Now that Blu-ray has won the HiDef optical disc format war, what is Blu-ray anyway? Over on CoolGadgets there is a longish posting that provides a good overview, including a quick review of Blu-ray security technologies AACS, BD+, and ROM mark. ROM mark is an antipriracy feature that is a watermark on the physical disc so that players can check on the authenticity of the disc inserted in the drive and then refuse to play titles that lack the proper mark.