adjust cropdetect skip interval according to video duration

#GET CROPVALUE
if [ ! $fflag ]; then
    #cropdetect runs 10 passes at X seconds intervals. it will fail if
    #interval secs x passes exceeds video duration so set short interval
    #for videos shorter than 30 mins & set long interval for others.
    ffmpeg -i "$i" 2>$FINFO
    DUR=$(grep -m 1 -e Duration $FINFO|awk -F ": " '{print $2}'|\
    awk -F ", " '{print $1}' |awk '{ split($1, A, ":"); print 3600*A[1] + 60*A[2] + A[3] }')
    DUR=$(printf %.0f\\n $DUR)
        if [ $DUR -lt 1800 ]; then
        SECS=15
        else
        SECS=180
        fi
    cropdetect
    else CROP=""
    ffprobe -show_streams "$i" &>$FINFO
    #WIDTH is needed if picture is to be scaled
    WIDTH=$(grep width $FINFO|awk -F "=" '{print $2}')
fi