The engineers at Warner have been busy lately. Their latest quest: Why can't Blu-ray and HD DVD just get along? According to the NewScientist news service, Alan Bell and Lewis Ostrover have filed a patent for a disc that plays both of the nascent high-def formats as well as standard-def DVD. Getting the existing DVD format onto the disc was a cinch—it's simply the second side of a dual-sided disc. But how did they manage to get Blu-ray and HD DVD together onto the other layer? Two things worked in their favor. First, Blu-ray reads the disc at a relatively shallow 0.1mm, while HD DVD (like regular DVD) reads at a deeper 0.6mm. Second, they found a way to make the shallower Blu-ray layer act as a two-way mirror. It reflects enough light back to the laser to make the Blu-ray layer's data readable, but at the same time, lets through enough light to penetrate to the deeper HD DVD layer. Yet to be determined: How much will this three-format disc cost to manufacture? Will the hardware makers go for it, even assuming that the Blu-ray and HD DVD licensing powers allow them? And finally, and most crucial, will the studios and video retailers go for it? For the latter in particular, this could be the solution to the triple-inventory nightmare that threatens to strangle both Blu-ray and HD DVD.