#!/usr/bin/perl
# this script is intended to fix a specific problem I found with my
# mythtv files that were captured by firewire.  It may be of value
# in other cases, but don't use this if you don't understand what it does.
# 
# this script seeks through the beginning of the file specified, until it
# finds four sequences where the TS sync byte is 188 bytes apart.  This is 
# probably Transport Stream, but the possibility exists that it is a 
# coincidence.
# 
# the original file will be saved with a .tsfixer extension.  If the new 
# file doesn't work, replace it with the orignal.
#
# Usage:  ./tsfixer.pl /path/to/file/file.nuv

$inputfile = $ARGV[0];

open TSfile, "$inputfile" or die  "Can't open $inputfile: $!\n";
binmode TSfile;

$i = 0;
$not_ts = 1;
$do_it = 0;

while (($i < 100000) && ($not_ts == 1)) {

	   $start_pos = tell(TSfile);
	   read(TSfile, $buf1, 1);
	   $buf_u = unpack('C*', $buf1);

	   if ($buf_u == 71){
		seek(TSfile, $start_pos +188, 0);
		read(TSfile, $buf2, 1);
		$buf_u2 = unpack('C*', $buf2);

		seek(TSfile, $start_pos +376, 0);
		read(TSfile, $buf3, 1);
		$buf_u3 = unpack('C*', $buf3);

		seek(TSfile, $start_pos +564, 0);
		read(TSfile, $buf4, 1);
		$buf_u4 = unpack('C*', $buf4);

		if(($buf_u2 == 71) && ($buf_u3 == 71) && ($buf_u4 == 71) && ($start_pos != 1)){
			$not_ts = 0;
			printf ("found TS at $i\n"); 
			if ($start_pos == 0){
				printf ("this file doesn't need fixing.\n");
			}else{

			$do_it = 1;
			}
		}
	
	   }else {
		$i++;
	   }

}

close TSfile;

if($do_it == 1){

	$outputfile = $inputfile;
	$moved_inputfile = "$inputfile" . ".tsfixer";
	rename $inputfile, $moved_inputfile or die  "Can't rename $inputfile: $!\n";

	open TSfile, "$moved_inputfile" or die  "Can't open $moved_inputfile: $!\n";
	binmode TSfile;

	seek(TSfile, $start_pos, 0);
	open TSoutfile, "> $outputfile" or die  "Can't open $outputfile: $!\n";
	binmode TSoutfile;
	while (<TSfile>){
	  print TSoutfile; 
	}
}

close TSfile;
close TSoutfile;