Something

<?
//You may need to provide the full path to ls
//If your web-server user has no environment 'path'
$line1 = exec('/usr/bin/ffmpeg -i test.mpg -ar 44100 -y video/temp/test.flv -s 320x240 -r 25', $output, $error);
while (list(,$line) = each($output)){
  echo $line, "<BR>\n";
}
if ($error){
  echo "Unix error code: $error<BR>\n";
  exit;
}


?>