<?php
$reqfile = "path/to/file.3gp";
$contenttype="audio/3gpp";
 
if($fn=fopen($reqfile, "rba")){
  header("Content-Type: ".$contenttype); 
  header("Content-Length: ".filesize($reqfile)); 
  header("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT");
  header("Pragma: no-cache");
  header("Expires: Mon, 26 Jul 1997 06:00:00 GMT");
  header("Cache-Control: no-store, no-cache, must-revalidate, max-age=0, post-check=0, pre-check=0");
passthru("ffmpeg -i 2012-09-29-1348911268.34-demo.wav -ar 8000 -ab 4.75k -");
  fpassthru($fn);
  fclose($fn);
}else{
  exit("error....");
}
exit();
?>