将rmvb文件的metadata由GBK转换成UTF8

#!/usr/bin/perl

#this is to convert RMVB file's metadata from GBK to UTF8 encoding
#to use it:
#       convRmvbEncode fileName.rmvb
#
#************USE AT YOUR OWN RISK******************
#If the RMVB file has more than one DATA section, the result file
#may not be usable.

#The RMVB file format can be found at:
#http://wiki.multimedia.cx/index.php?title=RealMedia

use strict 'vars';

use Fcntl; #for random file control

use Encode qw/from_to/;

#*****************************************************
my $from_encoding = "GBK";    #old file's encoding
my $to_encoding = "UTF8";     #new file's encoding
#*****************************************************

my $rmvbFile = @ARGV[0];



my ($buffer); #temp variable


#-----------------------------------------------------
#the following to try to read CONT tag
#and covert the CONT tags to UTF8

my $changed_cont = ""; #cont section after coverting to UTF8
my $added_len = -1; #number of chars added to cont 
 #section after coverting to UTF8

my $num_headers = 0;
{
        open(HND_RMVB, "<$rmvbFile") 
 or die "Couldn't open $rmvbFile for overwriting: $!\n";
        binmode(HND_RMVB);

        #---------------------------------------------
        #try to read content tag of the rmvb file
        my ($cont_pos, $cont_size, $cont_ver, $cont_buffer) =
 (-1, -1, -1, "");
        
        #read first 18 bytes
        $buffer = "";
        read(HND_RMVB, $buffer, 18) == 18 or die "error when read:$!";

        my ($obj_id, $obj_size, $obj_version, $file_ver);

        ($obj_id, 
 $obj_size, 
 $obj_version,
 $file_ver,
 $num_headers) = unpack("a4NnNN", $buffer);

        #quit if not a real media file
        die "Not a Real Media file" if $obj_id ne ".RMF";

        for (my $i = 0; $i < $num_headers; $i ++){

 $buffer = "";
 read(HND_RMVB, $buffer, 10) == 10 
 or die "error when read:$!";

 ($obj_id, $obj_size, $obj_version) 
 = unpack("a4NH", $buffer);

 print "Header $i: $obj_id, $obj_size, $obj_version\n";

 if ($obj_id eq "CONT") {

 $cont_buffer = "";
 read(HND_RMVB, $cont_buffer, $obj_size - 10 ) 
 == $obj_size - 10
 or die "error when read:$!";

 $cont_pos = tell(HND_RMVB) - $obj_size;
 $cont_size = $obj_size;
 $cont_ver = $obj_version;

 }else{
 #skip other sections
 seek(HND_RMVB, 
 tell(HND_RMVB) + $obj_size - 10, 
 SEEK_SET);
 }

        }

        die "Couldn't find content tags" if ($cont_size == -1);
        #-------------------------------------------------------
        
        #the following will convert content tag to UTF encoding
        #------------------------------------------------------
        my ($title_len, $title);
        my ($author_len, $author);
        my ($copyright_len, $copyright);
        my ($comment_len, $comment);
        
        my $tmp_pos = 0;

        #read title
        $title_len = unpack("n", substr($cont_buffer,$tmp_pos, 2));
        $tmp_pos += 2;
        $title = substr($cont_buffer, $tmp_pos, $title_len);
        $tmp_pos += $title_len;

        #read author
        $author_len = unpack("n", substr($cont_buffer,$tmp_pos, 2));
        $tmp_pos += 2;
        $author = substr($cont_buffer, $tmp_pos, $author_len);
        $tmp_pos += $author_len;

        #read copyright
        $copyright_len = unpack("n", substr($cont_buffer,$tmp_pos, 2));
        $tmp_pos += 2;
        $copyright = substr($cont_buffer, $tmp_pos, $copyright_len);
        $tmp_pos += $copyright_len;

        #read comment
        $comment_len = unpack("n", substr($cont_buffer,$tmp_pos, 2));
        $tmp_pos += 2;
        $comment = substr($cont_buffer, $tmp_pos, $comment_len);
        $tmp_pos += $comment_len;

        print "------Before Change-------\n";
        print "title($title_len)=$title\n";
        print "author($author_len)=$author\n";
        print "copyright($copyright_len)=$copyright\n";
        print "comment($comment_len)=$comment\n";


