function check_with_dvdauthor()
# usage ex. : for i in "${!IN_FILES[@]}; do
#    if ! check_with_dvdauthor >/dev/null 2>&1; then
#        do_something . . .
#    rm -fr "$OUT_DIR" etc etc
{
    if dvdauthor -h 2>&1 |grep -q -- "-n "; then
        dvdauthor -n -o $OUT_DIR -t "$1"
    else
        dvdauthor -o $OUT_DIR -t "$1"
    fi
}