#!/usr/local/bin/perl -w
use strict;

open IN,  '< :raw', $ARGV[ 0 ] or die "$ARGV[ 0 ] : $!";
open OUT, '> :raw', $ARGV[ 1 ] or die "$ARGV[ 1 ] : $!";

my $buffer;
sysread IN, $buffer, 384, 384;
do{
	## Move the second half of the buffer to the front.
	$buffer = substr( $buffer, 384 );
	
	## and overwrite it with a new chunk
	sysread IN, $buffer, 384, length( $buffer );	
	
     ## Apply the regex
     $buffer =~ s[
     	\xF4 .		## The marker byte plus friend
     	( .{190} )  ## 1520 bits to retain
     	\xF4 .		## Second marker + friend
     	( .{58} )	## 464 bits to retain
     	.{132}		## 1056 bits to discard
     ][$1$2]xg;
     
     ## Write out the first half of the buffer
     syswrite OUT, $buffer, 384;
} until eof IN;

close IN;
close OUT;