER=`expr ${COUNTER} + 1`
    done
    DEST="${DEST}${COUNTER}.${EXT}"
fi

echo -n "Scanning ${SOURCE}..."
ffmpeg -hide_banner -i "${SOURCE}" -filter:a volumedetect -vn -sn -f null /dev/null > ${TMP} 2>&1
MEAN=`grep mean_volume: ${TMP} | awk '{print $5}'`
MAX=`grep max_volume: ${TMP} | awk '{print $5}'`
OFFSET=`echo "scale = 6; ${VOLUME} - ${MAX}" | bc`
echo " ${MEAN} ${MAX} ${OFFSET}"

echo -n "Adjusting volume to ${OFFSET}..."
ffmpeg -hide_banner -loglevel panic -y -i "${SOURCE}" -af "volume=${OFFSET}dB" -c:v copy "${DEST}"
echo ''

rm -f ${TMP}