hi

the gc or any other similar optical drive (i.e. DVD drive) do NOT read any "barcodes" on the media (mini-DVD, 1.3GB). the only readable surface is the >read/write-surface on the disc, starting from the >boot sector.
the drive inside gc is a DVD optical drive, capable of reading ANY DVD.. executing the code on the disc.. that´s another story. (>booting from the disc)