my $rsize = pack("V4", $new_riff_size); # "V4" means Vax or Intel "little endian"
substr($buff,4,4) = substr($rsize,0,4);
my $data_size = pack("V4", $new_data_size);
substr($buff,54,4)= substr($data_size,0,4);
print OUTBIN substr($buff,0,58);