Time-lapse video with mplayer and mencoder

#! /bin/bash
# Time-lapse capture script
# Author : Samuel El-Borai
# Date : 29 juin 2010
# Tested with : The iSight of my MacBook Pro 5.1, ArchGNULinux kernel 2.6.34.
#       Both camera of my N900, running Maemo PR 1.2
# Need : mplayer , mencoder
# Lisense : BSD

if test $# -ne 2; then
    echo 'Need two arguments : time(seconds) and frames(integer)'
    exit 0
fi

if test $1 -eq 0; then
    echo 'Time value must be greater than 0'
    exit 0
fi


if test $2 -eq 0; then
    echo 'Frames value must be greater than 0'
    exit 0
fi

#Change nb_frame (1-9) if you have green pictures.
nb_frame=3
t=$1

echo $f

rep='motion_'$(date '+%y%m%d%H')

mkdir $rep
cd $rep

for i in `seq 1 $2`;
do
    mplayer -really-quiet tv:// -vo png -frames $nb_frame;
        case ${#i} in
            1) n='0000'$i;;
            2) n='000'$i;;
            3) n='00'$i;;
            4) n='0'$i;;
            5) n=$i;;
            *) echo "More than 99999 frames. Hug ! It's over NINE THOUSAND !!! (This script can't manage more than 99999 frames. Sorry Dude.)"
                exit 0;;
        esac

        echo $n
    mv 0000000$nb_frame.png screen_$n.png
    rm 0*.png

# Time to echo remaining (Change time_to_echo to the minimum time you want between each echo)
    time_to_echo=10
    w=0

    if test $t -gt $time_to_echo
    then
        while test $(expr $w + $time_to_echo) -lt $t
        do
            sleep $time_to_echo
            w=$(expr $w + $time_to_echo)
            echo $(expr $t - $w)' seconds to wait'
        done
        #echo 'I will sleep '$(expr $t - $w)' seconds. TEST STATEMENT zOLOL RULEZ'
        sleep $(expr $t - $w)
    else
        sleep $t
    fi
    echo 'Frames '$i' / '$2
done

mencoder "mf://*.png" -mf fps=12:type=png -ovc lavc -lavcopts vcodec=mpeg4:mbd=2:trell:vbitrate=7000 -vf scale=640:480 -oac copy -o movie_$rep.avi

exit 0