Created convert.php file

<html>
<body bgcolor="Black" text="White">
<?php


error_reporting(E_ALL);

$convert_command = "/usr/bin/mencoder '/home/mmvideos/public_html/video/ristinamodel_balloons_2__2_.mpeg' -o /home/mmvideos/public_html/flvideo/119214297363517344.flv -of lavf -oac mp3lame -lameopts abr:br=56 -ovc lavc -lavcopts vcodec=flv:vbitrate=500:mbd=2:mv0:trell:v4mv:cbp:l ast_pred=3 -srate 22050 -ofps 24 -vf harddup";

$var = exec($convert_command,$exec_result);

echo "<pre>";
for($i=0;$i<count($exec_result);$i++){
echo $exec_result[$i] . "
";
}


?>
</body>
</html>

Can be found at http://mmvideos.org/convert.php
All I get is a black window

Please help at a loss here