#!/usr/bin/perl
# (c) 2008 torh@bogus.net
# 
# quick hack, needed to remove noise from RTP audio packets during a 
# security test.
#
$|=1;
$MAXREAD=12;
use Getopt::Long;

GetOptions("f","h","i=s" => \$infile,"o=s" => \$outfile);

if($opt_h) {
   print <<EOM;
$0 [-h|-f] -i <inputfile> -o <outputfile> || (c) 2008 torh\@bogus.net
 -h : this
 -f : force overwrite existing file
 -i : inputfile
 -o : outputfile
To use this tool, you need to acquire a RTP stream first; the easiest way to do
this is to capture UDP packets to/from port 5200 using tcpdump or Wireshark and
then "Follow UDP stream" using the latter tool. Save the stream as raw and point
this tool at that file (-i), then load the result (-o) in audacity as A-Law, 
mono, 8000Hz.
EOM
   exit;
}
print "$0 - a tool to convert nortel audio dumps - (c) 2008 torh\@bogus.net\n";

die "STOP: Need -i <filename>\n" unless($infile);
die "STOP: Need -o <filename>\n" unless($outfile);

if(-e $outfile) {
   die "STOP: Outfile exists. Force (-f) to override." unless($opt_f);
}

open(IN,"<$infile");
open(OUT,">$outfile");
binmode(IN);
# read the first 32 bytes of the file to determine packet header

$r=sysread(IN,$buf,12);
die "FAIL: Failed to read header, only $r bytes read (needed 12).\n" unless $r==12;

$ha = unpack("C",substr($buf,0,1));
$hb = unpack("C",substr($buf,1,1));
$ta = unpack("C",substr($buf,10,1));
$tb = unpack("C",substr($buf,11,1));
printf "header: %.2x%.2x xxxx xxxx xxxx xxxx ", $ha,$hb;
printf "%.2x%.2x\n",$ta,$tb;

$foo=0;
while(sysread(IN,$buf,$MAXREAD)) {
   for($i=0;$i<$MAXREAD;$i++) {

      ## find RTP header and strip it

      if((unpack("C",substr($buf,$i,1)) == $ha) && 
         (unpack("C",substr($buf,$i+1,1)) == $hb) &&
         (unpack("C",substr($buf,$i+10,1)) == $ta) &&
         (unpack("C",substr($buf,$i+11,1)) == $tb)) {
         print "header found, skipping to data" unless $foo;
         $foo=1;
         print ".";
         $i=$i+12;
      }
      print OUT substr($buf,$i,1);
   }
}

close(IN);
close(OUT);

print "DONE.\n"