video_length()
{
    passlog=$(tempdir /tmp/ffmpeg2pass nocreate)
    outfile="/tmp/ffmpeg_out$(date +%s).mpg"
    ffmpeg -i "$1" -pass 1 -passlogfile "$passlog" -target dvd -y "$outfile" > /dev/null 2>&1
    awk -F'[: ]' 'END{print $2}' "${passlog}-0.log"
    rm -f "${passlog}-0.log" 2>&1
    rm -f "$outfile" 2>&1
}