        #convert to UTF8
        from_to($title, $from_encoding, $to_encoding);
        from_to($author, $from_encoding, $to_encoding);
        from_to($copyright, $from_encoding, $to_encoding);
        from_to($comment, $from_encoding, $to_encoding);


        print "------After Change-------\n";

        $title_len = length($title);
        $author_len = length($author);
        $copyright_len = length($copyright);
        $comment_len = length($comment);

        print "title($title_len)=$title\n";
        print "author($author_len)=$author\n";
        print "copyright($copyright_len)=$copyright\n";
        print "comment($comment_len)=$comment\n";
 
        #rebuid CONT section
        $changed_cont = pack 
 "a4 N n na$title_len na$author_len na$copyright_len na$comment_len",
 "CONT",
 10 + 
 2 + $title_len +
 2 + $author_len +
 2 + $copyright_len +
 2 + $comment_len,
 $cont_ver,
 $title_len, $title,
 $author_len, $author,
 $copyright_len, $copyright,
 $comment_len, $comment
 ;
 
        $added_len = length($changed_cont) - $cont_size;        
        
        close (HND_RMVB);

}
#----------------------------------------------------------

#confirm with user if want to make the change
print "This Real Media file may have multiple DATA sections, output file may not be usable\n" if ($num_headers > 7);
print "Make the change?(Y/N)\n";
my $user_in=<STDIN>;
$user_in = uc($user_in);

my $newFileCreated = 0;

if (substr($user_in,0,1) ne "Y"){

        print "File not changed\n";

}else{

        open(HND_RMVB, "<$rmvbFile") 
 or die "Couldn't open $rmvbFile for overwriting: $!\n";
        binmode(HND_RMVB);

        #create a new file
        open(NEW_RMVB, ">$rmvbFile.new") 
 or die "error when creating new file:$!";
        binmode(NEW_RMVB);

        #copy the old file's first 18 bytes
        $buffer = "";
        read(HND_RMVB, $buffer, 18) == 18
 or die "Couldn't read: $!";
 
        print NEW_RMVB $buffer;
        
        my ($obj_id, 
 $obj_size, 
 $obj_version,
 $file_ver,
 $num_headers) = unpack("a4NnNN", $buffer);

        #print "$obj_id, $obj_size, $obj_version, $file_ver, $num_headers\n";

        for (my $i = 0; $i < $num_headers; $i ++){

 $buffer = "";
 read(HND_RMVB, $buffer, 10) == 10 
 or die "error when read:$!";

 ($obj_id, $obj_size, $obj_version) 
 = unpack("a4NH", $buffer);

 #print "Header $i: $obj_id, $obj_size, $obj_version\n";

 if ($obj_id eq "CONT") {

 print NEW_RMVB $changed_cont;
 
 #skip old file's CONT section
 seek(HND_RMVB, 
 tell(HND_RMVB) + $obj_size - 10, 
 SEEK_SET);
 
 }elsif ($obj_id eq "PROP"){

 #rebuid PROP section
 #need to recalculate offset of DATA section
 print NEW_RMVB $buffer; 
 
 $buffer = "";
 read(HND_RMVB, $buffer, $obj_size - 10);

 my ($maxBit, $avgBit, $lagData, $avgData,
 $nOfPcks, $duration, $sugNofMs, $offsetIndx,
 $offsetData, $nOfsteam, $flag) =
 unpack("NNNNNNNNNnn", $buffer);
 
 $buffer = "";
 $buffer = pack("NNNNNNNNNnn",
 $maxBit, 
 $avgBit, 
 $lagData, 
 $avgData,
 $nOfPcks, 
 $duration, 
 $sugNofMs, 
 $offsetIndx + $added_len,
 $offsetData + $added_len, 
 $nOfsteam, 
 $flag
 );
        
 print NEW_RMVB $buffer;
 
 }else{
 
 #for other sections, just copy
 
 #copy the header already read
 print NEW_RMVB $buffer; 
 
 #copy the rest of this section
 $buffer = "";
 read(HND_RMVB, $buffer, $obj_size - 10);
 print NEW_RMVB $buffer; 
 
 }
        }
        
        close (HND_RMVB);
        close (NEW_RMVB);
        
        rename($rmvbFile, "$rmvbFile.old") or die "Can't rename: $!";
        rename("$rmvbFile.new", "$rmvbFile") or die "Can't rename: $!";
}